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KVM x86 misc changes for 6.19:

Browse source 
- Fix an async #PF bug where KVM would clear the completion queue when the
    guest transitioned in and out of paging mode, e.g. when handling an SMI and
    then returning to paged mode via RSM.
 
  - Fix a bug where TDX would effectively corrupt user-return MSR values if the
    TDX Module rejects VP.ENTER and thus doesn't clobber host MSRs as expected.
 
  - Leave the user-return notifier used to restore MSRs registered when
    disabling virtualization, and instead pin kvm.ko.  Restoring host MSRs via
    IPI callback is either pointless (clean reboot) or dangerous (forced reboot)
    since KVM has no idea what code it's interrupting.
 
  - Use the checked version of {get,put}_user(), as Linus wants to kill them
    off, and they're measurably faster on modern CPUs due to the unchecked
    versions containing an LFENCE.
 
  - Fix a long-lurking bug where KVM's lack of catch-up logic for periodic APIC
    timers can result in a hard lockup in the host.
 
  - Revert the periodic kvmclock sync logic now that KVM doesn't use a
    clocksource that's subject to NPT corrections.
 
  - Clean up KVM's handling of MMIO Stale Data and L1TF, and bury the latter
    behind CONFIG_CPU_MITIGATIONS.
 
  - Context switch XCR0, XSS, and PKRU outside of the entry/exit fastpath as
    the only reason they were handled in the faspath was to paper of a bug in
    the core #MC code that has long since been fixed.
 
  - Add emulator support for AVX MOV instructions to play nice with emulated
    devices whose PCI BARs guest drivers like to access with large multi-byte
    instructions.
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Merge tag 'kvm-x86-misc-6.19' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.19:

 - Fix an async #PF bug where KVM would clear the completion queue when the
   guest transitioned in and out of paging mode, e.g. when handling an SMI and
   then returning to paged mode via RSM.

 - Fix a bug where TDX would effectively corrupt user-return MSR values if the
   TDX Module rejects VP.ENTER and thus doesn't clobber host MSRs as expected.

 - Leave the user-return notifier used to restore MSRs registered when
   disabling virtualization, and instead pin kvm.ko.  Restoring host MSRs via
   IPI callback is either pointless (clean reboot) or dangerous (forced reboot)
   since KVM has no idea what code it's interrupting.

 - Use the checked version of {get,put}_user(), as Linus wants to kill them
   off, and they're measurably faster on modern CPUs due to the unchecked
   versions containing an LFENCE.

 - Fix a long-lurking bug where KVM's lack of catch-up logic for periodic APIC
   timers can result in a hard lockup in the host.

 - Revert the periodic kvmclock sync logic now that KVM doesn't use a
   clocksource that's subject to NPT corrections.

 - Clean up KVM's handling of MMIO Stale Data and L1TF, and bury the latter
   behind CONFIG_CPU_MITIGATIONS.

 - Context switch XCR0, XSS, and PKRU outside of the entry/exit fastpath as
   the only reason they were handled in the faspath was to paper of a bug in
   the core #MC code that has long since been fixed.

 - Add emulator support for AVX MOV instructions to play nice with emulated
   devices whose PCI BARs guest drivers like to access with large multi-byte
   instructions.
This commit is contained in:
Paolo Bonzini 2025-11-26 09:34:21 +01:00
commit e64dcfab57
24 changed files with 703 additions and 497 deletions
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