* [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest @ 2020-07-08 9:36 Vitaly Kuznetsov 2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov ` (2 more replies) 0 siblings, 3 replies; 7+ messages in thread From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw) To: kvm, Paolo Bonzini Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid, linux-kernel This is a succesor of "[PATCH] KVM: x86: drop erroneous mmu_check_root() from fast_pgd_switch()". Undesired triple fault gets injected to L1 guest on SVM when L2 is launched with certain CR3 values. #TF is raised by mmu_check_root() check in fast_pgd_switch() and the root cause is that when kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT enabled CR3 points to a nGPA so we can't check it with kvm_is_visible_gfn(). Fix the issue by moving kvm_mmu_new_pgd() to the right place when switching to nested guest and drop the unneeded mmu_check_root() check from fast_pgd_switch(). Vitaly Kuznetsov (3): KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() arch/x86/include/asm/kvm_host.h | 7 ++++++- arch/x86/kvm/mmu.h | 3 ++- arch/x86/kvm/mmu/mmu.c | 36 ++++++++++++++++++++++++--------- arch/x86/kvm/svm/nested.c | 5 +++-- arch/x86/kvm/x86.c | 8 +++++--- 5 files changed, 43 insertions(+), 16 deletions(-) -- 2.25.4 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() 2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov @ 2020-07-08 9:36 ` Vitaly Kuznetsov 2020-07-08 11:25 ` Paolo Bonzini 2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov 2020-07-08 9:36 ` [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov 2 siblings, 1 reply; 7+ messages in thread From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw) To: kvm, Paolo Bonzini Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid, linux-kernel As a preparatory change for moving kvm_mmu_new_pgd() from nested_prepare_vmcb_save() to nested_svm_init_mmu_context() split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu(). This also makes the code look more like nVMX (kvm_init_shadow_ept_mmu()). No functional change intended. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> --- arch/x86/kvm/mmu.h | 3 ++- arch/x86/kvm/mmu/mmu.c | 31 ++++++++++++++++++++++++------- arch/x86/kvm/svm/nested.c | 3 ++- 3 files changed, 28 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 444bb9c54548..94378ef1df54 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -57,7 +57,8 @@ void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context); void kvm_init_mmu(struct kvm_vcpu *vcpu, bool reset_roots); -void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer); +void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer, + gpa_t nested_cr3); void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly, bool accessed_dirty, gpa_t new_eptp); bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu); diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 76817d13c86e..167d12ab957a 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4952,14 +4952,10 @@ kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only) return role; } -void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer) +static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, + u32 efer, union kvm_mmu_role new_role) { struct kvm_mmu *context = vcpu->arch.mmu; - union kvm_mmu_role new_role = - kvm_calc_shadow_mmu_root_page_role(vcpu, false); - - if (new_role.as_u64 == context->mmu_role.as_u64) - return; if (!(cr0 & X86_CR0_PG)) nonpaging_init_context(vcpu, context); @@ -4973,7 +4969,28 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer) context->mmu_role.as_u64 = new_role.as_u64; reset_shadow_zero_bits_mask(vcpu, context); } -EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu); + +static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer) +{ + struct kvm_mmu *context = vcpu->arch.mmu; + union kvm_mmu_role new_role = + kvm_calc_shadow_mmu_root_page_role(vcpu, false); + + if (new_role.as_u64 != context->mmu_role.as_u64) + shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role); +} + +void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer, + gpa_t nested_cr3) +{ + struct kvm_mmu *context = vcpu->arch.mmu; + union kvm_mmu_role new_role = + kvm_calc_shadow_mmu_root_page_role(vcpu, false); + + if (new_role.as_u64 != context->mmu_role.as_u64) + shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role); +} +EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu); static union kvm_mmu_role kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty, diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 6bceafb19108..e424bce13e6c 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -87,7 +87,8 @@ static void nested_svm_init_mmu_context(struct kvm_vcpu *vcpu) WARN_ON(mmu_is_nested(vcpu)); vcpu->arch.mmu = &vcpu->arch.guest_mmu; - kvm_init_shadow_mmu(vcpu, X86_CR0_PG, hsave->save.cr4, hsave->save.efer); + kvm_init_shadow_npt_mmu(vcpu, X86_CR0_PG, hsave->save.cr4, hsave->save.efer, + svm->nested.ctl.nested_cr3); vcpu->arch.mmu->get_guest_pgd = nested_svm_get_tdp_cr3; vcpu->arch.mmu->get_pdptr = nested_svm_get_tdp_pdptr; vcpu->arch.mmu->inject_page_fault = nested_svm_inject_npf_exit; -- 2.25.