[PATCH v13 29/85] KVM: pfncache: Precisely track refcounted pages

Sean Christopherson
2024-10-10T18:57:50Z

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.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.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;