Synthesize a nested VM-Exit if L2 triggers an emulated triple fault
instead of exiting to userspace, which likely will kill L1.  Any flow
that does KVM_REQ_TRIPLE_FAULT is suspect, but the most common scenario
for L2 killing L1 is if L0 (KVM) intercepts a contributory exception that
is _not_intercepted by L1.  E.g. if KVM is intercepting #GPs for the
VMware backdoor, a #GP that occurs in L2 while vectoring an injected #DF
will cause KVM to emulate triple fault.

Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Jim Mattson <jmattson@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210302174515.2812275-2-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Unexport the MMU load and unload helpers now that they are no longer
used (incorrectly) in vendor code.

Opportunistically move the kvm_mmu_sync_roots() declaration into mmu.h,
it should not be exposed to vendor code.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-16-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The new per-cpu stat 'nested_run' is introduced in order to track if L1 VM
is running or used to run L2 VM.

An example of the usage of 'nested_run' is to help the host administrator
to easily track if any L1 VM is used to run L2 VM. Suppose there is issue
that may happen with nested virtualization, the administrator will be able
to easily narrow down and confirm if the issue is due to nested
virtualization via 'nested_run'. For example, whether the fix like
commit 88dddc11 ("KVM: nVMX: do not use dangling shadow VMCS after
guest reset") is required.

Cc: Joe Jin <joe.jin@oracle.com>
Signed-off-by: NDongli Zhang <dongli.zhang@oracle.com>
Message-Id: <20210305225747.7682-1-dongli.zhang@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This patch adds the annotation to fix the following sparse errors:
arch/x86/kvm//x86.c:8147:15: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//x86.c:8147:15:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//x86.c:8147:15:    struct kvm_apic_map *
arch/x86/kvm//x86.c:10628:16: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//x86.c:10628:16:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//x86.c:10628:16:    struct kvm_apic_map *
arch/x86/kvm//x86.c:10629:15: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//x86.c:10629:15:    struct kvm_pmu_event_filter [noderef] __rcu *
arch/x86/kvm//x86.c:10629:15:    struct kvm_pmu_event_filter *
arch/x86/kvm//lapic.c:267:15: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//lapic.c:267:15:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//lapic.c:267:15:    struct kvm_apic_map *
arch/x86/kvm//lapic.c:269:9: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//lapic.c:269:9:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//lapic.c:269:9:    struct kvm_apic_map *
arch/x86/kvm//lapic.c:637:15: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//lapic.c:637:15:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//lapic.c:637:15:    struct kvm_apic_map *
arch/x86/kvm//lapic.c:994:15: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//lapic.c:994:15:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//lapic.c:994:15:    struct kvm_apic_map *
arch/x86/kvm//lapic.c:1036:15: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//lapic.c:1036:15:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//lapic.c:1036:15:    struct kvm_apic_map *
arch/x86/kvm//lapic.c:1173:15: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//lapic.c:1173:15:    struct kvm_apic_map [noderef] __rcu *
arch/x86/kvm//lapic.c:1173:15:    struct kvm_apic_map *
arch/x86/kvm//pmu.c:190:18: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//pmu.c:190:18:    struct kvm_pmu_event_filter [noderef] __rcu *
arch/x86/kvm//pmu.c:190:18:    struct kvm_pmu_event_filter *
arch/x86/kvm//pmu.c:251:18: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//pmu.c:251:18:    struct kvm_pmu_event_filter [noderef] __rcu *
arch/x86/kvm//pmu.c:251:18:    struct kvm_pmu_event_filter *
arch/x86/kvm//pmu.c:522:18: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//pmu.c:522:18:    struct kvm_pmu_event_filter [noderef] __rcu *
arch/x86/kvm//pmu.c:522:18:    struct kvm_pmu_event_filter *
arch/x86/kvm//pmu.c:522:18: error: incompatible types in comparison expression (different address spaces):
arch/x86/kvm//pmu.c:522:18:    struct kvm_pmu_event_filter [noderef] __rcu *
arch/x86/kvm//pmu.c:522:18:    struct kvm_pmu_event_filter *
Signed-off-by: NMuhammad Usama Anjum <musamaanjum@gmail.com>
Message-Id: <20210305191123.GA497469@LEGION>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This is how Xen guests do steal time accounting. The hypervisor records
the amount of time spent in each of running/runnable/blocked/offline
states.

