[PATCH v2 4/9] KVM: Rework .gmem_invalidate() into .gmem_free_folio()

[Sean Christopherson <seanjc@google.com>]

Rename .gmem_invalidate() to .gmem_free_folio() as the hook is called when
a folio is freed, which is far too late and lack sufficient information for
KVM to actually invalidate its usage of the memory.  Drop guest_memfd's
trampoline and just wire up .free_folio() directly to the arch callback so
that the chain of events is clear and obvious.

Opportunistically guard kvm_x86_ops.gmem_free_folio with an ifdef to
ensure the callback will actually be called, e.g. so that non-SEV code
doesn't try to wire up a callback without enabling
CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE.

No functional change intended.

Cc: stable@vger.kernel.org # 6.12.x
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/include/asm/kvm-x86-ops.h |  4 +++-
 arch/x86/include/asm/kvm_host.h    |  4 +++-
 arch/x86/kvm/svm/sev.c             |  4 +++-
 arch/x86/kvm/svm/svm.c             |  4 +++-
 arch/x86/kvm/svm/svm.h             |  3 +--
 arch/x86/kvm/x86.c                 |  4 ++--
 include/linux/kvm_host.h           |  2 +-
 virt/kvm/guest_memfd.c             | 13 +------------
 8 files changed, 17 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 83dc5086138b..e36eba952705 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -147,7 +147,9 @@ KVM_X86_OP_OPTIONAL(get_untagged_addr)
 KVM_X86_OP_OPTIONAL(alloc_apic_backing_page)
 KVM_X86_OP_OPTIONAL_RET0(gmem_prepare)
 KVM_X86_OP_OPTIONAL_RET0(gmem_max_mapping_level)
-KVM_X86_OP_OPTIONAL(gmem_invalidate)
+#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
+KVM_X86_OP_OPTIONAL(gmem_free_folio)
+#endif
 #endif
 
 #undef KVM_X86_OP
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b517257a6315..dd542c7a7376 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1901,7 +1901,9 @@ struct kvm_x86_ops {
 	gva_t (*get_untagged_addr)(struct kvm_vcpu *vcpu, gva_t gva, unsigned int flags);
 	void *(*alloc_apic_backing_page)(struct kvm_vcpu *vcpu);
 	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);
+#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
+	void (*gmem_free_folio)(struct folio *folio);
+#endif
 	int (*gmem_max_mapping_level)(struct kvm *kvm, kvm_pfn_t pfn, bool is_private);
 };
 
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 30792adcfc8e..3d90aa723dc2 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -5136,8 +5136,10 @@ int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order)
 	return 0;
 }
 
-void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
+void sev_gmem_free_folio(struct folio *folio)
 {
+	kvm_pfn_t start = page_to_pfn(folio_page(folio, 0));
+	kvm_pfn_t end = start + (1ul << folio_order(folio));
 	kvm_pfn_t pfn;
 
 	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ef69a51ab27f..6f1823e820a4 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5460,9 +5460,11 @@ 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,
 
+#ifdef CONFIG_KVM_AMD_SEV
 	.gmem_prepare = sev_gmem_prepare,
-	.gmem_invalidate = sev_gmem_invalidate,
+	.gmem_free_folio = sev_gmem_free_folio,
 	.gmem_max_mapping_level = sev_gmem_max_mapping_level,
+#endif
 };
 
 /*
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index d077783c287e..2f8215810a08 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -1009,7 +1009,7 @@ int sev_dev_get_attr(u32 group, u64 attr, u64 *val);
 extern unsigned int max_sev_asid;
 void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code);
 int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order);
-void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end);
+void sev_gmem_free_folio(struct folio *folio);
 int sev_gmem_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, bool is_private);
 struct vmcb_save_area *sev_decrypt_vmsa(struct kvm_vcpu *vcpu);
 void sev_free_decrypted_vmsa(struct kvm_vcpu *vcpu, struct vmcb_save_area *vmsa);
@@ -1039,7 +1039,6 @@ static inline int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, in
 {
 	return 0;
 }
-static inline void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end) {}
 static inline int sev_gmem_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, bool is_private)
 {
 	return 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0626e835e9eb..adc1e1b244c7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10592,9 +10592,9 @@ int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_ord
 #endif
 
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
-void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
+void kvm_arch_gmem_free_folio(struct folio *folio)
 {
-	kvm_x86_call(gmem_invalidate)(start, end);
+	kvm_x86_call(gmem_free_folio)(folio);
 }
 #endif
 #endif
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ab8cfaec82d3..e5b47a5e4cea 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2607,7 +2607,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src,
 #endif
 
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
-void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end);
+void kvm_arch_gmem_free_folio(struct folio *folio);
 #endif
 
 #ifdef CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 86690683b2fe..1618acc3ca64 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -523,23 +523,12 @@ static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *fol
 	return MF_DELAYED;
 }
 
-#ifdef CONFIG_HAVE_KVM_ARCH_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_ARCH_GMEM_INVALIDATE
-	.free_folio = kvm_gmem_free_folio,
+	.free_folio = kvm_arch_gmem_free_folio,
 #endif
 };
 
-- 
2.55.0.rc0.799.gd6f94ed593-goog