Message ID | a02d8e9a3c46b9627a5edccd76416abeccf45a20.1659854790.git.isaku.yamahata@intel.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | KVM TDX basic feature support | expand |
On Sun, Aug 07, 2022 at 03:01:27PM -0700, isaku.yamahata@intel.com wrote: > From: Isaku Yamahata <isaku.yamahata@intel.com> > > For private GPA, CPU refers a private page table whose contents are > encrypted. The dedicated APIs to operate on it (e.g. updating/reading its > PTE entry) are used and their cost is expensive. > > When KVM resolves KVM page fault, it walks the page tables. To reuse the > existing KVM MMU code and mitigate the heavy cost to directly walk > protected (encrypted) page table, allocate one more page to copy the > protected page table for KVM MMU code to directly walk. Resolve KVM page > fault with the existing code, and do additional operations necessary for > the protected page table. To distinguish such cases, the existing KVM page > table is called a shared page table (i.e. not associated with protected > page table), and the page table with protected page table is called a > private page table. The relationship is depicted below. > > Add a private pointer to struct kvm_mmu_page for protected page table and > add helper functions to allocate/initialize/free a protected page table > page. > > KVM page fault | > | | > V | > -------------+---------- | > | | | > V V | > shared GPA private GPA | > | | | > V V | > shared PT root private PT root | protected PT root > | | | | > V V | V > shared PT private PT ----propagate----> protected PT > | | | | > | \-----------------+------\ | > | | | | > V | V V > shared guest page | private guest page > | > non-encrypted memory | encrypted memory > | > PT: page table > - Shared PT is visible to KVM and it is used by CPU. > - Protected PT is used by CPU but it is invisible to KVM. > - Private PT is visible to KVM but not used by CPU. It is used to > propagate PT change to the actual protected PT which is used by CPU. > > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/mmu/mmu.c | 9 ++++ > arch/x86/kvm/mmu/mmu_internal.h | 73 +++++++++++++++++++++++++++++++++ > arch/x86/kvm/mmu/tdp_mmu.c | 2 + > 4 files changed, 85 insertions(+) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 25835b8c4c12..e4ecf6b8ea0b 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -743,6 +743,7 @@ struct kvm_vcpu_arch { > struct kvm_mmu_memory_cache mmu_shadow_page_cache; > struct kvm_mmu_memory_cache mmu_shadowed_info_cache; > struct kvm_mmu_memory_cache mmu_page_header_cache; > + struct kvm_mmu_memory_cache mmu_private_sp_cache; > > /* > * QEMU userspace and the guest each have their own FPU state. > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 0e5a6dcc4966..aa0819905874 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -669,6 +669,13 @@ static int mmu_topup_shadow_page_cache(struct kvm_vcpu *vcpu) > struct kvm_mmu_memory_cache *mc = &vcpu->arch.mmu_shadow_page_cache; > int start, end, i, r; > > + if (kvm_gfn_shared_mask(vcpu->kvm)) { > + r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_private_sp_cache, > + PT64_ROOT_MAX_LEVEL); > + if (r) > + return r; > + } > + > start = kvm_mmu_memory_cache_nr_free_objects(mc); > r = kvm_mmu_topup_memory_cache(mc, PT64_ROOT_MAX_LEVEL); > > @@ -718,6 +725,7 @@ static void mmu_free_memory_caches(struct kvm_vcpu *vcpu) > kvm_mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache); > kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache); > kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadowed_info_cache); > + kvm_mmu_free_memory_cache(&vcpu->arch.mmu_private_sp_cache); > kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache); > } > > @@ -2162,6 +2170,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm, > sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache); > > set_page_private(virt_to_page(sp->spt), (unsigned long)sp); > + kvm_mmu_init_private_sp(sp, NULL); > > /* > * active_mmu_pages must be a FIFO list, as kvm_zap_obsolete_pages() > diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h > index c9446e4e16e3..d43c01e7e37b 100644 > --- a/arch/x86/kvm/mmu/mmu_internal.h > +++ b/arch/x86/kvm/mmu/mmu_internal.h > @@ -82,6 +82,10 @@ struct kvm_mmu_page { > */ > u64 *shadowed_translation; > > +#ifdef CONFIG_KVM_MMU_PRIVATE > + /* associated private shadow page, e.g. SEPT page. */ > + void *private_sp; > +#endif > /* Currently serving as active root */ > union { > int root_count; > @@ -153,6 +157,75 @@ static inline bool is_private_sptep(u64 *sptep) > return is_private_sp(sptep_to_sp(sptep)); > } > > +#ifdef CONFIG_KVM_MMU_PRIVATE > +static inline void *kvm_mmu_private_sp(struct kvm_mmu_page *sp) > +{ > + return sp->private_sp; > +} > + > +static inline void kvm_mmu_init_private_sp(struct kvm_mmu_page *sp, void *private_sp) > +{ > + sp->private_sp = private_sp; > +} How about "kvm_mmu_set_private_sp()" ? Because it just sets variable. "init" means things more than just setting. > + > +static inline void kvm_mmu_alloc_private_sp( > + struct kvm_vcpu *vcpu, struct kvm_mmu_memory_cache *private_sp_cache, > + struct kvm_mmu_page *sp) > +{ > + /* > + * vcpu == NULL means non-root SPT: > + * vcpu == NULL is used to split a large SPT into smaller SPT. Root SPT > + * is not a large SPT. > + */ Can we rely on sp->tdp_mmu_root_count to know it's root or not ? Depends on vcpu looks odd, because it's often to split huge pages in per-vcpu level, or things I missed here... > + bool is_root = vcpu && > + vcpu->arch.root_mmu.root_role.level == sp->role.level; > + > + if (vcpu) > + private_sp_cache = &vcpu->arch.mmu_private_sp_cache; how about totally rely on caller for this, e.g caller to decide uses per-vcpu cache or per-VM cache ? > + WARN_ON(!kvm_mmu_page_role_is_private(sp->role)); Please move to begin of this function because this should be first step to check bad cases. > + if (is_root) > + /* > + * Because TDX module assigns root Secure-EPT page and set it to > + * Secure-EPTP when TD vcpu is created, secure page table for > + * root isn't needed. > + */ > + sp->private_sp = NULL; > + else { > + sp->private_sp = kvm_mmu_memory_cache_alloc(private_sp_cache); > + /* > + * Because mmu_private_sp_cache is topped up before staring kvm > + * page fault resolving, the allocation above shouldn't fail. > + */ > + WARN_ON_ONCE(!sp->private_sp); > + } > +} > + > +static inline void kvm_mmu_free_private_sp(struct kvm_mmu_page *sp) > +{ > + if (sp->private_sp) > + free_page((unsigned long)sp->private_sp); > +} > +#else > +static inline void *kvm_mmu_private_sp(struct kvm_mmu_page *sp) > +{ > + return NULL; > +} > + > +static inline void kvm_mmu_init_private_sp(struct kvm_mmu_page *sp, void *private_sp) > +{ > +} > + > +static inline void kvm_mmu_alloc_private_sp( > + struct kvm_vcpu *vcpu, struct kvm_mmu_memory_cache *private_sp_cache, > + struct kvm_mmu_page *sp) > +{ > +} > + > +static inline void kvm_mmu_free_private_sp(struct kvm_mmu_page *sp) > +{ > +} > +#endif > + > static inline bool kvm_mmu_page_ad_need_write_protect(struct kvm_mmu_page *sp) > { > /* > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > index 823c1ef807eb..3f5b019f9774 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.c > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > @@ -71,6 +71,7 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) > > static void tdp_mmu_free_sp(struct kvm_mmu_page *sp) > { > + kvm_mmu_free_private_sp(sp); > free_page((unsigned long)sp->spt); > kmem_cache_free(mmu_page_header_cache, sp); > } > @@ -300,6 +301,7 @@ static void tdp_mmu_init_sp(struct kvm_mmu_page *sp, tdp_ptep_t sptep, > sp->gfn = gfn; > sp->ptep = sptep; > sp->tdp_mmu_page = true; > + kvm_mmu_init_private_sp(sp, NULL); This set the private sp allocated by kvm_mmu_alloc_private_sp(), I think it's wrong here. > > trace_kvm_mmu_get_page(sp, true); > } > -- > 2.25.1 >