In the Xen accounting, a vCPU is still in state RUNSTATE_running while
in Xen for a hypercall or I/O trap, etc. Only if Xen explicitly schedules
does the state become RUNSTATE_blocked. In KVM this means that even when
the vCPU exits the kvm_run loop, the state remains RUNSTATE_running.

The VMM can explicitly set the vCPU to RUNSTATE_blocked by using the
KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT attribute, and can also use
KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST to retrospectively add a given
amount of time to the blocked state and subtract it from the running
state.

The state_entry_time corresponds to get_kvmclock_ns() at the time the
vCPU entered the current state, and the total times of all four states
should always add up to state_entry_time.
Co-developed-by: NJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: NJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20210301125309.874953-2-dwmw2@infradead.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The 'mmu_page_hash' is used as hash table while 'active_mmu_pages' is a
list. Remove the misplaced comment as it's mostly stating the obvious
anyways.
Signed-off-by: NDongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210226061945.1222-1-dongli.zhang@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Remove several exports from the MMU that are no longer necessary.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-15-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Stop setting dirty bits for MMU pages when dirty logging is disabled for
a memslot, as PML is now completely disabled when there are no memslots
with dirty logging enabled.

This means that spurious PML entries will be created for memslots with
dirty logging disabled if at least one other memslot has dirty logging
enabled.  However, spurious PML entries are already possible since
dirty bits are set only when a dirty logging is turned off, i.e. memslots
that are never dirty logged will have dirty bits cleared.

In the end, it's faster overall to eat a few spurious PML entries in the
window where dirty logging is being disabled across all memslots.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-13-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Currently, if enable_pml=1 PML remains enabled for the entire lifetime
of the VM irrespective of whether dirty logging is enable or disabled.
When dirty logging is disabled, all the pages of the VM are manually
marked dirty, so that PML is effectively non-operational.  Setting
the dirty bits is an expensive operation which can cause severe MMU
lock contention in a performance sensitive path when dirty logging is
disabled after a failed or canceled live migration.

Manually setting dirty bits also fails to prevent PML activity if some
code path clears dirty bits, which can incur unnecessary VM-Exits.

In order to avoid this extra overhead, dynamically enable/disable PML
when dirty logging gets turned on/off for the first/last memslot.
Signed-off-by: NMakarand Sonare <makarandsonare@google.com>
Co-developed-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-12-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Drop the facade of KVM's PML logic being vendor specific and move the
bits that aren't truly VMX specific into common x86 code.  The MMU logic
for dealing with PML is tightly coupled to the feature and to VMX's
implementation, bouncing through kvm_x86_ops obfuscates the code without
providing any meaningful separation of concerns or encapsulation.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-10-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Store the vendor-specific dirty log size in a variable, there's no need
to wrap it in a function since the value is constant after
hardware_setup() runs.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-9-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Hyper-V emulation is enabled in KVM unconditionally. This is bad at least
from security standpoint as it is an extra attack surface. Ideally, there
should be a per-VM capability explicitly enabled by VMM but currently it
is not the case and we can't mandate one without breaking backwards
compatibility. We can, however, check guest visible CPUIDs and only enable
Hyper-V emulation when "Hv#1" interface was exposed in
HYPERV_CPUID_INTERFACE.

Note, VMMs are free to act in any sequence they like, e.g. they can try
to set MSRs first and CPUIDs later so we still need to allow the host
to read/write Hyper-V specific MSRs unconditionally.
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210126134816.1880136-14-vkuznets@redhat.com>
[Add selftest vcpu_set_hv_cpuid API to avoid breaking xen_vmcall_test. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Hyper-V context is only needed for guests which use Hyper-V emulation in
KVM (e.g. Windows/Hyper-V guests). 'struct kvm_vcpu_hv' is, however, quite
big, it accounts for more than 1/4 of the total 'struct kvm_vcpu_arch'
which is also quite big already. This all looks like a waste.

