kvm_arm_have_ssbd() is now completely unused, get rid of it.
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Signed-off-by: NWill Deacon <will@kernel.org>

The Spectre-v2 mitigation code is pretty unwieldy and hard to maintain.
This is largely due to it being written hastily, without much clue as to
how things would pan out, and also because it ends up mixing policy and
state in such a way that it is very difficult to figure out what's going
on.

Rewrite the Spectre-v2 mitigation so that it clearly separates state from
policy and follows a more structured approach to handling the mitigation.
Signed-off-by: NWill Deacon <will@kernel.org>

The 'flags' field of 'struct mmu_notifier_range' is used to indicate
whether invalidate_range_{start,end}() are permitted to block. In the
case of kvm_mmu_notifier_invalidate_range_start(), this field is not
forwarded on to the architecture-specific implementation of
kvm_unmap_hva_range() and therefore the backend cannot sensibly decide
whether or not to block.

Add an extra 'flags' parameter to kvm_unmap_hva_range() so that
architectures are aware as to whether or not they are permitted to block.

Cc: <stable@vger.kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: James Morse <james.morse@arm.com>
Signed-off-by: NWill Deacon <will@kernel.org>
Message-Id: <20200811102725.7121-2-will@kernel.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

So far, vcpu_has_ptrauth() is implemented in terms of system_supports_*_auth()
calls, which are declared "inline". In some specific conditions (clang
and SCS), the "inline" very much turns into an "out of line", which
leads to a fireworks when this predicate is evaluated on a non-VHE
system (right at the beginning of __hyp_handle_ptrauth).

Instead, make sure vcpu_has_ptrauth gets expanded inline by directly
using the cpus_have_final_cap() helpers, which are __always_inline,
generate much better code, and are the only thing that make sense when
running at EL2 on a nVHE system.

Fixes: 29eb5a3c ("KVM: arm64: Handle PtrAuth traps early")
Reported-by: NNathan Chancellor <natechancellor@gmail.com>
Reported-by: NNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Tested-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Link: https://lore.kernel.org/r/20200722162231.3689767-1-maz@kernel.org

In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
structure. For historical reasons, many kvm-related function parameters
retain the 'kvm_run' and 'kvm_vcpu' parameters at the same time. This
patch does a unified cleanup of these remaining redundant parameters.
Signed-off-by: NTianjia Zhang <tianjia.zhang@linux.alibaba.com>
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200623131418.31473-3-tianjia.zhang@linux.alibaba.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move to the common MMU memory cache implementation now that the common
code and arm64's existing code are semantically compatible.

No functional change intended.

Cc: Marc Zyngier <maz@kernel.org>
Suggested-by: NChristoffer Dall <christoffer.dall@arm.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200703023545.8771-19-sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add a "gfp_zero" member to arm64's 'struct kvm_mmu_memory_cache' to make
the struct and its usage compatible with the common 'struct
kvm_mmu_memory_cache' in linux/kvm_host.h.  This will minimize code
churn when arm64 moves to the common implementation in a future patch, at
the cost of temporarily having somewhat silly code.

Note, GFP_PGTABLE_USER is equivalent to GFP_KERNEL_ACCOUNT | GFP_ZERO:

  #define GFP_PGTABLE_USER  (GFP_PGTABLE_KERNEL | __GFP_ACCOUNT)
  |
  -> #define GFP_PGTABLE_KERNEL        (GFP_KERNEL | __GFP_ZERO)

  == GFP_KERNEL | __GFP_ACCOUNT | __GFP_ZERO

versus

  #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT)

    with __GFP_ZERO explicitly OR'd in

  == GFP_KERNEL | __GFP_ACCOUNT | __GFP_ZERO

No functional change intended.
Tested-by: NMarc Zyngier <maz@kernel.org>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200703023545.8771-18-sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move the timer gsisters to the sysreg file. This will further help when
they are directly changed by a nesting hypervisor in the VNCR page.