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 25835b8c4c12..e4ecf6b8ea0b 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -743,6 +743,7 @@ struct kvm_vcpu_arch { struct kvm_mmu_memory_cache mmu_shadow_page_cache; struct kvm_mmu_memory_cache mmu_shadowed_info_cache; struct kvm_mmu_memory_cache mmu_page_header_cache; + struct kvm_mmu_memory_cache mmu_private_sp_cache; /* * QEMU userspace and the guest each have their own FPU state. diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 0e5a6dcc4966..aa0819905874 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -669,6 +669,13 @@ static int mmu_topup_shadow_page_cache(struct kvm_vcpu *vcpu) struct kvm_mmu_memory_cache *mc = &vcpu->arch.mmu_shadow_page_cache; int start, end, i, r; + if (kvm_gfn_shared_mask(vcpu->kvm)) { + r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_private_sp_cache, + PT64_ROOT_MAX_LEVEL); + if (r) + return r; + } + start = kvm_mmu_memory_cache_nr_free_objects(mc); r = kvm_mmu_topup_memory_cache(mc, PT64_ROOT_MAX_LEVEL); @@ -718,6 +725,7 @@ static void mmu_free_memory_caches(struct kvm_vcpu *vcpu) kvm_mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache); kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache); kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadowed_info_cache); + kvm_mmu_free_memory_cache(&vcpu->arch.mmu_private_sp_cache); kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache); } @@ -2162,6 +2170,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm, sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache); set_page_private(virt_to_page(sp->spt), (unsigned long)sp); + kvm_mmu_init_private_sp(sp, NULL); /* * active_mmu_pages must be a FIFO list, as kvm_zap_obsolete_pages() diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index c9446e4e16e3..d43c01e7e37b 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -82,6 +82,10 @@ struct kvm_mmu_page { */ u64 *shadowed_translation; +#ifdef CONFIG_KVM_MMU_PRIVATE + /* associated private shadow page, e.g. SEPT page. */ + void *private_sp; +#endif /* Currently serving as active root */ union { int root_count; @@ -153,6 +157,75 @@ static inline bool is_private_sptep(u64 *sptep) return is_private_sp(sptep_to_sp(sptep)); } +#ifdef CONFIG_KVM_MMU_PRIVATE +static inline void *kvm_mmu_private_sp(struct kvm_mmu_page *sp) +{ + return sp->private_sp; +} + +static inline void kvm_mmu_init_private_sp(struct kvm_mmu_page *sp, void *private_sp) +{ + sp->private_sp = private_sp; +} + +static inline void kvm_mmu_alloc_private_sp( + struct kvm_vcpu *vcpu, struct kvm_mmu_memory_cache *private_sp_cache, + struct kvm_mmu_page *sp) +{ + /* + * vcpu == NULL means non-root SPT: + * vcpu == NULL is used to split a large SPT into smaller SPT. Root SPT + * is not a large SPT. + */ + bool is_root = vcpu && + vcpu->arch.root_mmu.root_role.level == sp->role.level; + + if (vcpu) + private_sp_cache = &vcpu->arch.mmu_private_sp_cache; + WARN_ON(!kvm_mmu_page_role_is_private(sp->role)); + if (is_root) + /* + * Because TDX module assigns root Secure-EPT page and set it to + * Secure-EPTP when TD vcpu is created, secure page table for + * root isn't needed. + */ + sp->private_sp = NULL; + else { + sp->private_sp = kvm_mmu_memory_cache_alloc(private_sp_cache); + /* + * Because mmu_private_sp_cache is topped up before staring kvm + * page fault resolving, the allocation above shouldn't fail. + */ + WARN_ON_ONCE(!sp->private_sp); + } +} + +static inline void kvm_mmu_free_private_sp(struct kvm_mmu_page *sp) +{ + if (sp->private_sp) + free_page((unsigned long)sp->private_sp); +} +#else +static inline void *kvm_mmu_private_sp(struct kvm_mmu_page *sp) +{ + return NULL; +} + +static inline void kvm_mmu_init_private_sp(struct kvm_mmu_page *sp, void *private_sp) +{ +} + +static inline void kvm_mmu_alloc_private_sp( + struct kvm_vcpu *vcpu, struct kvm_mmu_memory_cache *private_sp_cache, + struct kvm_mmu_page *sp) +{ +} + +static inline void kvm_mmu_free_private_sp(struct kvm_mmu_page *sp) +{ +} +#endif + static inline bool kvm_mmu_page_ad_need_write_protect(struct kvm_mmu_page *sp) { /* diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 823c1ef807eb..3f5b019f9774 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -71,6 +71,7 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) static void tdp_mmu_free_sp(struct kvm_mmu_page *sp) { + kvm_mmu_free_private_sp(sp); free_page((unsigned long)sp->spt); kmem_cache_free(mmu_page_header_cache, sp); } @@ -300,6 +301,7 @@ static void tdp_mmu_init_sp(struct kvm_mmu_page *sp, tdp_ptep_t sptep, sp->gfn = gfn; sp->ptep = sptep; sp->tdp_mmu_page = true; + kvm_mmu_init_private_sp(sp, NULL); trace_kvm_mmu_get_page(sp, true); }