From 4f2e7aa1cfdf4374a4c876c9358e0d7035647eb1 Mon Sep 17 00:00:00 2001 From: Michael Roth Date: Wed, 1 May 2024 03:52:03 -0500 Subject: [PATCH] KVM: SEV: Implement gmem hook for initializing private pages This will handle the RMP table updates needed to put a page into a private state before mapping it into an SEV-SNP guest. Reviewed-by: Paolo Bonzini Signed-off-by: Michael Roth Message-ID: <20240501085210.2213060-14-michael.roth@amd.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/svm/sev.c | 98 ++++++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/svm/svm.c | 2 + arch/x86/kvm/svm/svm.h | 5 +++ arch/x86/kvm/x86.c | 5 +++ virt/kvm/guest_memfd.c | 4 +- 6 files changed, 113 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index 5e72faca4e8f..10768f13b240 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -137,6 +137,7 @@ config KVM_AMD_SEV depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m) select ARCH_HAS_CC_PLATFORM select KVM_GENERIC_PRIVATE_MEM + select HAVE_KVM_GMEM_PREPARE help Provides support for launching Encrypted VMs (SEV) and Encrypted VMs with Encrypted State (SEV-ES) on AMD processors. diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 0c1108ffc4ae..0ed6b96c01c3 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -4565,3 +4565,101 @@ out: out_no_trace: put_page(pfn_to_page(pfn)); } + +static bool is_pfn_range_shared(kvm_pfn_t start, kvm_pfn_t end) +{ + kvm_pfn_t pfn = start; + + while (pfn < end) { + int ret, rmp_level; + bool assigned; + + ret = snp_lookup_rmpentry(pfn, &assigned, &rmp_level); + if (ret) { + pr_warn_ratelimited("SEV: Failed to retrieve RMP entry: PFN 0x%llx GFN start 0x%llx GFN end 0x%llx RMP level %d error %d\n", + pfn, start, end, rmp_level, ret); + return false; + } + + if (assigned) { + pr_debug("%s: overlap detected, PFN 0x%llx start 0x%llx end 0x%llx RMP level %d\n", + __func__, pfn, start, end, rmp_level); + return false; + } + + pfn++; + } + + return true; +} + +static u8 max_level_for_order(int order) +{ + if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M)) + return PG_LEVEL_2M; + + return PG_LEVEL_4K; +} + +static bool is_large_rmp_possible(struct kvm *kvm, kvm_pfn_t pfn, int order) +{ + kvm_pfn_t pfn_aligned = ALIGN_DOWN(pfn, PTRS_PER_PMD); + + /* + * If this is a large folio, and the entire 2M range containing the + * PFN is currently shared, then the entire 2M-aligned range can be + * set to private via a single 2M RMP entry. + */ + if (max_level_for_order(order) > PG_LEVEL_4K && + is_pfn_range_shared(pfn_aligned, pfn_aligned + PTRS_PER_PMD)) + return true; + + return false; +} + +int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order) +{ + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + kvm_pfn_t pfn_aligned; + gfn_t gfn_aligned; + int level, rc; + bool assigned; + + if (!sev_snp_guest(kvm)) + return 0; + + rc = snp_lookup_rmpentry(pfn, &assigned, &level); + if (rc) { + pr_err_ratelimited("SEV: Failed to look up RMP entry: GFN %llx PFN %llx error %d\n", + gfn, pfn, rc); + return -ENOENT; + } + + if (assigned) { + pr_debug("%s: already assigned: gfn %llx pfn %llx max_order %d level %d\n", + __func__, gfn, pfn, max_order, level); + return 0; + } + + if (is_large_rmp_possible(kvm, pfn, max_order)) { + level = PG_LEVEL_2M; + pfn_aligned = ALIGN_DOWN(pfn, PTRS_PER_PMD); + gfn_aligned = ALIGN_DOWN(gfn, PTRS_PER_PMD); + } else { + level = PG_LEVEL_4K; + pfn_aligned = pfn; + gfn_aligned = gfn; + } + + rc = rmp_make_private(pfn_aligned, gfn_to_gpa(gfn_aligned), level, sev->asid, false); + if (rc) { + pr_err_ratelimited("SEV: Failed to update RMP entry: GFN %llx PFN %llx level %d error %d\n", + gfn, pfn, level, rc); + return -EINVAL; + } + + pr_debug("%s: updated: gfn %llx pfn %llx pfn_aligned %llx max_order %d level %d\n", + __func__, gfn, pfn, pfn_aligned, max_order, level); + + return 0; +} diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 546656606b44..b9ecc06f8934 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5081,6 +5081,8 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { .vcpu_deliver_sipi_vector = svm_vcpu_deliver_sipi_vector, .vcpu_get_apicv_inhibit_reasons = avic_vcpu_get_apicv_inhibit_reasons, .alloc_apic_backing_page = svm_alloc_apic_backing_page, + + .gmem_prepare = sev_gmem_prepare, }; /* diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 926bfce571a6..4203bd9012e9 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -736,6 +736,7 @@ extern unsigned int max_sev_asid; void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code); void sev_vcpu_unblocking(struct kvm_vcpu *vcpu); void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu); +int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order); #else static inline struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu) { return alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); @@ -752,6 +753,10 @@ static inline int sev_dev_get_attr(u32 group, u64 attr, u64 *val) { return -ENXI static inline void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code) {} static inline void sev_vcpu_unblocking(struct kvm_vcpu *vcpu) {} static inline void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu) {} +static inline int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order) +{ + return 0; +} #endif diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d29477910ffa..d750546ec934 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -13611,6 +13611,11 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) EXPORT_SYMBOL_GPL(kvm_arch_no_poll); #ifdef CONFIG_HAVE_KVM_GMEM_PREPARE +bool kvm_arch_gmem_prepare_needed(struct kvm *kvm) +{ + return kvm->arch.vm_type == KVM_X86_SNP_VM; +} + int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order) { return static_call(kvm_x86_gmem_prepare)(kvm, pfn, gfn, max_order); diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index dfe50c64a552..9714add38852 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -39,8 +39,8 @@ static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct fol gfn = slot->base_gfn + index - slot->gmem.pgoff; rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, compound_order(compound_head(page))); if (rc) { - pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx, error %d.\n", - index, rc); + pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx GFN %llx PFN %llx error %d.\n", + index, gfn, pfn, rc); return rc; } }