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KVM: guest_memfd: Pass index, not gfn, to __kvm_gmem_get_pfn()

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Refactor guest_memfd usage of __kvm_gmem_get_pfn() to pass the index into
the guest_memfd file instead of the gfn, i.e. resolve the index based on
the slot+gfn in the caller instead of in __kvm_gmem_get_pfn().  This will
allow kvm_gmem_get_pfn() to retrieve and return the specific "struct page",
which requires the index into the folio, without a redoing the index
calculation multiple times (which isn't costly, just hard to follow).

Opportunistically add a kvm_gmem_get_index() helper to make the copy+pasted
code easier to understand.

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: <20241010182427.1434605-46-seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-10-10 11:23:47 -07:00 committed by Paolo Bonzini
parent 54ba8c98a2
commit 4af18dc6a9
1 changed files with 13 additions and 7 deletions
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20
virt/kvm/guest_memfd.c
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@ -302,6 +302,11 @@ static inline struct file *kvm_gmem_get_file(struct kvm_memory_slot *slot)
return get_file_active(&slot->gmem.file);
}
static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn)
{
return gfn - slot->base_gfn + slot->gmem.pgoff;
}
static struct file_operations kvm_gmem_fops = {
.open = generic_file_open,
.release = kvm_gmem_release,
@ -551,12 +556,11 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot)
}
/* Returns a locked folio on success. */
static struct folio *
__kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
gfn_t gfn, kvm_pfn_t *pfn, bool *is_prepared,
int *max_order)
static struct folio *__kvm_gmem_get_pfn(struct file *file,
struct kvm_memory_slot *slot,
pgoff_t index, kvm_pfn_t *pfn,
bool *is_prepared, int *max_order)
{
pgoff_t index = gfn - slot->base_gfn + slot->gmem.pgoff;
struct kvm_gmem *gmem = file->private_data;
struct folio *folio;
@ -592,6 +596,7 @@ __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
gfn_t gfn, kvm_pfn_t *pfn, int *max_order)
{
pgoff_t index = kvm_gmem_get_index(slot, gfn);
struct file *file = kvm_gmem_get_file(slot);
struct folio *folio;
bool is_prepared = false;
@ -600,7 +605,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
if (!file)
return -EFAULT;
folio = __kvm_gmem_get_pfn(file, slot, gfn, pfn, &is_prepared, max_order);
folio = __kvm_gmem_get_pfn(file, slot, index, pfn, &is_prepared, max_order);
if (IS_ERR(folio)) {
r = PTR_ERR(folio);
goto out;
@ -648,6 +653,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
for (i = 0; i < npages; i += (1 << max_order)) {
struct folio *folio;
gfn_t gfn = start_gfn + i;
pgoff_t index = kvm_gmem_get_index(slot, gfn);
bool is_prepared = false;
kvm_pfn_t pfn;
@ -656,7 +662,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
break;
}
folio = __kvm_gmem_get_pfn(file, slot, gfn, &pfn, &is_prepared, &max_order);
folio = __kvm_gmem_get_pfn(file, slot, index, &pfn, &is_prepared, &max_order);
if (IS_ERR(folio)) {
ret = PTR_ERR(folio);
break;