Allocate 'struct kvm_vcpu_hv' dynamically. This patch does not bring any
(intentional) functional change as we still allocate the context
unconditionally but it paves the way to doing that only when needed.
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210126134816.1880136-13-vkuznets@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Current KVM_USER_MEM_SLOTS limits are arch specific (512 on Power, 509 on x86,
32 on s390, 16 on MIPS) but they don't really need to be. Memory slots are
allocated dynamically in KVM when added so the only real limitation is
'id_to_index' array which is 'short'. We don't have any other
KVM_MEM_SLOTS_NUM/KVM_USER_MEM_SLOTS-sized statically defined structures.

Low KVM_USER_MEM_SLOTS can be a limiting factor for some configurations.
In particular, when QEMU tries to start a Windows guest with Hyper-V SynIC
enabled and e.g. 256 vCPUs the limit is hit as SynIC requires two pages per
vCPU and the guest is free to pick any GFN for each of them, this fragments
memslots as QEMU wants to have a separate memslot for each of these pages
(which are supposed to act as 'overlay' pages).
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210127175731.2020089-3-vkuznets@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

kvm_get_dr and emulator_get_dr except an in-range value for the register
number so they cannot fail.  Change the return type to void.
Suggested-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The TDP MMU assumes that it can do atomic accesses to 64-bit PTEs.
Rather than just disabling it, compile it out completely so that it
is possible to use for example 64-bit xchg.

To limit the number of stubs, wrap all accesses to tdp_mmu_enabled
or tdp_mmu_page with a function.  Calls to all other functions in
tdp_mmu.c are eliminated and do not even reach the linker.
Reviewed-by: NSean Christopherson <seanjc@google.com>
Tested-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Rename cr3_lm_rsvd_bits to reserved_gpa_bits, and use it for all GPA
legality checks.  AMD's APM states:

  If the C-bit is an address bit, this bit is masked from the guest
  physical address when it is translated through the nested page tables.

Thus, any access that can conceivably be run through NPT should ignore
the C-bit when checking for validity.

For features that KVM emulates in software, e.g. MTRRs, there is no
clear direction in the APM for how the C-bit should be handled.  For
such cases, follow the SME behavior inasmuch as possible, since SEV is
is essentially a VM-specific variant of SME.  For SME, the APM states:

  In this case the upper physical address bits are treated as reserved
  when the feature is enabled except where otherwise indicated.

Collecting the various relavant SME snippets in the APM and cross-
referencing the omissions with Linux kernel code, this leaves MTTRs and
APIC_BASE as the only flows that KVM emulates that should _not_ ignore
the C-bit.

Note, this means the reserved bit checks in the page tables are
technically broken.  This will be remedied in a future patch.

Although the page table checks are technically broken, in practice, it's
all but guaranteed to be irrelevant.  NPT is required for SEV, i.e.
shadowing page tables isn't needed in the common case.  Theoretically,
the checks could be in play for nested NPT, but it's extremely unlikely
that anyone is running nested VMs on SEV, as doing so would require L1
to expose sensitive data to L0, e.g. the entire VMCB.  And if anyone is
running nested VMs, L0 can't read the guest's encrypted memory, i.e. L1
would need to put its NPT in shared memory, in which case the C-bit will
never be set.  Or, L1 could use shadow paging, but again, if L0 needs to
read page tables, e.g. to load PDPTRs, the memory can't be encrypted if
L1 has any expectation of L0 doing the right thing.

Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210204000117.3303214-8-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

It turns out that we can't handle event channels *entirely* in userspace
by delivering them as ExtINT, because KVM is a bit picky about when it
accepts ExtINT interrupts from a legacy PIC. The in-kernel local APIC
has to have LVT0 configured in APIC_MODE_EXTINT and unmasked, which
isn't necessarily the case for Xen guests especially on secondary CPUs.