This requires moving the initialisation of the timer struct so that some
of the helpers (such as arch_timer_ctx_index) can work correctly at an
early stage.
Signed-off-by: NMarc Zyngier <maz@kernel.org>

SPSR_EL1 being a VNCR-capable register with ARMv8.4-NV, move it to
the sysregs array and update the accessors.
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

As we're about to move SPSR_EL1 into the VNCR page, we need to
disassociate it from the rest of the 32bit cruft. Let's break
the array into individual fields.
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

SP_EL1 being a VNCR-capable register with ARMv8.4-NV, move it to the
system register array and update the accessors.
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

As ELR-EL1 is a VNCR-capable register with ARMv8.4-NV, let's move it to
the sys_regs array and repaint the accessors. While we're at it, let's
kill the now useless accessors used only on the fault injection path.
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

struct kvm_regs is used by userspace to indicate which register gets
accessed by the {GET,SET}_ONE_REG API. But as we're about to refactor
the layout of the in-kernel register structures, we need the kernel to
move away from it.

Let's make kvm_regs userspace only, and let the kernel map it to its own
internal representation.
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

Switch the hypervisor code to using ctxt_sys_reg/__vcpu_sys_reg instead
of raw sys_regs accesses. No intended functionnal change.
Signed-off-by: NMarc Zyngier <maz@kernel.org>

In order to allow the disintegration of the per-vcpu sysreg array,
let's introduce a new helper (ctxt_sys_reg()) that returns the
in-memory copy of a system register, picked from a given context.

__vcpu_sys_reg() is rewritten to use this helper.
Signed-off-by: NMarc Zyngier <maz@kernel.org>

As we are about to reuse our stage 2 page table manipulation code for
shadow stage 2 page tables in the context of nested virtualization, we
are going to manage multiple stage 2 page tables for a single VM.

This requires some pretty invasive changes to our data structures,
which moves the vmid and pgd pointers into a separate structure and
change pretty much all of our mmu code to operate on this structure
instead.

The new structure is called struct kvm_s2_mmu.

There is no intended functional change by this patch alone.
Reviewed-by: NJames Morse <james.morse@arm.com>
Reviewed-by: NAlexandru Elisei <alexandru.elisei@arm.com>
[Designed data structure layout in collaboration]
Signed-off-by: NChristoffer Dall <christoffer.dall@arm.com>
Co-developed-by: NMarc Zyngier <maz@kernel.org>
[maz: Moved the last_vcpu_ran down to the S2 MMU structure as well]
Signed-off-by: NMarc Zyngier <maz@kernel.org>

sysreg-sr.c contains KVM's code for saving/restoring system registers, with
some code shared between VHE/nVHE. These common routines are moved to
a header file, VHE-specific code is moved to vhe/sysreg-sr.c and nVHE-specific
code to nvhe/sysreg-sr.c.
Signed-off-by: NDavid Brazdil <dbrazdil@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200625131420.71444-12-dbrazdil@google.com

Once hyp functions are moved to a hyp object, they will have prefixed symbols.
This change declares and gets the address of the prefixed version for calls to
the hyp functions.

To aid migration, the hyp functions that have not yet moved have their prefixed
versions aliased to their non-prefixed version. This begins with all the hyp
functions being listed and will reduce to none of them once the migration is
complete.
Signed-off-by: NAndrew Scull <ascull@google.com>

[David: Extracted kvm_call_hyp nVHE branches into own helper macros, added
        comments around symbol aliases.]
Signed-off-by: NDavid Brazdil <dbrazdil@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200625131420.71444-6-dbrazdil@google.com

AArch32 CP1x registers are overlayed on their AArch64 counterparts
in the vcpu struct. This leads to an interesting problem as they
are stored in their CPU-local format, and thus a CP1x register
doesn't "hit" the lower 32bit portion of the AArch64 register on
a BE host.

To workaround this unfortunate situation, introduce a bias trick
in the vcpu_cp1x() accessors which picks the correct half of the
64bit register.

Cc: stable@vger.kernel.org
Reported-by: NJames Morse <james.morse@arm.com>
Tested-by: NJames Morse <james.morse@arm.com>
Acked-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

For very long, we have kept this pointer back to the per-cpu
host state, despite having working per-cpu accessors at EL2
for some time now.

Recent investigations have shown that this pointer is easy
to abuse in preemptible context, which is a sure sign that
it would better be gone. Not to mention that a per-cpu
pointer is faster to access at all times.
Reported-by: NAndrew Scull <ascull@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com
Reviewed-by: NAndrew Scull <ascull@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

With ARMv8.5-GTG, the hardware (or more likely a hypervisor) can
advertise the supported Stage-2 page sizes.

