[PATCH 6/9] KVM: guest_memfd: extract __kvm_gmem_get_pfn()

From: Paolo Bonzini
Date: Tue May 07 2024 - 14:09:41 EST


In preparation for adding a function that walks a set of pages
provided by userspace and populates them in a guest_memfd,
add a version of kvm_gmem_get_pfn() that has a "bool prepare"
argument and passes it down to kvm_gmem_get_folio().

Populating guest memory has to call repeatedly __kvm_gmem_get_pfn()
on the same file, so make the new function take struct file*.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
virt/kvm/guest_memfd.c | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 0176089be731..bfe437098b79 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -528,33 +528,29 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot)
fput(file);
}

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

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

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

- folio = kvm_gmem_get_folio(file_inode(file), index, true);
- if (IS_ERR(folio)) {
- r = PTR_ERR(folio);
- goto out_fput;
- }
+ folio = kvm_gmem_get_folio(file_inode(file), index, prepare);
+ if (IS_ERR(folio))
+ return PTR_ERR(folio);

if (folio_test_hwpoison(folio)) {
r = -EHWPOISON;
@@ -571,9 +567,21 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,

out_unlock:
folio_unlock(folio);
-out_fput:
- fput(file);

return r;
}
+
+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;
+
+ if (!file)
+ return -EFAULT;
+
+ r = __kvm_gmem_get_pfn(file, slot, gfn, pfn, max_order, true);
+ fput(file);
+ return r;
+}
EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
--
2.43.0