The logic for calculating the value with which we call kvm_set_cr0/4 was
broken (will definitely be visible with nested unrestricted guest mode
support). Also, we performed the check regarding CR0_ALWAYSON too early
when in guest mode.

What really needs to be done on both CR0 and CR4 is to mask out L1-owned
bits and merge them in from L1's guest_cr0/4. In contrast, arch.cr0/4
and arch.cr0/4_guest_owned_bits contain the mangled L0+L1 state and,
thus, are not suited as input.

For both CRs, we can then apply the check against VMXON_CRx_ALWAYSON and
refuse the update if it fails. To be fully consistent, we implement this
check now also for CR4. For CR4, we move the check into vmx_set_cr4
while we keep it in handle_set_cr0. This is because the CR0 checks for
vmxon vs. guest mode will diverge soon when adding unrestricted guest
mode support.

Finally, we have to set the shadow to the value L2 wanted to write
originally.
Reviewed-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Properly set those bits to 1 that the spec demands in case bit 55 of
VMX_BASIC is 0 - like in our case.
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Ouch, how could this work so well that far? We need to clear RFLAGS to
the reset value as specified by the SDM. Particularly, IF must be off
after VM-exit!
Reviewed-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

First of all, do not blindly overwrite GUEST_DR7 on L2 entry. The host
may have guest debugging enabled. Then properly reset DR7 and DEBUG_CTL
on L2->L1 switch as specified in the SDM.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Except ia64's stale code, KVM_SET_MEMORY_REGION support, this is only
used for sanity checks in __kvm_set_memory_region() which can easily
be changed to use slot id instead.
Signed-off-by: NTakuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Cleanup: __vmx_complete_interrupts has no use for the vmx structure.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

IDT_VECTORING_INFO_FIELD was already read right after vmexit.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

No need to re-read what vmx_vcpu_run already picked up for us.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

Switching the VMCS obviously invalidates what may have been cached about
the guest segments.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

These exits have no preconditions, and we already process the
corresponding reasons in nested_vmx_exit_handled correctly.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

Both are only used locally.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

This avoids basing decisions on uninitialized variables, potentially
leaking kernel data to the L1 guest.
Reviewed-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This prevents trapping L2 I/O exits if L1 has neither unconditional nor
bitmap-based exiting enabled. Furthermore, it implements I/O bitmap
handling.
Reviewed-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

We already pass vmcs12 as argument.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

Without Posted Interrupt, current code is broken. Just disable by
default until Posted Interrupt is ready.
Signed-off-by: NYang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

When calculating hw_cr0 teh current code masks bits that should be always
on and re-adds them back immediately after. Cleanup the code by masking
only those bits that should be dropped from hw_cr0. This allow us to
get rid of some defines.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

SMEP is disabled if CPU is in non-paging mode in hardware.
However KVM always uses paging mode to emulate guest non-paging
mode with TDP. To emulate this behavior, SMEP needs to be manually
disabled when guest switches to non-paging mode.

We met an issue that, SMP Linux guest with recent kernel (enable
SMEP support, for example, 3.5.3) would crash with triple fault if
setting unrestricted_guest=0. This is because KVM uses an identity
mapping page table to emulate the non-paging mode, where the page
table is set with USER flag. If SMEP is still enabled in this case,
guest will meet unhandlable page fault and then crash.
Reviewed-by: NGleb Natapov <gleb@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NDongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: NXiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Virtual interrupt delivery avoids KVM to inject vAPIC interrupts
manually, which is fully taken care of by the hardware. This needs
some special awareness into existing interrupr injection path:

- for pending interrupt, instead of direct injection, we may need
  update architecture specific indicators before resuming to guest.

- A pending interrupt, which is masked by ISR, should be also
  considered in above update action, since hardware will decide
  when to inject it at right time. Current has_interrupt and
  get_interrupt only returns a valid vector from injection p.o.v.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NKevin Tian <kevin.tian@intel.com>
Signed-off-by: NYang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

basically to benefit from apicv, we need to enable virtualized x2apic mode.
Currently, we only enable it when guest is really using x2apic.