Let's check this at boot time.
Reviewed-by: NSuzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: NAlexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Signed-off-by: NWill Deacon <will@kernel.org>

The general comment about keeping the enum order in sync
with the save/restore code has been obsolete for many years now.

Just drop it.

Note that there are other ordering requirements in the enum,
such as the PtrAuth and PMU registers, which are still valid.
Reported-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

Pull bits of code to the only place where it is used. Remove empty function
__cpu_init_stage2(). Remove redundant has_vhe() check since this function is
nVHE-only. No functional changes intended.
Signed-off-by: NDavid Brazdil <dbrazdil@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200515152056.83158-1-dbrazdil@google.com

There is already support of enabling dirty log gradually in small chunks
for x86 in commit 3c9bd400 ("KVM: x86: enable dirty log gradually in
small chunks"). This adds support for arm64.

x86 still writes protect all huge pages when DIRTY_LOG_INITIALLY_ALL_SET
is enabled. However, for arm64, both huge pages and normal pages can be
write protected gradually by userspace.

Under the Huawei Kunpeng 920 2.6GHz platform, I did some tests on 128G
Linux VMs with different page size. The memory pressure is 127G in each
case. The time taken of memory_global_dirty_log_start in QEMU is listed
below:

Page Size      Before    After Optimization
  4K            650ms         1.8ms
  2M             4ms          1.8ms
  1G             2ms          1.8ms

Besides the time reduction, the biggest improvement is that we will minimize
the performance side effect (because of dissolving huge pages and marking
memslots dirty) on guest after enabling dirty log.
Signed-off-by: NKeqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200413122023.52583-1-zhukeqian1@huawei.com

Two new stats for exposing halt-polling cpu usage:
halt_poll_success_ns
halt_poll_fail_ns

Thus sum of these 2 stats is the total cpu time spent polling. "success"
means the VCPU polled until a virtual interrupt was delivered. "fail"
means the VCPU had to schedule out (either because the maximum poll time
was reached or it needed to yield the CPU).

To avoid touching every arch's kvm_vcpu_stat struct, only update and
export halt-polling cpu usage stats if we're on x86.

Exporting cpu usage as a u64 and in nanoseconds means we will overflow at
~500 years, which seems reasonably large.
Signed-off-by: NDavid Matlack <dmatlack@google.com>
Signed-off-by: NJon Cargille <jcargill@google.com>
Reviewed-by: NJim Mattson <jmattson@google.com>

Message-Id: <20200508182240.68440-1-jcargill@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Errata 1165522, 1319367 and 1530923 each allow TLB entries to be
allocated as a result of a speculative AT instruction. In order to
avoid mandating VHE on certain affected CPUs, apply the workaround to
both the nVHE and the VHE case for all affected CPUs.
Signed-off-by: NAndrew Scull <ascull@google.com>
Acked-by: NWill Deacon <will@kernel.org>
CC: Marc Zyngier <maz@kernel.org>
CC: James Morse <james.morse@arm.com>
CC: Suzuki K Poulose <suzuki.poulose@arm.com>
CC: Will Deacon <will@kernel.org>
CC: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20200504094858.108917-1-ascull@google.comSigned-off-by: NWill Deacon <will@kernel.org>

Each time a Group-enable bit gets flipped, the state of these bits
needs to be forwarded to the hardware. This is a pretty heavy
handed operation, requiring all vcpus to reload their GICv4
configuration. It is thus implemented as a new request type.

These enable bits are programmed into the HW by setting the VGrp{0,1}En
fields of GICR_VPENDBASER when the vPEs are made resident again.

Of course, we only support Group-1 for now...
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Reviewed-by: NZenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20200304203330.4967-22-maz@kernel.org

With VHE, running a vCPU always requires the sequence:

1. kvm_arm_vhe_guest_enter();
2. kvm_vcpu_run_vhe();
3. kvm_arm_vhe_guest_exit()

... and as we invoke this from the shared arm/arm64 KVM code, 32-bit arm
has to provide stubs for all three functions.

