Messages in this thread |  | | Date | Thu, 17 Nov 2022 14:28:03 -0600 | Subject | Re: [PATCH Part2 v6 39/49] KVM: SVM: Introduce ops for the post gfn map and unmap | From | "Kalra, Ashish" <> |
| |
On 11/17/2022 2:18 PM, Peter Gonda wrote: > On Wed, Aug 17, 2022 at 9:47 PM Alper Gun <alpergun@google.com> wrote: >> >> On Mon, Jun 20, 2022 at 4:12 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote: >>> >>> From: Brijesh Singh <brijesh.singh@amd.com> >>> >>> When SEV-SNP is enabled in the guest VM, the guest memory pages can >>> either be a private or shared. A write from the hypervisor goes through >>> the RMP checks. If hardware sees that hypervisor is attempting to write >>> to a guest private page, then it triggers an RMP violation #PF. >>> >>> To avoid the RMP violation with GHCB pages, added new post_{map,unmap}_gfn >>> functions to verify if its safe to map GHCB pages. Uses a spinlock to >>> protect against the page state change for existing mapped pages. >>> >>> Need to add generic post_{map,unmap}_gfn() ops that can be used to verify >>> that its safe to map a given guest page in the hypervisor. >>> >>> This patch will need to be revisited later after consensus is reached on >>> how to manage guest private memory as probably UPM private memslots will >>> be able to handle this page state change more gracefully. >>> >>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> >>> Signed-off by: Ashish Kalra <ashish.kalra@amd.com> >>> --- >>> arch/x86/include/asm/kvm-x86-ops.h | 1 + >>> arch/x86/include/asm/kvm_host.h | 3 ++ >>> arch/x86/kvm/svm/sev.c | 48 ++++++++++++++++++++++++++++-- >>> arch/x86/kvm/svm/svm.c | 3 ++ >>> arch/x86/kvm/svm/svm.h | 11 +++++++ >>> 5 files changed, 64 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h >>> index e0068e702692..2dd2bc0cf4c3 100644 >>> --- a/arch/x86/include/asm/kvm-x86-ops.h >>> +++ b/arch/x86/include/asm/kvm-x86-ops.h >>> @@ -130,6 +130,7 @@ KVM_X86_OP(vcpu_deliver_sipi_vector) >>> KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons); >>> KVM_X86_OP(alloc_apic_backing_page) >>> KVM_X86_OP_OPTIONAL(rmp_page_level_adjust) >>> +KVM_X86_OP(update_protected_guest_state) >>> >>> #undef KVM_X86_OP >>> #undef KVM_X86_OP_OPTIONAL >>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >>> index 49b217dc8d7e..8abc0e724f5c 100644 >>> --- a/arch/x86/include/asm/kvm_host.h >>> +++ b/arch/x86/include/asm/kvm_host.h >>> @@ -1522,7 +1522,10 @@ struct kvm_x86_ops { >>> unsigned long (*vcpu_get_apicv_inhibit_reasons)(struct kvm_vcpu *vcpu); >>> >>> void *(*alloc_apic_backing_page)(struct kvm_vcpu *vcpu); >>> + >>> void (*rmp_page_level_adjust)(struct kvm *kvm, kvm_pfn_t pfn, int *level); >>> + >>> + int (*update_protected_guest_state)(struct kvm_vcpu *vcpu); >>> }; >>> >>> struct kvm_x86_nested_ops { >>> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c >>> index cb2d1bbb862b..4ed90331bca0 100644 >>> --- a/arch/x86/kvm/svm/sev.c >>> +++ b/arch/x86/kvm/svm/sev.c >>> @@ -341,6 +341,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp) >>> if (ret) >>> goto e_free; >>> >>> + spin_lock_init(&sev->psc_lock); >>> ret = sev_snp_init(&argp->error); >>> } else { >>> ret = sev_platform_init(&argp->error); >>> @@ -2828,19 +2829,28 @@ static inline int svm_map_ghcb(struct vcpu_svm *svm, struct kvm_host_map *map) >>> { >>> struct vmcb_control_area *control = &svm->vmcb->control; >>> u64 gfn = gpa_to_gfn(control->ghcb_gpa); >>> + struct kvm_vcpu *vcpu = &svm->vcpu; >>> >>> - if (kvm_vcpu_map(&svm->vcpu, gfn, map)) { >>> + if (kvm_vcpu_map(vcpu, gfn, map)) { >>> /* Unable to map GHCB from guest */ >>> pr_err("error mapping GHCB GFN [%#llx] from guest\n", gfn); >>> return -EFAULT; >>> } >>> >>> + if (sev_post_map_gfn(vcpu->kvm, map->gfn, map->pfn)) { >>> + kvm_vcpu_unmap(vcpu, map, false); >>> + return -EBUSY; >>> + } >>> + >>> return 0; >>> } >>> >>> static inline void svm_unmap_ghcb(struct vcpu_svm *svm, struct kvm_host_map *map) >>> { >>> - kvm_vcpu_unmap(&svm->vcpu, map, true); >>> + struct kvm_vcpu *vcpu = &svm->vcpu; >>> + >>> + kvm_vcpu_unmap(vcpu, map, true); >>> + sev_post_unmap_gfn(vcpu->kvm, map->gfn, map->pfn); >>> } >>> >>> static void dump_ghcb(struct vcpu_svm *svm) >>> @@ -3383,6 +3393,8 @@ static int __snp_handle_page_state_change(struct kvm_vcpu *vcpu, enum psc_op op, >>> return