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Date: Thu, 17 Feb 2022 15:08:29 -0300 From: Leonardo Bras Soares Passos <leobras@...hat.com> To: Paolo Bonzini <pbonzini@...hat.com> Cc: Sean Christopherson <seanjc@...gle.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, "Chang S. Bae" <chang.seok.bae@...el.com>, Andy Lutomirski <luto@...nel.org>, David Gilbert <dgilbert@...hat.com>, Peter Xu <peterx@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 0/2] x86/kvm/fpu: Fix guest migration bugs that can crash guest On Thu, Feb 17, 2022 at 11:52 AM Paolo Bonzini <pbonzini@...hat.com> wrote: > > On 2/17/22 06:30, Leonardo Bras wrote: > > This patchset comes from a bug I found during qemu guest migration from a > > host with newer CPU to a host with an older version of this CPU, and thus > > having less FPU features. > > > > When the guests were created, the one with less features is used as > > config, so migration is possible. > > > > Patch 1 fix a bug that always happens during this migration, and is > > related to the fact that xsave saves all feature flags, but xrstor does > > not touch the PKRU flag. It also changes how fpstate->user_xfeatures > > is set, going from kvm_check_cpuid() to the later called > > kvm_vcpu_after_set_cpuid(). > > > > Patch 2 removes kvm_vcpu_arch.guest_supported_xcr0 since it now > > duplicates guest_fpu.fpstate->user_xfeatures. Some wrappers were > > introduced in order to make it easier to read the replaced version. > > > > Patches were compile-tested, and could fix the bug found. > > Queued, thanks (for 5.17 of course)! For patch 2, I renamed the > function to kvm_guest_supported_xcr0. > > Paolo > That's great! Thanks Paolo!
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