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() 2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov @ 2020-07-08 11:25 ` Paolo Bonzini 0 siblings, 0 replies; 7+ messages in thread From: Paolo Bonzini @ 2020-07-08 11:25 UTC (permalink / raw) To: Vitaly Kuznetsov, kvm Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid, linux-kernel On 08/07/20 11:36, Vitaly Kuznetsov wrote: > @@ -4973,7 +4969,28 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer) > context->mmu_role.as_u64 = new_role.as_u64; > reset_shadow_zero_bits_mask(vcpu, context); > } > -EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu); > + > +static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer) > +{ > + struct kvm_mmu *context = vcpu->arch.mmu; > + union kvm_mmu_role new_role = > + kvm_calc_shadow_mmu_root_page_role(vcpu, false); > + > + if (new_role.as_u64 != context->mmu_role.as_u64) > + shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role); > +} > + > +void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer, > + gpa_t nested_cr3) > +{ > + struct kvm_mmu *context = vcpu->arch.mmu; > + union kvm_mmu_role new_role = > + kvm_calc_shadow_mmu_root_page_role(vcpu, false); > + > + if (new_role.as_u64 != context->mmu_role.as_u64) > + shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role); > +} > +EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu); > > static union kvm_mmu_role As a follow up, the assignments to context should stop using vcpu->arch.mmu in favor of root_mmu/guest_mmu. Paolo ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest 2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov 2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov @ 2020-07-08 9:36 ` Vitaly Kuznetsov 2020-07-08 11:49 ` Paolo Bonzini 2020-07-08 9:36 ` [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov 2 siblings, 1 reply; 7+ messages in thread From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw) To: kvm, Paolo Bonzini Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid, linux-kernel Undesired triple fault gets injected to L1 guest on SVM when L2 is launched with certain CR3 values. #TF is raised by mmu_check_root() check in fast_pgd_switch() and the root cause is that when kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT enabled CR3 points to a nGPA so we can't check it with kvm_is_visible_gfn(). Calling kvm_mmu_new_pgd() with L2's CR3 idea when NPT is in use seems to be wrong, an acceptable place for it seems to be kvm_init_shadow_npt_mmu(). This also matches nVMX code. Fixes: 7c390d350f8b ("kvm: x86: Add fast CR3 switch code path") Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> --- arch/x86/include/asm/kvm_host.h | 7 ++++++- arch/x86/kvm/mmu/mmu.c | 2 ++ arch/x86/kvm/svm/nested.c | 2 +- arch/x86/kvm/x86.c | 8 +++++--- 4 files changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index be5363b21540..49b62f024f51 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1459,7 +1459,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index, int reason, bool has_error_code, u32 error_code); int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3); +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested); +static inline int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) +{ + return __kvm_set_cr3(vcpu, cr3, false); +} + int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4); int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8); int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val); diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 167d12ab957a..ebf0cb3f1ce0 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4987,6 +4987,8 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer, union kvm_mmu_role new_role = kvm_calc_shadow_mmu_root_page_role(vcpu, false); + __kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base, true, true); + if (new_role.as_u64 != context->mmu_role.as_u64) shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role); } diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index e424bce13e6c..b467917a9784 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -324,7 +324,7 @@ static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_v svm_set_efer(&svm->vcpu, nested_vmcb->save.efer); svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0); svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4); - (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3); + (void)__kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3, npt_enabled); svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = nested_vmcb->save.cr2; kvm_rax_write(&svm->vcpu, nested_vmcb->save.rax); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3b92db412335..3761135eb052 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1004,7 +1004,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) } EXPORT_SYMBOL_GPL(kvm_set_cr4); -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested) { bool skip_tlb_flush = false; #ifdef CONFIG_X86_64 @@ -1031,13 +1031,15 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) return 1; - kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush); + if (!cr3_is_nested) + kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush); + vcpu->arch.cr3 = cr3; kvm_register_mark_available(vcpu, VCPU_EXREG_CR3); return 0; } -EXPORT_SYMBOL_GPL(kvm_set_cr3); +EXPORT_SYMBOL_GPL(__kvm_set_cr3); int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8) { -- 2.25.