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Merge tag 'kvm-x86-vmx-6.12' of https://github.com/kvm-x86/linux into HEAD

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KVM VMX changes for 6.12:

 - Set FINAL/PAGE in the page fault error code for EPT Violations if and only
   if the GVA is valid.  If the GVA is NOT valid, there is no guest-side page
   table walk and so stuffing paging related metadata is nonsensical.

 - Fix a bug where KVM would incorrectly synthesize a nested VM-Exit instead of
   emulating posted interrupt delivery to L2.

 - Add a lockdep assertion to detect unsafe accesses of vmcs12 structures.

 - Harden eVMCS loading against an impossible NULL pointer deref (really truly
   should be impossible).

 - Minor SGX fix and a cleanup.
This commit is contained in:
Paolo Bonzini
2024-09-14 09:56:06 -04:00
parent 55e6f8f29d f300948251
commit 3f8df62852
13 changed files with 124 additions and 41 deletions
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23
Documentation/virt/kvm/api.rst
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@@ -4214,7 +4214,9 @@ whether or not KVM_CAP_X86_USER_SPACE_MSR's KVM_MSR_EXIT_REASON_FILTER is
enabled. If KVM_MSR_EXIT_REASON_FILTER is enabled, KVM will exit to userspace
on denied accesses, i.e. userspace effectively intercepts the MSR access. If
KVM_MSR_EXIT_REASON_FILTER is not enabled, KVM will inject a #GP into the guest
on denied accesses.
on denied accesses. Note, if an MSR access is denied during emulation of MSR
load/stores during VMX transitions, KVM ignores KVM_MSR_EXIT_REASON_FILTER.
See the below warning for full details.
If an MSR access is allowed by userspace, KVM will emulate and/or virtualize
the access in accordance with the vCPU model. Note, KVM may still ultimately
@@ -4229,9 +4231,22 @@ filtering. In that mode, ``KVM_MSR_FILTER_DEFAULT_DENY`` is invalid and causes
an error.
.. warning::
MSR accesses as part of nested VM-Enter/VM-Exit are not filtered.
This includes both writes to individual VMCS fields and reads/writes
through the MSR lists pointed to by the VMCS.
MSR accesses that are side effects of instruction execution (emulated or
native) are not filtered as hardware does not honor MSR bitmaps outside of
RDMSR and WRMSR, and KVM mimics that behavior when emulating instructions
to avoid pointless divergence from hardware. E.g. RDPID reads MSR_TSC_AUX,
SYSENTER reads the SYSENTER MSRs, etc.
MSRs that are loaded/stored via dedicated VMCS fields are not filtered as
part of VM-Enter/VM-Exit emulation.
MSRs that are loaded/store via VMX's load/store lists _are_ filtered as part
of VM-Enter/VM-Exit emulation. If an MSR access is denied on VM-Enter, KVM
synthesizes a consistency check VM-Exit(EXIT_REASON_MSR_LOAD_FAIL). If an
MSR access is denied on VM-Exit, KVM synthesizes a VM-Abort. In short, KVM
extends Intel's architectural list of MSRs that cannot be loaded/saved via
the VM-Enter/VM-Exit MSR list. It is platform owner's responsibility to
to communicate any such restrictions to their end users.
x2APIC MSR accesses cannot be filtered (KVM silently ignores filters that
cover any x2APIC MSRs).