To cope with this, add kvm_xen_get_interrupt() which checks the
evtchn_pending_upcall field in the Xen vcpu_info, and delivers the Xen
upcall vector (configured by KVM_XEN_ATTR_TYPE_UPCALL_VECTOR) if it's
set regardless of LAPIC LVT0 configuration. This gives us the minimum
support we need for completely userspace-based implementation of event
channels.

This does mean that vcpu_enter_guest() needs to check for the
evtchn_pending_upcall flag being set, because it can't rely on someone
having set KVM_REQ_EVENT unless we were to add some way for userspace to
do so manually.
Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>

Allow the Xen emulated guest the ability to register secondary
vcpu time information. On Xen guests this is used in order to be
mapped to userspace and hence allow vdso gettimeofday to work.
Signed-off-by: NJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>

The vcpu info supersedes the per vcpu area of the shared info page and
the guest vcpus will use this instead.
Signed-off-by: NJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: NAnkur Arora <ankur.a.arora@oracle.com>
Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>

Add KVM_XEN_ATTR_TYPE_SHARED_INFO to allow hypervisor to know where the
guest's shared info page is.
Signed-off-by: NJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>

Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>

Add a new exit reason for emulator to handle Xen hypercalls.

Since this means KVM owns the ABI, dispense with the facility for the
VMM to provide its own copy of the hypercall pages; just fill them in
directly using VMCALL/VMMCALL as we do for the Hyper-V hypercall page.

This behaviour is enabled by a new INTERCEPT_HCALL flag in the
KVM_XEN_HVM_CONFIG ioctl structure, and advertised by the same flag
being returned from the KVM_CAP_XEN_HVM check.

Rename xen_hvm_config() to kvm_xen_write_hypercall_page() and move it
to the nascent xen.c while we're at it, and add a test case.
Signed-off-by: NJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>

To prepare for handling page faults in parallel, change the TDP MMU
page fault handler to use atomic operations to set SPTEs so that changes
are not lost if multiple threads attempt to modify the same SPTE.
Reviewed-by: NPeter Feiner <pfeiner@google.com>
Signed-off-by: NBen Gardon <bgardon@google.com>

Message-Id: <20210202185734.1680553-21-bgardon@google.com>
[Document new locking rules. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add a read / write lock to be used in place of the MMU spinlock on x86.
The rwlock will enable the TDP MMU to handle page faults, and other
operations in parallel in future commits.
Reviewed-by: NPeter Feiner <pfeiner@google.com>
Signed-off-by: NBen Gardon <bgardon@google.com>

Message-Id: <20210202185734.1680553-19-bgardon@google.com>
[Introduce virt/kvm/mmu_lock.h - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Convert kvm_x86_ops to use static calls. Note that all kvm_x86_ops are
covered here except for 'pmu_ops and 'nested ops'.

Here are some numbers running cpuid in a loop of 1 million calls averaged
over 5 runs, measured in the vm (lower is better).

Intel Xeon 3000MHz:

           |default    |mitigations=off
-------------------------------------
vanilla    |.671s      |.486s
static call|.573s(-15%)|.458s(-6%)

AMD EPYC 2500MHz:

           |default    |mitigations=off
-------------------------------------
vanilla    |.710s      |.609s
static call|.664s(-6%) |.609s(0%)

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: NJason Baron <jbaron@akamai.com>
Message-Id: <e057bf1b8a7ad15652df6eeba3f907ae758d3399.1610680941.git.jbaron@akamai.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Use static calls to improve kvm_x86_ops performance. Introduce the
definitions that will be used by a subsequent patch to actualize the
savings. Add a new kvm-x86-ops.h header that can be used for the
definition of static calls. This header is also intended to be
used to simplify the defition of svm_kvm_ops and vmx_x86_ops.

