linux-kernel - Re: [GIT PULL] KVM: x86: VMX changes for 6.19

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Message-ID: <CABgObfbvYC9mGL8x1JSQwmq7BT9j7gwf11nmHsumOumd4P0abg@mail.gmail.com>
Date: Wed, 26 Nov 2025 09:50:04 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] KVM: x86: VMX changes for 6.19

On Wed, Nov 26, 2025 at 2:45 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> The highlight is EPTP construction cleanup that's worthwhile on its own, but
> is also a step toward eliding the EPT flushes that KVM does on pCPU migration,
> which are especially costly when running nested:
>
> https://lore.kernel.org/all/aJKW9gTeyh0-pvcg@google.com
>
> The following changes since commit 3a8660878839faadb4f1a6dd72c3179c1df56787:
>
>   Linux 6.18-rc1 (2025-10-12 13:42:36 -0700)
>
> are available in the Git repository at:
>
>   https://github.com/kvm-x86/linux.git tags/kvm-x86-vmx-6.19
>
> for you to fetch changes up to dfd1572a64c90770a2bddfab9bbb69932217b1da:
>
>   KVM: VMX: Make loaded_vmcs_clear() static in vmx.c (2025-11-11 07:41:16 -0800)

Pulled; there was another minor conflict due to the introduction of
kvm_request_l1tf_flush_l1d().

Paolo

> ----------------------------------------------------------------
> KVM VMX changes for 6.19:
>
>  - Use the root role from kvm_mmu_page to construct EPTPs instead of the
>    current vCPU state, partly as worthwhile cleanup, but mostly to pave the
>    way for tracking per-root TLB flushes so that KVM can elide EPT flushes on
>    pCPU migration if KVM has flushed the root at least once.
>
>  - Add a few missing nested consistency checks.
>
>  - Rip out support for doing "early" consistency checks via hardware as the
>    functionality hasn't been used in years and is no longer useful in general,
>    and replace it with an off-by-default module param to detected missed
>    consistency checks (i.e. WARN if hardware finds a check that KVM does not).
>
>  - Fix a currently-benign bug where KVM would drop the guest's SPEC_CTRL[63:32]
>    on VM-Enter.
>
>  - Misc cleanups.
>
> ----------------------------------------------------------------
> Dmytro Maluka (1):
>       KVM: VMX: Remove stale vmx_set_dr6() declaration
>
> Sean Christopherson (10):
>       KVM: VMX: Hoist construct_eptp() "up" in vmx.c
>       KVM: nVMX: Hardcode dummy EPTP used for early nested consistency checks
>       KVM: x86/mmu: Move "dummy root" helpers to spte.h
>       KVM: VMX: Use kvm_mmu_page role to construct EPTP, not current vCPU state
>       KVM: nVMX: Add consistency check for TPR_THRESHOLD[31:4]!=0 without VID
>       KVM: nVMX: Add consistency check for TSC_MULTIPLIER=0
>       KVM: nVMX: Stuff vmcs02.TSC_MULTIPLIER early on for nested early checks
>       KVM: nVMX: Remove support for "early" consistency checks via hardware
>       KVM: nVMX: Add an off-by-default module param to WARN on missed consistency checks
>       KVM: VMX: Make loaded_vmcs_clear() static in vmx.c
>
> Thorsten Blum (1):
>       KVM: TDX: Replace kmalloc + copy_from_user with memdup_user in tdx_td_init()
>
> Uros Bizjak (1):
>       KVM: VMX: Ensure guest's SPEC_CTRL[63:32] is loaded on VM-Enter
>
> Xin Li (1):
>       KVM: nVMX: Use vcpu instead of vmx->vcpu when vcpu is available
>
>  arch/x86/kvm/mmu/mmu_internal.h |  10 ---
>  arch/x86/kvm/mmu/spte.h         |  10 +++
>  arch/x86/kvm/vmx/nested.c       | 173 ++++++++++++++--------------------------
>  arch/x86/kvm/vmx/tdx.c          |  30 +++----
>  arch/x86/kvm/vmx/vmenter.S      |  20 +++--
>  arch/x86/kvm/vmx/vmx.c          |  59 +++++++++-----
>  arch/x86/kvm/vmx/vmx.h          |   2 -
>  arch/x86/kvm/vmx/x86_ops.h      |   1 -
>  8 files changed, 135 insertions(+), 170 deletions(-)
>