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KVM: pfncache: Precisely track refcounted pages

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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>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-30-seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-10-10 11:23:31 -07:00 committed by Paolo Bonzini
parent 775e3ff7bf
commit 3154ddcb6a
1 changed files with 7 additions and 4 deletions
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11
virt/kvm/pfncache.c
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@ -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;