PSC_UNDEF_ERR; >>> } >>> >>> + spin_lock(&sev->psc_lock); >>> + >>> write_lock(&kvm->mmu_lock); >>> >>> rc = kvm_mmu_get_tdp_walk(vcpu, gpa, &pfn, &npt_level); >>> @@ -3417,6 +3429,8 @@ static int __snp_handle_page_state_change(struct kvm_vcpu *vcpu, enum psc_op op, >>> >>> write_unlock(&kvm->mmu_lock); >>> >>> + spin_unlock(&sev->psc_lock); >> >> There is a corner case where the psc_lock is not released. If >> kvm_mmu_get_tdp_walk fails, the lock will be kept and will cause soft >> lockup. >> >>> + >>> if (rc) { >>> pr_err_ratelimited("Error op %d gpa %llx pfn %llx level %d rc %d\n", >>> op, gpa, pfn, level, rc); >>> @@ -3965,3 +3979,33 @@ void sev_rmp_page_level_adjust(struct kvm *kvm, kvm_pfn_t pfn, int *level) >>> /* Adjust the level to keep the NPT and RMP in sync */ >>> *level = min_t(size_t, *level, rmp_level); >>> } >>> + >>> +int sev_post_map_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn) >>> +{ >>> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; >>> + int level; >>> + >>> + if (!sev_snp_guest(kvm)) >>> + return 0; >>> + >>> + spin_lock(&sev->psc_lock); >>> + >>> + /* If pfn is not added as private then fail */ >>> + if (snp_lookup_rmpentry(pfn, &level) == 1) { >>> + spin_unlock(&sev->psc_lock); >>> + pr_err_ratelimited("failed to map private gfn 0x%llx pfn 0x%llx\n", gfn, pfn); >>> + return -EBUSY; >>> + } >>> + >>> + return 0; >>> +} >>> + >>> +void sev_post_unmap_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn) >>> +{ >>> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; >>> + >>> + if (!sev_snp_guest(kvm)) >>> + return; >>> + >>> + spin_unlock(&sev->psc_lock); >>> +} >>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >>> index b24e0171cbf2..1c8e035ba011 100644 >>> --- a/arch/x86/kvm/svm/svm.c >>> +++ b/arch/x86/kvm/svm/svm.c >>> @@ -4734,7 +4734,10 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { >>> .vcpu_get_apicv_inhibit_reasons = avic_vcpu_get_apicv_inhibit_reasons, >>> >>> .alloc_apic_backing_page = svm_alloc_apic_backing_page, >>> + >>> .rmp_page_level_adjust = sev_rmp_page_level_adjust, >>> + >>> + .update_protected_guest_state = sev_snp_update_protected_guest_state, >>> }; > > I don't see this function sev_snp_update_protected_guest_state() being > defined anywhere in this series. > > Then this line is removed in 'KVM: SVM: Support SEV-SNP AP Creation > NAE event'. Should this line just be removed from this patch in the > first place?
Yes, already fixed for v7.
> >>> >>> /* >>> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h >>> index 54ff56cb6125..3fd95193ed8d 100644 >>> --- a/arch/x86/kvm/svm/svm.h >>> +++ b/arch/x86/kvm/svm/svm.h >>> @@ -79,19 +79,25 @@ struct kvm_sev_info { >>> bool active; /* SEV enabled guest */ >>> bool es_active; /* SEV-ES enabled guest */ >>> bool snp_active; /* SEV-SNP enabled guest */ >>> + >>> unsigned int asid; /* ASID used for this guest */ >>> unsigned int handle; /* SEV firmware handle */ >>> int fd; /* SEV device fd */ >>> + >>> unsigned long pages_locked; /* Number of pages locked */ >>> struct list_head regions_list; /* List of registered regions */ >>> + >>> u64 ap_jump_table; /* SEV-ES AP Jump Table address */ >>> + >>> struct kvm *enc_context_owner; /* Owner of copied encryption context */ >>> struct list_head mirror_vms; /* List of VMs mirroring */ >>> struct list_head mirror_entry; /* Use as a list entry of mirrors */ >>> struct misc_cg *misc_cg; /* For misc cgroup accounting */ >>> atomic_t migration_in_progress; >>> + >>> u64 snp_init_flags; >>> void *snp_context; /* SNP guest context page */ >>> + spinlock_t psc_lock; >>> }; >>> >>> struct kvm_svm { >>> @@ -702,6 +708,11 @@ void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa); >>> void sev_es_unmap_ghcb(struct vcpu_svm *svm); >>> struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu); >>> void sev_rmp_page_level_adjust(struct kvm *kvm, kvm_pfn_t pfn, int *level); >>> +int sev_post_map_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn); >>> +void sev_post_unmap_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn); >>> +void handle_rmp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code); >>> +void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu); >>> +int sev_snp_update_protected_guest_state(struct kvm_vcpu *vcpu); > > Ditto should this be removed? > Yes, already fixed for v7.
Thanks, Ashish
>>> >>> /* vmenter.S */ >>> >>> -- >>> 2.25.1 >>>
|  |