Note that all functions in kvm_x86_ops are covered here except for
'pmu_ops' and 'nested ops'. I think they can be covered by static
calls in a simlilar manner, but were omitted from this series to
reduce scope and because I don't think they have as large of a
performance impact.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: NJason Baron <jbaron@akamai.com>
Message-Id: <e5cc82ead7ab37b2dceb0837a514f3f8bea4f8d1.1610680941.git.jbaron@akamai.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

DR6_INIT contains the 1-reserved bits as well as the bit that is cleared
to 0 when the condition (e.g. RTM) happens. The value can be used to
initialize dr6 and also be the XOR mask between the #DB exit
qualification (or payload) and DR6.

Concerning that DR6_INIT is used as initial value only once, rename it
to DR6_ACTIVE_LOW and apply it in other places, which would make the
incoming changes for bus lock debug exception more simple.
Signed-off-by: NChenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090433.13441-2-chenyi.qiang@intel.com>
[Define DR6_FIXED_1 from DR6_ACTIVE_LOW and DR6_VOLATILE. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Virtual Machine can exploit bus locks to degrade the performance of
system. Bus lock can be caused by split locked access to writeback(WB)
memory or by using locks on uncacheable(UC) memory. The bus lock is
typically >1000 cycles slower than an atomic operation within a cache
line. It also disrupts performance on other cores (which must wait for
the bus lock to be released before their memory operations can
complete).

To address the threat, bus lock VM exit is introduced to notify the VMM
when a bus lock was acquired, allowing it to enforce throttling or other
policy based mitigations.

A VMM can enable VM exit due to bus locks by setting a new "Bus Lock
Detection" VM-execution control(bit 30 of Secondary Processor-based VM
execution controls). If delivery of this VM exit was preempted by a
higher priority VM exit (e.g. EPT misconfiguration, EPT violation, APIC
access VM exit, APIC write VM exit, exception bitmap exiting), bit 26 of
exit reason in vmcs field is set to 1.

In current implementation, the KVM exposes this capability through
KVM_CAP_X86_BUS_LOCK_EXIT. The user can get the supported mode bitmap
(i.e. off and exit) and enable it explicitly (disabled by default). If
bus locks in guest are detected by KVM, exit to user space even when
current exit reason is handled by KVM internally. Set a new field
KVM_RUN_BUS_LOCK in vcpu->run->flags to inform the user space that there
is a bus lock detected in guest.

Document for Bus Lock VM exit is now available at the latest "Intel
Architecture Instruction Set Extensions Programming Reference".

Document Link:
https://software.intel.com/content/www/us/en/develop/download/intel-architecture-instruction-set-extensions-programming-reference.htmlCo-developed-by: NXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: NXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: NChenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20201106090315.18606-4-chenyi.qiang@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Remove the update_pte() shadow paging logic, which was obsoleted by
commit 4731d4c7 ("KVM: MMU: out of sync shadow core"), but never
removed.  As pointed out by Yu, KVM never write protects leaf page
tables for the purposes of shadow paging, and instead marks their
associated shadow page as unsync so that the guest can write PTEs at
will.

The update_pte() path, which predates the unsync logic, optimizes COW
scenarios by refreshing leaf SPTEs when they are written, as opposed to
zapping the SPTE, restarting the guest, and installing the new SPTE on
the subsequent fault.  Since KVM no longer write-protects leaf page
tables, update_pte() is unreachable and can be dropped.
Reported-by: NYu Zhang <yu.c.zhang@intel.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210115004051.4099250-1-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Typically under KVM, an AP is booted using the INIT-SIPI-SIPI sequence,
where the guest vCPU register state is updated and then the vCPU is VMRUN
to begin execution of the AP. For an SEV-ES guest, this won't work because
the guest register state is encrypted.

Following the GHCB specification, the hypervisor must not alter the guest
register state, so KVM must track an AP/vCPU boot. Should the guest want
to park the AP, it must use the AP Reset Hold exit event in place of, for
example, a HLT loop.

First AP boot (first INIT-SIPI-SIPI sequence):
  Execute the AP (vCPU) as it was initialized and measured by the SEV-ES
  support. It is up to the guest to transfer control of the AP to the
  proper location.

