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[20/21] KVM: x86: Add gmem hook for invalidating memory

Message ID 20240227232100.478238-21-pbonzini@redhat.com (mailing list archive)
State New, archived
Headers show
Series TDX/SNP part 1 of n, for 6.9 | expand

Commit Message

Paolo Bonzini Feb. 27, 2024, 11:20 p.m. UTC 
From: Michael Roth <michael.roth@amd.com>

In some cases, like with SEV-SNP, guest memory needs to be updated in a
platform-specific manner before it can be safely freed back to the host.
Wire up arch-defined hooks to the .free_folio kvm_gmem_aops callback to
allow for special handling of this sort when freeing memory in response
to FALLOC_FL_PUNCH_HOLE operations and when releasing the inode, and go
ahead and define an arch-specific hook for x86 since it will be needed
for handling memory used for SEV-SNP guests.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-Id: <20231230172351.574091-6-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm-x86-ops.h |  1 +
 arch/x86/include/asm/kvm_host.h    |  1 +
 arch/x86/kvm/x86.c                 |  7 +++++++
 include/linux/kvm_host.h           |  4 ++++
 virt/kvm/Kconfig                   |  4 ++++
 virt/kvm/guest_memfd.c             | 14 ++++++++++++++
 6 files changed, 31 insertions(+)
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Patch

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index adfaad15e7e6..42474acb7375 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -140,6 +140,7 @@  KVM_X86_OP(vcpu_deliver_sipi_vector)
 KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons);
 KVM_X86_OP_OPTIONAL(get_untagged_addr)
 KVM_X86_OP_OPTIONAL_RET0(gmem_prepare)
+KVM_X86_OP_OPTIONAL(gmem_invalidate)
 
 #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 6d873d08f739..e523b204697d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1805,6 +1805,7 @@  struct kvm_x86_ops {
 
 	gva_t (*get_untagged_addr)(struct kvm_vcpu *vcpu, gva_t gva, unsigned int flags);
 	int (*gmem_prepare)(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order);
+	void (*gmem_invalidate)(kvm_pfn_t start, kvm_pfn_t end);
 };
 
 struct kvm_x86_nested_ops {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index eff532ea59c9..9d5603adf542 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13605,6 +13605,13 @@  int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_ord
 }
 #endif
 
+#ifdef CONFIG_HAVE_KVM_GMEM_INVALIDATE
+void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
+{
+	static_call_cond(kvm_x86_gmem_invalidate)(start, end);
+}
+#endif
+
 int kvm_spec_ctrl_test_value(u64 value)
 {
 	/*
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 192c58116220..3835732491b9 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2465,4 +2465,8 @@  static inline int kvm_gmem_undo_get_pfn(struct kvm *kvm,
 int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order);
 #endif
 
+#ifdef CONFIG_HAVE_KVM_GMEM_INVALIDATE
+void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end);
+#endif
+
 #endif
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index dcce0c3b5b13..39356f5babbd 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -115,3 +115,7 @@  config KVM_GENERIC_PRIVATE_MEM
 config HAVE_KVM_GMEM_PREPARE
        bool
        depends on KVM_PRIVATE_MEM
+
+config HAVE_KVM_GMEM_INVALIDATE
+       bool
+       depends on KVM_PRIVATE_MEM
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 535ef1aa34fb..74e19170af8a 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -345,10 +345,24 @@  static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *fol
 	return MF_DELAYED;
 }
 
+#ifdef CONFIG_HAVE_KVM_GMEM_INVALIDATE
+static void kvm_gmem_free_folio(struct folio *folio)
+{
+	struct page *page = folio_page(folio, 0);
+	kvm_pfn_t pfn = page_to_pfn(page);
+	int order = folio_order(folio);
+
+	kvm_arch_gmem_invalidate(pfn, pfn + (1ul << order));
+}
+#endif
+
 static const struct address_space_operations kvm_gmem_aops = {
 	.dirty_folio = noop_dirty_folio,
 	.migrate_folio	= kvm_gmem_migrate_folio,
 	.error_remove_folio = kvm_gmem_error_folio,
+#ifdef CONFIG_HAVE_KVM_GMEM_INVALIDATE
+	.free_folio = kvm_gmem_free_folio,
+#endif
 };
 
 static int kvm_gmem_getattr(struct mnt_idmap *idmap, const struct path *path,