To simplify the common code, and make it easier to make further
modifications to the arm64-specific portions in the near future, let's
fold kvm_arm_vhe_guest_enter() and kvm_arm_vhe_guest_exit() into
kvm_vcpu_run_vhe().

The 32-bit stubs for kvm_arm_vhe_guest_enter() and
kvm_arm_vhe_guest_exit() are removed, as they are no longer used. The
32-bit stub for kvm_vcpu_run_vhe() is left as-is.

There should be no functional change as a result of this patch.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200210114757.2889-1-mark.rutland@arm.com

For ring-based dirty log tracking, it will be more efficient to account
writes during schedule-out or schedule-in to the currently running VCPU.
We would like to do it even if the write doesn't use the current VCPU's
address space, as is the case for cached writes (see commit 4e335d9e,
"Revert "KVM: Support vCPU-based gfn->hva cache"", 2017-05-02).

Therefore, add a mechanism to track the currently-loaded kvm_vcpu struct.
There is already something similar in KVM/ARM; one important difference
is that kvm_arch_vcpu_{load,put} have two callers in virt/kvm/kvm_main.c:
we have to update both the architecture-independent vcpu_{load,put} and
the preempt notifiers.

Another change made in the process is to allow using kvm_get_running_vcpu()
in preemptible code.  This is allowed because preempt notifiers ensure
that the value does not change even after the VCPU thread is migrated.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Remove kvm_arch_vcpu_init() and kvm_arch_vcpu_uninit() now that all
arch specific implementations are nops.
Acked-by: NChristoffer Dall <christoffer.dall@arm.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add an arm specific hook to free the arm64-only sve_state.  Doing so
eliminates the last functional code from kvm_arch_vcpu_uninit() across
all architectures and paves the way for removing kvm_arch_vcpu_init()
and kvm_arch_vcpu_uninit() entirely.
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Our MMIO handling is a bit odd, in the sense that it uses an
intermediate per-vcpu structure to store the various decoded
information that describe the access.

But the same information is readily available in the HSR/ESR_EL2
field, and we actually use this field to populate the structure.

Let's simplify the whole thing by getting rid of the superfluous
structure and save a (tiny) bit of space in the vcpu structure.

[32bit fix courtesy of Olof Johansson <olof@lixom.net>]
Signed-off-by: NMarc Zyngier <maz@kernel.org>

Cortex-A55 is affected by a similar erratum, so rename the existing
workaround for errarum 1165522 so it can be used for both errata.
Acked-by: NMarc Zyngier <maz@kernel.org>
Reviewed-by: NSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: NSteven Price <steven.price@arm.com>
Signed-off-by: NWill Deacon <will@kernel.org>

We finalize the system wide capabilities after the SMP CPUs
are booted by the kernel. This is used as a marker for deciding
various checks in the kernel. e.g, sanity check the hotplugged
CPUs for missing mandatory features.

However there is no explicit helper available for this in the
kernel. There is sys_caps_initialised, which is not exposed.
The other closest one we have is the jump_label arm64_const_caps_ready
which denotes that the capabilities are set and the capability checks
could use the individual jump_labels for fast path. This is
performed before setting the ELF Hwcaps, which must be checked
against the new CPUs. We also perform some of the other initialization
e.g, SVE setup, which is important for the use of FP/SIMD
where SVE is supported. Normally userspace doesn't get to run
before we finish this. However the in-kernel users may
potentially start using the neon mode. So, we need to
reject uses of neon mode before we are set. Instead of defining
a new marker for the completion of SVE setup, we could simply
reuse the arm64_const_caps_ready and enable it once we have
finished all the setup. Also we could expose this to the
various users as "system_capabilities_finalized()" to make
it more meaningful than "const_caps_ready".

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: NArd Biesheuvel <ardb@kernel.org>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: NWill Deacon <will@kernel.org>

Allow user space to inform the KVM host where in the physical memory
map the paravirtualized time structures should be located.

User space can set an attribute on the VCPU providing the IPA base
address of the stolen time structure for that VCPU. This must be
repeated for every VCPU in the VM.

