linux-kernel - [PATCH v12 27/84] KVM: pfncache: Precisely track refcounted pages

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Message-ID: <20240726235234.228822-28-seanjc@google.com>
Date: Fri, 26 Jul 2024 16:51:36 -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 27/84] KVM: pfncache: Precisely track refcounted pages

Track refcounted struct page memory using kvm_follow_pfn.refcounted_page
instead of relying on kvm_release_pfn_clean() to correctly detect that the
pfn is associated with a struct page.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 virt/kvm/pfncache.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 067daf9ad6ef..728d2c1b488a 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -159,11 +159,14 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 	kvm_pfn_t new_pfn = KVM_PFN_ERR_FAULT;
 	void *new_khva = NULL;
 	unsigned long mmu_seq;
+	struct page *page;
+
 	struct kvm_follow_pfn kfp = {
 		.slot = gpc->memslot,
 		.gfn = gpa_to_gfn(gpc->gpa),
 		.flags = FOLL_WRITE,
 		.hva = gpc->uhva,
+		.refcounted_page = &page,
 	};
 
 	lockdep_assert_held(&gpc->refresh_lock);
@@ -198,7 +201,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 			if (new_khva != old_khva)
 				gpc_unmap(new_pfn, new_khva);
 
-			kvm_release_pfn_clean(new_pfn);
+			kvm_release_page_unused(page);
 
 			cond_resched();
 		}
@@ -218,7 +221,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 			new_khva = gpc_map(new_pfn);
 
 		if (!new_khva) {
-			kvm_release_pfn_clean(new_pfn);
+			kvm_release_page_unused(page);
 			goto out_error;
 		}
 
@@ -236,11 +239,11 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 	gpc->khva = new_khva + offset_in_page(gpc->uhva);
 
 	/*
-	 * Put the reference to the _new_ pfn.  The pfn is now tracked by the
+	 * Put the reference to the _new_ page.  The page is now tracked by the
 	 * cache and can be safely migrated, swapped, etc... as the cache will
 	 * invalidate any mappings in response to relevant mmu_notifier events.
 	 */
-	kvm_release_pfn_clean(new_pfn);
+	kvm_release_page_clean(page);
 
 	return 0;
 
-- 
2.46.0.rc1.232.g9752f9e123-goog