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Wed, 04 Jun 2025 08:35:42 -0700 (PDT) Received: from [192.168.10.81] ([151.49.64.79]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-3a4efe6ca46sm22536035f8f.31.2025.06.04.08.35.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Jun 2025 08:35:42 -0700 (PDT) Message-ID: Date: Wed, 4 Jun 2025 17:35:41 +0200 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 08/28] KVM: nSVM: Use dedicated array of MSRPM offsets to merge L0 and L1 bitmaps To: Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , Xin Li , Chao Gao , Dapeng Mi References: <20250529234013.3826933-1-seanjc@google.com> <20250529234013.3826933-9-seanjc@google.com> 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: <20250529234013.3826933-9-seanjc@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/30/25 01:39, Sean Christopherson wrote: > Use a dedicated array of MSRPM offsets to merge L0 and L1 bitmaps, i.e. to > merge KVM's vmcb01 bitmap with L1's vmcb12 bitmap. This will eventually > allow for the removal of direct_access_msrs, as the only path where > tracking the offsets is truly justified is the merge for nested SVM, where > merging in chunks is an easy way to batch uaccess reads/writes. > > Opportunistically omit the x2APIC MSRs from the merge-specific array > instead of filtering them out at runtime. > > Note, disabling interception of XSS, EFER, PAT, GHCB, and TSC_AUX is > mutually exclusive with nested virtualization, as KVM passes through the > MSRs only for SEV-ES guests, and KVM doesn't support nested virtualization > for SEV+ guests. Defer removing those MSRs to a future cleanup in order > to make this refactoring as benign as possible. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/svm/nested.c | 72 +++++++++++++++++++++++++++++++++------ > arch/x86/kvm/svm/svm.c | 4 +++ > arch/x86/kvm/svm/svm.h | 2 ++ > 3 files changed, 67 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index 89a77f0f1cc8..e53020939e60 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -184,6 +184,64 @@ void recalc_intercepts(struct vcpu_svm *svm) > } > } > > +static int nested_svm_msrpm_merge_offsets[9] __ro_after_init; > +static int nested_svm_nr_msrpm_merge_offsets __ro_after_init; > + > +int __init nested_svm_init_msrpm_merge_offsets(void) > +{ > + const u32 merge_msrs[] = { "static const", please. Paolo > + MSR_STAR, > + MSR_IA32_SYSENTER_CS, > + MSR_IA32_SYSENTER_EIP, > + MSR_IA32_SYSENTER_ESP, > + #ifdef CONFIG_X86_64 > + MSR_GS_BASE, > + MSR_FS_BASE, > + MSR_KERNEL_GS_BASE, > + MSR_LSTAR, > + MSR_CSTAR, > + MSR_SYSCALL_MASK, > + #endif > + MSR_IA32_SPEC_CTRL, > + MSR_IA32_PRED_CMD, > + MSR_IA32_FLUSH_CMD, > + MSR_IA32_LASTBRANCHFROMIP, > + MSR_IA32_LASTBRANCHTOIP, > + MSR_IA32_LASTINTFROMIP, > + MSR_IA32_LASTINTTOIP, > + > + MSR_IA32_XSS, > + MSR_EFER, > + MSR_IA32_CR_PAT, > + MSR_AMD64_SEV_ES_GHCB, > + MSR_TSC_AUX, > + }; > + int i, j; > + > + for (i = 0; i < ARRAY_SIZE(merge_msrs); i++) { > + u32 offset = svm_msrpm_offset(merge_msrs[i]); > + > + if (WARN_ON(offset == MSR_INVALID)) > + return -EIO; > + > + for (j = 0; j < nested_svm_nr_msrpm_merge_offsets; j++) { > + if (nested_svm_msrpm_merge_offsets[j] == offset) > + break; > + } > + > + if (j < nested_svm_nr_msrpm_merge_offsets) > + continue; > + > + if (WARN_ON(j >= ARRAY_SIZE(nested_svm_msrpm_merge_offsets))) > + return -EIO; > + > + nested_svm_msrpm_merge_offsets[j] = offset; > + nested_svm_nr_msrpm_merge_offsets++; > + } > + > + return 0; > +} > + > /* > * Merge L0's (KVM) and L1's (Nested VMCB) MSR permission bitmaps. The function > * is optimized in that it only merges the parts where KVM MSR permission bitmap > @@ -216,19 +274,11 @@ static bool nested_svm_merge_msrpm(struct kvm_vcpu *vcpu) > if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) > return true; > > - for (i = 0; i < MSRPM_OFFSETS; i++) { > - u32 value, p; > + for (i = 0; i < nested_svm_nr_msrpm_merge_offsets; i++) { > + const int p = nested_svm_msrpm_merge_offsets[i]; > + u32 value; > u64 offset; > > - if (msrpm_offsets[i] == 0xffffffff) > - break; > - > - p = msrpm_offsets[i]; > - > - /* x2apic msrs are intercepted always for the nested guest */ > - if (is_x2apic_msrpm_offset(p)) > - continue; > - > offset = svm->nested.ctl.msrpm_base_pa + (p * 4); > > if (kvm_vcpu_read_guest(vcpu, offset, &value, 4)) > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 1c70293400bc..84dd1f220986 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -5689,6 +5689,10 @@ static int __init svm_init(void) > if (!kvm_is_svm_supported()) > return -EOPNOTSUPP; > > + r = nested_svm_init_msrpm_merge_offsets(); > + if (r) > + return r; > + > r = kvm_x86_vendor_init(&svm_init_ops); > if (r) > return r; > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index 909b9af6b3c1..0a8041d70994 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -686,6 +686,8 @@ static inline bool nested_exit_on_nmi(struct vcpu_svm *svm) > return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_NMI); > } > > +int __init nested_svm_init_msrpm_merge_offsets(void); > + > int enter_svm_guest_mode(struct kvm_vcpu *vcpu, > u64 vmcb_gpa, struct vmcb *vmcb12, bool from_vmrun); > void svm_leave_nested(struct kvm_vcpu *vcpu);