[PATCH 03/12] KVM: guest_memfd: do not go through struct page

Paolo Bonzini
2024-07-11T22:28:04Z

We have a perfectly usable folio, use it to retrieve the pfn and order.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
virt/kvm/guest_memfd.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 1ea632dbae57..5221b584288f 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -13,6 +13,18 @@ struct kvm_gmem {
struct list_head entry;
};

+/**
+ * folio_file_pfn - like folio_file_page, but return a pfn.
+ * @folio: The folio which contains this index.
+ * @index: The index we want to look up.
+ *
+ * Return: The pfn for this index.
+ */
+static inline kvm_pfn_t folio_file_pfn(struct folio *folio, pgoff_t index)
+{
+ return folio_pfn(folio) + (index & (folio_nr_pages(folio) - 1));
+}
+
static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio)
{
#ifdef CONFIG_HAVE_KVM_GMEM_PREPARE
@@ -22,7 +34,6 @@ static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct fol
list_for_each_entry(gmem, gmem_list, entry) {
struct kvm_memory_slot *slot;
struct kvm *kvm = gmem->kvm;
- struct page *page;
kvm_pfn_t pfn;
gfn_t gfn;
int rc;
@@ -34,13 +45,12 @@ static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct fol
if (!slot)
continue;

- page = folio_file_page(folio, index);
- pfn = page_to_pfn(page);
+ pfn = folio_file_pfn(folio, index);
gfn = slot->base_gfn + index - slot->gmem.pgoff;
- rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, compound_order(compound_head(page)));
+ rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, folio_order(folio));
if (rc) {
- pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx GFN %llx PFN %llx error %d.\n",
- index, gfn, pfn, rc);
+ pr_warn_ratelimited("gmem: Failed to prepare folio for GFN %llx PFN %llx error %d.\n",
+ gfn, pfn, rc);
return rc;
}
}
@@ -548,7 +558,6 @@ __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
pgoff_t index = gfn - slot->base_gfn + slot->gmem.pgoff;
struct kvm_gmem *gmem = file->private_data;
struct folio *folio;
- struct page *page;

if (file != slot->gmem.file) {
WARN_ON_ONCE(slot->gmem.file);
@@ -571,9 +580,7 @@ __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
return ERR_PTR(-EHWPOISON);
}

- page = folio_file_page(folio, index);
-
- *pfn = page_to_pfn(page);
+ *pfn = folio_file_pfn(folio, index);
if (max_order)
*max_order = 0;

--
2.43.0