The address is given in terms of the physical address visible to
the guest and must be 64 byte aligned. The guest will discover the
address via a hypercall.
Signed-off-by: NSteven Price <steven.price@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

Implement the service call for configuring a shared structure between a
VCPU and the hypervisor in which the hypervisor can write the time
stolen from the VCPU's execution time by other tasks on the host.

User space allocates memory which is placed at an IPA also chosen by user
space. The hypervisor then updates the shared structure using
kvm_put_guest() to ensure single copy atomicity of the 64-bit value
reporting the stolen time in nanoseconds.

Whenever stolen time is enabled by the guest, the stolen time counter is
reset.

The stolen time itself is retrieved from the sched_info structure
maintained by the Linux scheduler code. We enable SCHEDSTATS when
selecting KVM Kconfig to ensure this value is meaningful.
Signed-off-by: NSteven Price <steven.price@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

This provides a mechanism for querying which paravirtualized time
features are available in this hypervisor.

Also add the header file which defines the ABI for the paravirtualized
time features we're about to add.
Signed-off-by: NSteven Price <steven.price@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

For a long time, if a guest accessed memory outside of a memslot using
any of the load/store instructions in the architecture which doesn't
supply decoding information in the ESR_EL2 (the ISV bit is not set), the
kernel would print the following message and terminate the VM as a
result of returning -ENOSYS to userspace:

  load/store instruction decoding not implemented

The reason behind this message is that KVM assumes that all accesses
outside a memslot is an MMIO access which should be handled by
userspace, and we originally expected to eventually implement some sort
of decoding of load/store instructions where the ISV bit was not set.

However, it turns out that many of the instructions which don't provide
decoding information on abort are not safe to use for MMIO accesses, and
the remaining few that would potentially make sense to use on MMIO
accesses, such as those with register writeback, are not used in
practice.  It also turns out that fetching an instruction from guest
memory can be a pretty horrible affair, involving stopping all CPUs on
SMP systems, handling multiple corner cases of address translation in
software, and more.  It doesn't appear likely that we'll ever implement
this in the kernel.

What is much more common is that a user has misconfigured his/her guest
and is actually not accessing an MMIO region, but just hitting some
random hole in the IPA space.  In this scenario, the error message above
is almost misleading and has led to a great deal of confusion over the
years.

It is, nevertheless, ABI to userspace, and we therefore need to
introduce a new capability that userspace explicitly enables to change
behavior.

This patch introduces KVM_CAP_ARM_NISV_TO_USER (NISV meaning Non-ISV)
which does exactly that, and introduces a new exit reason to report the
event to userspace.  User space can then emulate an exception to the
guest, restart the guest, suspend the guest, or take any other
appropriate action as per the policy of the running system.
Reported-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: NChristoffer Dall <christoffer.dall@arm.com>
Reviewed-by: NAlexander Graf <graf@amazon.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>

The GICv3 architecture specification is incredibly misleading when it
comes to PMR and the requirement for a DSB. It turns out that this DSB
is only required if the CPU interface sends an Upstream Control
message to the redistributor in order to update the RD's view of PMR.

This message is only sent when ICC_CTLR_EL1.PMHE is set, which isn't
the case in Linux. It can still be set from EL3, so some special care
is required. But the upshot is that in the (hopefuly large) majority
of the cases, we can drop the DSB altogether.

This relies on a new static key being set if the boot CPU has PMHE
set. The drawback is that this static key has to be exported to
modules.

Cc: Will Deacon <will@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

As part of setting up the host context, we populate its
MPIDR by using cpu_logical_map(). It turns out that contrary
to arm64, cpu_logical_map() on 32bit ARM doesn't return the
*full* MPIDR, but a truncated version.

This leaves the host MPIDR slightly corrupted after the first
run of a VM, since we won't correctly restore the MPIDR on
exit. Oops.

Since we cannot trust cpu_logical_map(), let's adopt a different
strategy. We move the initialization of the host CPU context as
part of the per-CPU initialization (which, in retrospect, makes
a lot of sense), and directly read the MPIDR from the HW. This
is guaranteed to work on both arm and arm64.
Reported-by: NAndre Przywara <Andre.Przywara@arm.com>
Tested-by: NAndre Przywara <Andre.Przywara@arm.com>
Fixes: 32f13955 ("arm/arm64: KVM: Statically configure the host's view of MPIDR")
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>