Subsequent AP boot:
  KVM will expect to receive an AP Reset Hold exit event indicating that
  the vCPU is being parked and will require an INIT-SIPI-SIPI sequence to
  awaken it. When the AP Reset Hold exit event is received, KVM will place
  the vCPU into a simulated HLT mode. Upon receiving the INIT-SIPI-SIPI
  sequence, KVM will make the vCPU runnable. It is again up to the guest
  to then transfer control of the AP to the proper location.

  To differentiate between an actual HLT and an AP Reset Hold, a new MP
  state is introduced, KVM_MP_STATE_AP_RESET_HOLD, which the vCPU is
  placed in upon receiving the AP Reset Hold exit event. Additionally, to
  communicate the AP Reset Hold exit event up to userspace (if needed), a
  new exit reason is introduced, KVM_EXIT_AP_RESET_HOLD.

A new x86 ops function is introduced, vcpu_deliver_sipi_vector, in order
to accomplish AP booting. For VMX, vcpu_deliver_sipi_vector is set to the
original SIPI delivery function, kvm_vcpu_deliver_sipi_vector(). SVM adds
a new function that, for non SEV-ES guests, invokes the original SIPI
delivery function, kvm_vcpu_deliver_sipi_vector(), but for SEV-ES guests,
implements the logic above.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <e8fbebe8eb161ceaabdad7c01a5859a78b424d5e.1609791600.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The tdp_mmu_roots and tdp_mmu_pages in struct kvm_arch should only contain
pages with tdp_mmu_page set to true. tdp_mmu_pages should not contain any
pages with a non-zero root_count and tdp_mmu_roots should only contain
pages with a positive root_count, unless a thread holds the MMU lock and
is in the process of modifying the list. Various functions expect these
invariants to be maintained, but they are not explictily documented. Add
to the comments on both fields to document the above invariants.
Signed-off-by: NBen Gardon <bgardon@google.com>
Message-Id: <20210107001935.3732070-2-bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The guest FPU state is automatically restored on VMRUN and saved on VMEXIT
by the hardware, so there is no reason to do this in KVM. Eliminate the
allocation of the guest_fpu save area and key off that to skip operations
related to the guest FPU state.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <173e429b4d0d962c6a443c4553ffdaf31b7665a4.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

SEV-ES guests do not currently support SMM. Update the has_emulated_msr()
kvm_x86_ops function to take a struct kvm parameter so that the capability
can be reported at a VM level.

Since this op is also called during KVM initialization and before a struct
kvm instance is available, comments will be added to each implementation
of has_emulated_msr() to indicate the kvm parameter can be null.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <75de5138e33b945d2fb17f81ae507bda381808e3.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

For SEV-ES guests, the interception of control register write access
is not recommended. Control register interception occurs prior to the
control register being modified and the hypervisor is unable to modify
the control register itself because the register is located in the
encrypted register state.

SEV-ES guests introduce new control register write traps. These traps
provide intercept support of a control register write after the control
register has been modified. The new control register value is provided in
the VMCB EXITINFO1 field, allowing the hypervisor to track the setting
of the guest control registers.

Add support to track the value of the guest CR4 register using the control
register write trap so that the hypervisor understands the guest operating
mode.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <c3880bf2db8693aa26f648528fbc6e967ab46e25.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

For SEV-ES guests, the interception of control register write access
is not recommended. Control register interception occurs prior to the
control register being modified and the hypervisor is unable to modify
the control register itself because the register is located in the
encrypted register state.

SEV-ES support introduces new control register write traps. These traps
provide intercept support of a control register write after the control
register has been modified. The new control register value is provided in
the VMCB EXITINFO1 field, allowing the hypervisor to track the setting
of the guest control registers.

Add support to track the value of the guest CR0 register using the control
register write trap so that the hypervisor understands the guest operating
mode.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <182c9baf99df7e40ad9617ff90b84542705ef0d7.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

For an SEV-ES guest, string-based port IO is performed to a shared
(un-encrypted) page so that both the hypervisor and guest can read or
write to it and each see the contents.

