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Sat, 08 Nov 2025 23:59:22 -0800 (PST) Received: from [192.168.10.48] ([151.95.110.222]) by smtp.googlemail.com with ESMTPSA id 4fb4d7f45d1cf-6417b28a73esm1229837a12.35.2025.11.08.23.59.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 08 Nov 2025 23:59:21 -0800 (PST) Message-ID: Date: Sun, 9 Nov 2025 08:59:18 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/6] KVM: SVM: Switch svm_copy_lbrs() to a macro To: Yosry Ahmed , Sean Christopherson Cc: Jim Mattson , Maxim Levitsky , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20251108004524.1600006-1-yosry.ahmed@linux.dev> <20251108004524.1600006-5-yosry.ahmed@linux.dev> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <20251108004524.1600006-5-yosry.ahmed@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/8/25 01:45, Yosry Ahmed wrote: > In preparation for using svm_copy_lbrs() with 'struct vmcb_save_area' > without a containing 'struct vmcb', and later even 'struct > vmcb_save_area_cached', make it a macro. Pull the call to > vmcb_mark_dirty() out to the callers. The changes to use `struct vmcb_save_area_cached' are not included in this series, so they are irrelevant. Since I've applied patches 1-3, which fix the worst bugs, there are two ways to handle the rest: * keep the function instead of the macro, while making it take a struct vmcb_save_area (and therefore pulling vmcb_mark_dirty() to the callers and fixing the bug you mention below). * you resubmit with the changes to use struct vmcb_save_area_cached, so that the commit message makes more sense. Thanks, Paolo > Macros are generally not preferred compared to functions, mainly due to > type-safety. However, in this case it seems like having a simple macro > copying a few fields is better than copy-pasting the same 5 lines of > code in different places. > > On the bright side, pulling vmcb_mark_dirty() calls to the callers makes > it clear that in one case, vmcb_mark_dirty() was being called on VMCB12. > It is not architecturally defined for the CPU to clear arbitrary clean > bits, and it is not needed, so drop that one call. > Technically fixes the non-architectural behavior of setting the dirty > bit on VMCB12. > > Fixes: d20c796ca370 ("KVM: x86: nSVM: implement nested LBR virtualization") > Cc: stable@vger.kernel.org > > Signed-off-by: Yosry Ahmed > --- > arch/x86/kvm/svm/nested.c | 16 ++++++++++------ > arch/x86/kvm/svm/svm.c | 11 ----------- > arch/x86/kvm/svm/svm.h | 10 +++++++++- > 3 files changed, 19 insertions(+), 18 deletions(-) > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index c81005b245222..e7861392f2fcd 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -676,10 +676,12 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12 > * Reserved bits of DEBUGCTL are ignored. Be consistent with > * svm_set_msr's definition of reserved bits. > */ > - svm_copy_lbrs(vmcb02, vmcb12); > + svm_copy_lbrs(&vmcb02->save, &vmcb12->save); > + vmcb_mark_dirty(vmcb02, VMCB_LBR); > vmcb02->save.dbgctl &= ~DEBUGCTL_RESERVED_BITS; > } else { > - svm_copy_lbrs(vmcb02, vmcb01); > + svm_copy_lbrs(&vmcb02->save, &vmcb01->save); > + vmcb_mark_dirty(vmcb02, VMCB_LBR); > } > svm_update_lbrv(&svm->vcpu); > } > @@ -1186,10 +1188,12 @@ int nested_svm_vmexit(struct vcpu_svm *svm) > kvm_make_request(KVM_REQ_EVENT, &svm->vcpu); > > if (unlikely(guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV) && > - (svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))) > - svm_copy_lbrs(vmcb12, vmcb02); > - else > - svm_copy_lbrs(vmcb01, vmcb02); > + (svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))) { > + svm_copy_lbrs(&vmcb12->save, &vmcb02->save); > + } else { > + svm_copy_lbrs(&vmcb01->save, &vmcb02->save); > + vmcb_mark_dirty(vmcb01, VMCB_LBR); > + } > > svm_update_lbrv(vcpu); > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index fc42bcdbb5200..9eb112f0e61f0 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -795,17 +795,6 @@ static void svm_recalc_msr_intercepts(struct kvm_vcpu *vcpu) > */ > } > > -void svm_copy_lbrs(struct vmcb *to_vmcb, struct vmcb *from_vmcb) > -{ > - to_vmcb->save.dbgctl = from_vmcb->save.dbgctl; > - to_vmcb->save.br_from = from_vmcb->save.br_from; > - to_vmcb->save.br_to = from_vmcb->save.br_to; > - to_vmcb->save.last_excp_from = from_vmcb->save.last_excp_from; > - to_vmcb->save.last_excp_to = from_vmcb->save.last_excp_to; > - > - vmcb_mark_dirty(to_vmcb, VMCB_LBR); > -} > - > static void __svm_enable_lbrv(struct kvm_vcpu *vcpu) > { > to_svm(vcpu)->vmcb->control.virt_ext |= LBR_CTL_ENABLE_MASK; > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index c2acaa49ee1c5..e510c8183bd87 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -687,8 +687,16 @@ static inline void *svm_vcpu_alloc_msrpm(void) > return svm_alloc_permissions_map(MSRPM_SIZE, GFP_KERNEL_ACCOUNT); > } > > +#define svm_copy_lbrs(to, from) \ > +({ \ > + (to)->dbgctl = (from)->dbgctl; \ > + (to)->br_from = (from)->br_from; \ > + (to)->br_to = (from)->br_to; \ > + (to)->last_excp_from = (from)->last_excp_from; \ > + (to)->last_excp_to = (from)->last_excp_to; \ > +}) > + > void svm_vcpu_free_msrpm(void *msrpm); > -void svm_copy_lbrs(struct vmcb *to_vmcb, struct vmcb *from_vmcb); > void svm_enable_lbrv(struct kvm_vcpu *vcpu); > void svm_update_lbrv(struct kvm_vcpu *vcpu); > Since