linux-kernel - Re: [PATCH v4 0/4] Relax canonical checks on some arch msrs

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Message-ID: <ZyUrHej3jcZFPXrd@google.com>
Date: Fri, 1 Nov 2024 12:25:17 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: kvm@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Paolo Bonzini <pbonzini@...hat.com>, 
	Ingo Molnar <mingo@...hat.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, linux-kernel@...r.kernel.org, 
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v4 0/4] Relax canonical checks on some arch msrs

On Thu, Oct 31, 2024, Sean Christopherson wrote:
> On Fri, 06 Sep 2024 18:18:20 -0400, Maxim Levitsky wrote:
> > Recently we came up upon a failure where likely the guest writes
> > 0xff4547ceb1600000 to MSR_KERNEL_GS_BASE and later on, qemu
> > sets this value via KVM_PUT_MSRS, and is rejected by the
> > kernel, likely due to not being canonical in 4 level paging.
> > 
> > One of the way to trigger this is to make the guest enter SMM,
> > which causes paging to be disabled, which SMM bios re-enables
> > but not the whole 5 level. MSR_KERNEL_GS_BASE on the other
> > hand continues to contain old value.
> > 
> > [...]
> 
> Applied to kvm-x86 misc, with some massaging (see responsed to individual
> patches).  Thanks!
> 
> [1/4] KVM: x86: drop x86.h include from cpuid.h
>       https://github.com/kvm-x86/linux/commit/391bd0c520c1
> [2/4] KVM: x86: implement emul_is_noncanonical_address using is_noncanonical_address
>       https://github.com/kvm-x86/linux/commit/6c45d62536d0
> [3/4] KVM: x86: model canonical checks more precisely
>       https://github.com/kvm-x86/linux/commit/1b1336d1d858
> [4/4] KVM: nVMX: fix canonical check of vmcs12 HOST_RIP
>       https://github.com/kvm-x86/linux/commit/14a95598b6e7

FYI, I rebased misc to v6.12-rc5, as patches in another series had already been
taken through the tip tree.  New hashes:

[1/5] KVM: x86: drop x86.h include from cpuid.h
      https://github.com/kvm-x86/linux/commit/e52ad1ddd0a3
[2/5] KVM: x86: Route non-canonical checks in emulator through emulate_ops
      https://github.com/kvm-x86/linux/commit/16ccadefa295
[3/5] KVM: x86: Add X86EMUL_F_MSR and X86EMUL_F_DT_LOAD to aid canonical checks
      https://github.com/kvm-x86/linux/commit/c534b37b7584
[4/5] KVM: x86: model canonical checks more precisely
      https://github.com/kvm-x86/linux/commit/9245fd6b8531
[5/5] KVM: nVMX: fix canonical check of vmcs12 HOST_RIP
      https://github.com/kvm-x86/linux/commit/90a877216e6b