For string-based port IO operations, invoke SEV-ES specific routines that
can complete the operation using common KVM port IO support.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <9d61daf0ffda496703717218f415cdc8fd487100.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This will be used by SEV-ES to inject MSR failure via the GHCB.
Reviewed-by: NTom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Allocate a page during vCPU creation to be used as the encrypted VM save
area (VMSA) for the SEV-ES guest. Provide a flag in the kvm_vcpu_arch
structure that indicates whether the guest state is protected.

When freeing a VMSA page that has been encrypted, the cache contents must
be flushed using the MSR_AMD64_VM_PAGE_FLUSH before freeing the page.

[ i386 build warnings ]
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <fde272b17eec804f3b9db18c131262fe074015c5.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

kvm_cpu_accept_dm_intr and kvm_vcpu_ready_for_interrupt_injection are
a hodge-podge of conditions, hacked together to get something that
more or less works.  But what is actually needed is much simpler;
in both cases the fundamental question is, do we have a place to stash
an interrupt if userspace does KVM_INTERRUPT?

In userspace irqchip mode, that is !vcpu->arch.interrupt.injected.
Currently kvm_event_needs_reinjection(vcpu) covers it, but it is
unnecessarily restrictive.

In split irqchip mode it's a bit more complicated, we need to check
kvm_apic_accept_pic_intr(vcpu) (the IRQ window exit is basically an INTACK
cycle and thus requires ExtINTs not to be masked) as well as
!pending_userspace_extint(vcpu).  However, there is no need to
check kvm_event_needs_reinjection(vcpu), since split irqchip keeps
pending ExtINT state separate from event injection state, and checking
kvm_cpu_has_interrupt(vcpu) is wrong too since ExtINT has higher
priority than APIC interrupts.  In fact the latter fixes a bug:
when userspace requests an IRQ window vmexit, an interrupt in the
local APIC can cause kvm_cpu_has_interrupt() to be true and thus
kvm_vcpu_ready_for_interrupt_injection() to return false.  When this
happens, vcpu_run does not exit to userspace but the interrupt window
vmexits keep occurring.  The VM loops without any hope of making progress.

Once we try to fix these with something like

     return kvm_arch_interrupt_allowed(vcpu) &&
-        !kvm_cpu_has_interrupt(vcpu) &&
-        !kvm_event_needs_reinjection(vcpu) &&
-        kvm_cpu_accept_dm_intr(vcpu);
+        (!lapic_in_kernel(vcpu)
+         ? !vcpu->arch.interrupt.injected
+         : (kvm_apic_accept_pic_intr(vcpu)
+            && !pending_userspace_extint(v)));

we realize two things.  First, thanks to the previous patch the complex
conditional can reuse !kvm_cpu_has_extint(vcpu).  Second, the interrupt
window request in vcpu_enter_guest()

        bool req_int_win =
                dm_request_for_irq_injection(vcpu) &&
                kvm_cpu_accept_dm_intr(vcpu);

should be kept in sync with kvm_vcpu_ready_for_interrupt_injection():
it is unnecessary to ask the processor for an interrupt window
if we would not be able to return to userspace.  Therefore,
kvm_cpu_accept_dm_intr(vcpu) is basically !kvm_cpu_has_extint(vcpu)
ANDed with the existing check for masked ExtINT.  It all makes sense:

- we can accept an interrupt from userspace if there is a place
  to stash it (and, for irqchip split, ExtINTs are not masked).
  Interrupts from userspace _can_ be accepted even if right now
  EFLAGS.IF=0.

- in order to tell userspace we will inject its interrupt ("IRQ
  window open" i.e. kvm_vcpu_ready_for_interrupt_injection), both
  KVM and the vCPU need to be ready to accept the interrupt.

... and this is what the patch implements.
Reported-by: NDavid Woodhouse <dwmw@amazon.co.uk>
Analyzed-by: NDavid Woodhouse <dwmw@amazon.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NNikos Tsironis <ntsironis@arrikto.com>
Reviewed-by: NDavid Woodhouse <dwmw@amazon.co.uk>
Tested-by: NDavid Woodhouse <dwmw@amazon.co.uk>