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@redhat.com>
---
virt/kvm/guest_memfd.c | 38 +++++++++++++++++++++++---------------
1 file changed, 23 insertions(+), 15 deletions(-)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 486748e65f36..a537a7e63ab5 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -540,33 +540,29 @@ 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 (!folio) {
- r = -ENOMEM;
- goto out_fput;
- }
+ if (!folio)
+ return -ENOMEM;
if (folio_test_hwpoison(folio)) {
r = -EHWPOISON;
@@ -583,9 +579,21 @@ 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);
--
2.43.0On Thu, Apr 04, 2024, Paolo Bonzini wrote: > 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@redhat.com> > --- > virt/kvm/guest_memfd.c | 38 +++++++++++++++++++++++--------------- > 1 file changed, 23 insertions(+), 15 deletions(-) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 486748e65f36..a537a7e63ab5 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -540,33 +540,29 @@ 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) I genuinely don't know what it means to "prepare" a guest_memfd. I see it becomes if (!prepare) fgp_flags |= FGP_CREAT_ONLY; but I find the name "prepare" to be extremely unhelpful.
On Wed, Apr 24, 2024, Sean Christopherson wrote:
> On Thu, Apr 04, 2024, Paolo Bonzini wrote:
> > 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@redhat.com>
> > ---
> > virt/kvm/guest_memfd.c | 38 +++++++++++++++++++++++---------------
> > 1 file changed, 23 insertions(+), 15 deletions(-)
> >
> > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> > index 486748e65f36..a537a7e63ab5 100644
> > --- a/virt/kvm/guest_memfd.c
> > +++ b/virt/kvm/guest_memfd.c
> > @@ -540,33 +540,29 @@ 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)
>
> I genuinely don't know what it means to "prepare" a guest_memfd. I see it becomes
>
> if (!prepare)
> fgp_flags |= FGP_CREAT_ONLY;
>
> but I find the name "prepare" to be extremely unhelpful.
Ah, I'm blind. Maybe "do_prepare", or "do_arch_prepare"? To make it clear that
it's a command, not a description of the operation (which is how I first read it).
And I feel like overloading it to also mean FGP_CREAT_ONLY when _not_ preparing
the memory is odd.
if (prepare) {
int r = kvm_gmem_prepare_folio(inode, index, folio);
if (r < 0) {
folio_unlock(folio);
folio_put(folio);
return ERR_PTR(r);
}
}
Instead of "prepare" as a command, would it make sense to describe the "populating"
case? Because I think it's more intuitive that populating _needs_ to operate on
new, unprepared data.
On Thu, Apr 04, 2024 at 02:50:29PM -0400, Paolo Bonzini wrote:
> 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@redhat.com>
> ---
> virt/kvm/guest_memfd.c | 38 +++++++++++++++++++++++---------------
> 1 file changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 486748e65f36..a537a7e63ab5 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -540,33 +540,29 @@ 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);
This should be:
folio = kvm_gmem_get_folio(file_inode(file), index, prepare);
Otherwise:
Reviewed-by: Michael Roth <michael.roth@amd.com>
-Mike
> - if (!folio) {
> - r = -ENOMEM;
> - goto out_fput;
> - }
> + if (!folio)
> + return -ENOMEM;
>
> if (folio_test_hwpoison(folio)) {
> r = -EHWPOISON;
> @@ -583,9 +579,21 @@ 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
>
>
© 2016 - 2026 Red Hat, Inc.