[PATCH 01/12] KVM: guest_memfd: return folio from __kvm_gmem_get_pfn()

Paolo Bonzini
2024-07-11T22:28:02Z

Right now this is simply more consistent and avoids use of pfn_to_page()
and put_page(). It will be put to more use in upcoming patches, to
ensure that the up-to-date flag is set at the very end of both the
kvm_gmem_get_pfn() and kvm_gmem_populate() flows.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
virt/kvm/guest_memfd.c | 37 ++++++++++++++++++++-----------------
1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 1c509c351261..522e1b28e7ae 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -541,34 +541,34 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot)
fput(file);
}

-static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
- gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prepare)
+static struct folio *
+__kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
+ gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prepare)
{
pgoff_t index = gfn - slot->base_gfn + slot->gmem.pgoff;
struct kvm_gmem *gmem = file->private_data;
struct folio *folio;
struct page *page;
- int r;

if (file != slot->gmem.file) {
WARN_ON_ONCE(slot->gmem.file);
- return -EFAULT;
+ return ERR_PTR(-EFAULT);
}

gmem = file->private_data;
if (xa_load(&gmem->bindings, index) != slot) {
WARN_ON_ONCE(xa_load(&gmem->bindings, index));
- return -EIO;
+ return ERR_PTR(-EIO);
}

folio = kvm_gmem_get_folio(file_inode(file), index, prepare);
if (IS_ERR(folio))
- return PTR_ERR(folio);
+ return folio;

if (folio_test_hwpoison(folio)) {
folio_unlock(folio);
folio_put(folio);
- return -EHWPOISON;
+ return ERR_PTR(-EHWPOISON);
}

page = folio_file_page(folio, index);
@@ -577,25 +577,25 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
if (max_order)
*max_order = 0;

- r = 0;
-
folio_unlock(folio);
-
- return r;
+ return folio;
}

int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
gfn_t gfn, kvm_pfn_t *pfn, int *max_order)
{
struct file *file = kvm_gmem_get_file(slot);
- int r;
+ struct folio *folio;

if (!file)
return -EFAULT;

- r = __kvm_gmem_get_pfn(file, slot, gfn, pfn, max_order, true);
+ folio = __kvm_gmem_get_pfn(file, slot, gfn, pfn, max_order, true);
fput(file);
- return r;
+ if (IS_ERR(folio))
+ return PTR_ERR(folio);
+
+ return 0;
}
EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);

@@ -625,6 +625,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long

npages = min_t(ulong, slot->npages - (start_gfn - slot->base_gfn), npages);
for (i = 0; i < npages; i += (1 << max_order)) {
+ struct folio *folio;
gfn_t gfn = start_gfn + i;
kvm_pfn_t pfn;

@@ -633,9 +634,11 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
break;
}

- ret = __kvm_gmem_get_pfn(file, slot, gfn, &pfn, &max_order, false);
- if (ret)
+ folio = __kvm_gmem_get_pfn(file, slot, gfn, &pfn, &max_order, false);
+ if (IS_ERR(folio)) {
+ ret = PTR_ERR(folio);
break;
+ }

if (!IS_ALIGNED(gfn, (1 << max_order)) ||
(npages - i) < (1 << max_order))
@@ -644,7 +647,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
p = src ? src + i * PAGE_SIZE : NULL;
ret = post_populate(kvm, gfn, pfn, p, max_order, opaque);

- put_page(pfn_to_page(pfn));
+ folio_put(folio);
if (ret)
break;
}
--
2.43.0