linux-kernel - [RFC PATCH v5 19/45] KVM: Allow owner of kvm_mmu_memory

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Message-ID: <20260129011517.3545883-20-seanjc@google.com>
Date: Wed, 28 Jan 2026 17:14:51 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Thomas Gleixner <tglx@...nel.org>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Kiryl Shutsemau <kas@...nel.org>, Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev, 
	kvm@...r.kernel.org, Kai Huang <kai.huang@...el.com>, 
	Rick Edgecombe <rick.p.edgecombe@...el.com>, Yan Zhao <yan.y.zhao@...el.com>, 
	Vishal Annapurve <vannapurve@...gle.com>, Ackerley Tng <ackerleytng@...gle.com>, 
	Sagi Shahar <sagis@...gle.com>, Binbin Wu <binbin.wu@...ux.intel.com>, 
	Xiaoyao Li <xiaoyao.li@...el.com>, Isaku Yamahata <isaku.yamahata@...el.com>
Subject: [RFC PATCH v5 19/45] KVM: Allow owner of kvm_mmu_memory_cache to
 provide a custom page allocator

Extend "struct kvm_mmu_memory_cache" to support a custom page allocator
so that x86's TDX can update per-page metadata on allocation and free().

Name the allocator page_get() to align with __get_free_page(), e.g. to
communicate that it returns an "unsigned long", not a "struct page", and
to avoid collisions with macros, e.g. with alloc_page.

Suggested-by: Kai Huang <kai.huang@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 include/linux/kvm_types.h | 2 ++
 virt/kvm/kvm_main.c       | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index a568d8e6f4e8..87fa9deffdb7 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -112,6 +112,8 @@ struct kvm_mmu_memory_cache {
 	gfp_t gfp_custom;
 	u64 init_value;
 	struct kmem_cache *kmem_cache;
+	unsigned long (*page_get)(gfp_t gfp);
+	void (*page_free)(unsigned long addr);
 	int capacity;
 	int nobjs;
 	void **objects;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 571cf0d6ec01..7015edce5bd8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -356,7 +356,10 @@ static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
 	if (mc->kmem_cache)
 		return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
 
-	page = (void *)__get_free_page(gfp_flags);
+	if (mc->page_get)
+		page = (void *)mc->page_get(gfp_flags);
+	else
+		page = (void *)__get_free_page(gfp_flags);
 	if (page && mc->init_value)
 		memset64(page, mc->init_value, PAGE_SIZE / sizeof(u64));
 	return page;
@@ -416,6 +419,8 @@ void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
 	while (mc->nobjs) {
 		if (mc->kmem_cache)
 			kmem_cache_free(mc->kmem_cache, mc->objects[--mc->nobjs]);
+		else if (mc->page_free)
+			mc->page_free((unsigned long)mc->objects[--mc->nobjs]);
 		else
 			free_page((unsigned long)mc->objects[--mc->nobjs]);
 	}
-- 
2.53.0.rc1.217.geba53bf80e-goog