Also, clear MSR bitmap for corresponding x2apic MSRs when guest enabled x2apic:
0x800 - 0x8ff: no read intercept for apicv register virtualization,
               except APIC ID and TMCCT which need software's assistance to
               get right value.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NKevin Tian <kevin.tian@intel.com>
Signed-off-by: NYang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

- APIC read doesn't cause VM-Exit
- APIC write becomes trap-like
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NKevin Tian <kevin.tian@intel.com>
Signed-off-by: NYang Zhang <yang.z.zhang@intel.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

If emulate_invalid_guest_state=false vmx->emulation_required is never
actually used, but it ends up to be always set to true since
handle_invalid_guest_state(), the only place it is reset back to
false, is never called. This, besides been not very clean, makes vmexit
and vmentry path to check emulate_invalid_guest_state needlessly.

The patch fixes that by keeping emulation_required coherent with
emulate_invalid_guest_state setting.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

The function deals with code segment too.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Usability is returned in unusable field, so not need to clobber entire
AR. Callers have to know how to deal with unusable segments already
since if emulate_invalid_guest_state=true AR is not zeroed.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

vmx->rmode.vm86_active is never true is unrestricted guest is enabled.
Make it more explicit that neither enter_pmode() nor enter_rmode() is
called in this case.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

There is no reason for it. If state is suitable for vmentry it
will be detected during guest entry and no emulation will happen.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Since vmx_get_cpl() always returns 0 when VCPU is in real mode it is no
longer needed. Also reset CPL cache to zero during transaction to
protected mode since transaction may happen while CS.selectors & 3 != 0,
but in reality CPL is 0.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

CPL is always 0 when in real mode, and always 3 when virtual 8086 mode.

Using values other than those can cause failures on operations that
check CPL.
Reviewed-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

With emulate_invalid_guest_state=0 if a vcpu is in real mode VMX can
enter the vcpu with smaller segment limit than guest configured.  If the
guest tries to access pass this limit it will get #GP at which point
instruction will be emulated with correct segment limit applied. If
during the emulation IO is detected it is not handled correctly. Vcpu
thread should exit to userspace to serve the IO, but it returns to the
guest instead.  Since emulation is not completed till userspace completes
the IO the faulty instruction is re-executed ad infinitum.

The patch fixes that by exiting to userspace if IO happens during
instruction emulation.
Reported-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Segment registers will be fixed according to current emulation policy
during switching to real mode for the first time.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Currently when emulation of invalid guest state is enable
(emulate_invalid_guest_state=1) segment registers are still fixed for
entry to vm86 mode some times. Segment register fixing is avoided in
enter_rmode(), but vmx_set_segment() still does it unconditionally.
The patch fixes it.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Currently it allows entering vm86 mode if segment limit is greater than
0xffff and db bit is set. Both of those can cause incorrect execution of
instruction by cpu since in vm86 mode limit will be set to 0xffff and db
will be forced to 0.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

Move all vm86_active logic into one place.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

Segment descriptor's base is fixed by call to fix_rmode_seg(). Not need
to do it twice.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

The code for SS and CS does the same thing fix_rmode_seg() is doing.
Use it instead of hand crafted code.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

VMX without unrestricted mode cannot virtualize real mode, so if
emulate_invalid_guest_state=0 kvm uses vm86 mode to approximate
it. Sometimes, when guest moves from protected mode to real mode, it
leaves segment descriptors in a state not suitable for use by vm86 mode
virtualization, so we keep shadow copy of segment descriptors for internal
use and load fake register to VMCS for guest entry to succeed. Till
now we kept shadow for all segments except SS and CS (for SS and CS we
returned parameters directly from VMCS), but since commit a5625189
emulator enforces segment limits in real mode. This causes #GP during move
from protected mode to real mode when emulator fetches first instruction
after moving to real mode since it uses incorrect CS base and limit to
linearize the %rip. Fix by keeping shadow for SS and CS too.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

rmode_segment_valid() checks if segment descriptor can be used to enter
vm86 mode. VMX spec mandates that in vm86 mode CS register will be of
type data, not code. Lets allow guest entry with vm86 mode if the only
problem with CS register is incorrect type. Otherwise entire real mode
will be emulated.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>

Set segment fields explicitly instead of using  binary operations.

No behaviour changes.
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>