linux-kernel - [PATCH v12 28/84] KVM: Migrate kvm_vcpu_map() to kvm_follow

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Message-ID: <20240726235234.228822-29-seanjc@google.com>
Date: Fri, 26 Jul 2024 16:51:37 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Tianrui Zhao <zhaotianrui@...ngson.cn>, 
	Bibo Mao <maobibo@...ngson.cn>, Huacai Chen <chenhuacai@...nel.org>, 
	Michael Ellerman <mpe@...erman.id.au>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, 
	Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, loongarch@...ts.linux.dev, linux-mips@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	David Matlack <dmatlack@...gle.com>, David Stevens <stevensd@...omium.org>
Subject: [PATCH v12 28/84] KVM: Migrate kvm_vcpu_map() to kvm_follow_pfn()

From: David Stevens <stevensd@...omium.org>

Migrate kvm_vcpu_map() to kvm_follow_pfn(), and have it track whether or
not the map holds a refcounted struct page.  Precisely tracking struct
page references will eventually allow removing kvm_pfn_to_refcounted_page()
and its various wrappers.

Signed-off-by: David Stevens <stevensd@...omium.org>
[sean: use a pointer instead of a boolean]
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 include/linux/kvm_host.h |  2 +-
 virt/kvm/kvm_main.c      | 26 ++++++++++++++++----------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a5dcb72bab00..8b5ac3305b05 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -280,6 +280,7 @@ struct kvm_host_map {
 	 * can be used as guest memory but they are not managed by host
 	 * kernel).
 	 */
+	struct page *refcounted_page;
 	struct page *page;
 	void *hva;
 	kvm_pfn_t pfn;
@@ -1223,7 +1224,6 @@ void kvm_release_pfn_dirty(kvm_pfn_t pfn);
 void kvm_set_pfn_dirty(kvm_pfn_t pfn);
 void kvm_set_pfn_accessed(kvm_pfn_t pfn);
 
-void kvm_release_pfn(kvm_pfn_t pfn, bool dirty);
 int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
 			int len);
 int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 48b626f1b5f3..255cbed83b40 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3113,21 +3113,21 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_page);
 
-void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
-{
-	if (dirty)
-		kvm_release_pfn_dirty(pfn);
-	else
-		kvm_release_pfn_clean(pfn);
-}
-
 int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
 {
+	struct kvm_follow_pfn kfp = {
+		.slot = gfn_to_memslot(vcpu->kvm, gfn),
+		.gfn = gfn,
+		.flags = FOLL_WRITE,
+		.refcounted_page = &map->refcounted_page,
+	};
+
+	map->refcounted_page = NULL;
 	map->page = NULL;
 	map->hva = NULL;
 	map->gfn = gfn;
 
-	map->pfn = gfn_to_pfn(vcpu->kvm, gfn);
+	map->pfn = kvm_follow_pfn(&kfp);
 	if (is_error_noslot_pfn(map->pfn))
 		return -EINVAL;
 
@@ -3159,10 +3159,16 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
 	if (dirty)
 		kvm_vcpu_mark_page_dirty(vcpu, map->gfn);
 
-	kvm_release_pfn(map->pfn, dirty);
+	if (map->refcounted_page) {
+		if (dirty)
+			kvm_release_page_dirty(map->refcounted_page);
+		else
+			kvm_release_page_clean(map->refcounted_page);
+	}
 
 	map->hva = NULL;
 	map->page = NULL;
+	map->refcounted_page = NULL;
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);
 
-- 
2.46.0.rc1.232.g9752f9e123-goog