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest 2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov @ 2020-07-08 11:49 ` Paolo Bonzini 2020-07-08 14:39 ` Vitaly Kuznetsov 0 siblings, 1 reply; 7+ messages in thread From: Paolo Bonzini @ 2020-07-08 11:49 UTC (permalink / raw) To: Vitaly Kuznetsov, kvm Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid, linux-kernel On 08/07/20 11:36, Vitaly Kuznetsov wrote: > Undesired triple fault gets injected to L1 guest on SVM when L2 is > launched with certain CR3 values. #TF is raised by mmu_check_root() > check in fast_pgd_switch() and the root cause is that when > kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT > enabled CR3 points to a nGPA so we can't check it with > kvm_is_visible_gfn(). > > Calling kvm_mmu_new_pgd() with L2's CR3 idea when NPT is in use > seems to be wrong, an acceptable place for it seems to be > kvm_init_shadow_npt_mmu(). This also matches nVMX code. > > Fixes: 7c390d350f8b ("kvm: x86: Add fast CR3 switch code path") > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > arch/x86/include/asm/kvm_host.h | 7 ++++++- > arch/x86/kvm/mmu/mmu.c | 2 ++ > arch/x86/kvm/svm/nested.c | 2 +- > arch/x86/kvm/x86.c | 8 +++++--- > 4 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index be5363b21540..49b62f024f51 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1459,7 +1459,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index, > int reason, bool has_error_code, u32 error_code); > > int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); > -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3); > +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested); > +static inline int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) > +{ > + return __kvm_set_cr3(vcpu, cr3, false); > +} > + > int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4); > int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8); > int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val); > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 167d12ab957a..ebf0cb3f1ce0 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4987,6 +4987,8 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer, > union kvm_mmu_role new_role = > kvm_calc_shadow_mmu_root_page_role(vcpu, false); > > + __kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base, true, true); > + > if (new_role.as_u64 != context->mmu_role.as_u64) > shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role); > } > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index e424bce13e6c..b467917a9784 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -324,7 +324,7 @@ static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_v > svm_set_efer(&svm->vcpu, nested_vmcb->save.efer); > svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0); > svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4); > - (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3); > + (void)__kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3, npt_enabled); > > svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = nested_vmcb->save.cr2; > kvm_rax_write(&svm->vcpu, nested_vmcb->save.rax); > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 3b92db412335..3761135eb052 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1004,7 +1004,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) > } > EXPORT_SYMBOL_GPL(kvm_set_cr4); > > -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) > +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested) > { > bool skip_tlb_flush = false; > #ifdef CONFIG_X86_64 > @@ -1031,13 +1031,15 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) > !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) > return 1; > > - kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush); > + if (!cr3_is_nested) > + kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush); > + > vcpu->arch.cr3 = cr3; > kvm_register_mark_available(vcpu, VCPU_EXREG_CR3); > > return 0; > } > -EXPORT_SYMBOL_GPL(kvm_set_cr3); > +EXPORT_SYMBOL_GPL(__kvm_set_cr3); > > int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8) > { > Instead of the new argument (which is not really named right since it's never true for !NPT) you could perhaps check vcpu->arch.mmu. But also, for NPT=1 the kvm_mmu_new_pgd is also unnecessary on vmexit, because the old roots are still valid (or has been invalidated otherwise) while L2 was running. I'm also not sure if skip_tlb_flush can use X86_CR3_PCID_NOFLUSH the way kvm_set_cr3 does, so I wouldn't mind duplicating the code completely as is already the case for nested_vmx_load_cr3. It would introduce some code duplication, but overall the code would be better. For now, there need not be an equivalent to nested_vmx_transition_mmu_sync, ASID handling can be left for later. Paolo ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest 2020-07-08 11:49 ` Paolo Bonzini @ 2020-07-08 14:39 ` Vitaly Kuznetsov 0 siblings, 0 replies; 7+ messages in thread From: Vitaly Kuznetsov @ 2020-07-08 14:39 UTC (permalink / raw) To: Paolo Bonzini, kvm Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid, linux-kernel Paolo Bonzini <pbonzini@redhat.com> writes: > On 08/07/20 11:36, Vitaly Kuznetsov wrote: >> Undesired triple fault gets injected to L1 guest on SVM when L2 is >> launched with certain CR3 values. #TF is raised by mmu_check_root() >> check in fast_pgd_switch() and the root cause is that when >> kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT >> enabled CR3 points to a nGPA so we can't check it with >> kvm_is_visible_gfn(). >> >> Calling kvm_mmu_new_pgd() with L2's CR3 idea when NPT is in use >> seems to be wrong, an acceptable place for it seems to be >> kvm_init_shadow_npt_mmu(). This also matches nVMX code. >> >> Fixes: 7c390d350f8b ("kvm: x86: Add fast CR3 switch code path") >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> >> --- >> arch/x86/include/asm/kvm_host.h | 7 ++++++- >> arch/x86/kvm/mmu/mmu.c | 2 ++ >> arch/x86/kvm/svm/nested.c | 2 +- >> arch/x86/kvm/x86.c | 8 +++++--- >> 4 files changed, 14 insertions(+), 5 deletions(-) >> >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >> index be5363b21540..49b62f024f51 100644 >> --- a/arch/x86/include/asm/kvm_host.h >> +++ b/arch/x86/include/asm/kvm_host.h >> @@ -1459,7 +1459,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index, >> int reason, bool has_error_code, u32 error_code); >> >> int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); >> -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3); >> +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested); >> +static inline int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) >> +{ >> + return __kvm_set_cr3(vcpu, cr3, false); >> +} >> + >> int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4); >> int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8); >> int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val); >> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c >> index 167d12ab957a..ebf0cb3f1ce0 100644 >> --- a/arch/x86/kvm/mmu/mmu.c >> +++ b/arch/x86/kvm/mmu/mmu.c >> @@ -4987,6 +4987,8 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer, >> union kvm_mmu_role new_role = >> kvm_calc_shadow_mmu_root_page_role(vcpu, false); >> >> + __kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base, true, true); >> + >> if (new_role.as_u64 != context->mmu_role.as_u64) >> shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role); >> } >> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c >> index e424bce13e6c..b467917a9784 100644 >> --- a/arch/x86/kvm/svm/nested.c >> +++ b/arch/x86/kvm/svm/nested.c >> @@ -324,7 +324,7 @@ static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_v >> svm_set_efer(&svm->vcpu, nested_vmcb->save.efer); >> svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0); >> svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4); >> - (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3); >> + (void)__kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3, npt_enabled); >> >> svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = nested_vmcb->save.cr2; >> kvm_rax_write(&svm->vcpu, nested_vmcb->save.rax); >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 3b92db412335..3761135eb052 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -1004,7 +1004,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) >> } >> EXPORT_SYMBOL_GPL(kvm_set_cr4); >> >> -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) >> +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested) >> { >> bool skip_tlb_flush = false; >> #ifdef CONFIG_X86_64 >> @@ -1031,13 +1031,15 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) >> !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) >> return 1; >> >> - kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush); >> + if (!cr3_is_nested) >> + kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush); >> + >> vcpu->arch.cr3 = cr3; >> kvm_register_mark_available(vcpu, VCPU_EXREG_CR3); >> >> return 0; >> } >> -EXPORT_SYMBOL_GPL(kvm_set_cr3); >> +EXPORT_SYMBOL_GPL(__kvm_set_cr3); >> >> int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8) >> { >> > > Instead of the new argument (which is not really named right since it's > never true for !NPT) you could perhaps check vcpu->arch.mmu. But also, > for NPT=1 the kvm_mmu_new_pgd is also unnecessary on vmexit, because the > old roots are still valid (or has been invalidated otherwise) while L2 > was running. > > I'm also not sure if skip_tlb_flush can use X86_CR3_PCID_NOFLUSH the way > kvm_set_cr3 does, so I wouldn't mind duplicating the code completely as > is already the case for nested_vmx_load_cr3. It would introduce some > code duplication, but overall the code would be better. For now, there > need not be an equivalent to nested_vmx_transition_mmu_sync, ASID > handling can be left for later. Sounds reasonable, let's introduce nested_svm_load_cr3() to not mix these two concepts together. I'll be back with v3 shortly, thanks! -- Vitaly ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() 2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov 2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov 2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov @ 2020-07-08 9:36 ` Vitaly Kuznetsov 2 siblings, 0 replies; 7+ messages in thread From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw) To: kvm, Paolo Bonzini Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid, linux-kernel The mmu_check_root() check in fast_pgd_switch() seems to be superfluous: when GPA is outside of the visible range cached_root_available() will fail for non-direct roots (as we can't have a matching one on the list) and we don't seem to care for direct ones. Also, raising #TF immediately when a non-existent GFN is written to CR3 doesn't seem to mach architectural behavior. Drop the check. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> --- arch/x86/kvm/mmu/mmu.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index ebf0cb3f1ce0..16c7701f1741 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4277,8 +4277,7 @@ static bool fast_pgd_switch(struct kvm_vcpu *vcpu, gpa_t new_pgd, */ if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL && mmu->root_level >= PT64_ROOT_4LEVEL) - return !mmu_check_root(vcpu, new_pgd >> PAGE_SHIFT) && - cached_root_available(vcpu, new_pgd, new_role); + return cached_root_available(vcpu, new_pgd, new_role); return false; } -- 2.25.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-07-08 14:39 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov 2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov 2020-07-08 11:25 ` Paolo Bonzini 2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov 2020-07-08 11:49 ` Paolo Bonzini 2020-07-08 14:39 ` Vitaly Kuznetsov 2020-07-08 9:36 ` [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov
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