On Tue, Feb 27, 2024 at 06:20:58PM -0500, Paolo Bonzini wrote:
> In order to be able to redo kvm_gmem_get_uninit_pfn, a hole must be punched
> into the filemap, thus allowing FGP_CREAT_ONLY to succeed again. This will
> be used whenever an operation that follows kvm_gmem_get_uninit_pfn fails.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 7 +++++++
> virt/kvm/guest_memfd.c | 28 ++++++++++++++++++++++++++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 03bf616b7308..192c58116220 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2436,6 +2436,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
> gfn_t gfn, kvm_pfn_t *pfn, int *max_order);
> int kvm_gmem_get_uninit_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
> gfn_t gfn, kvm_pfn_t *pfn, int *max_order);
> +int kvm_gmem_undo_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
> + gfn_t gfn, int order);
> #else
> static inline int kvm_gmem_get_pfn(struct kvm *kvm,
> struct kvm_memory_slot *slot, gfn_t gfn,
> @@ -2452,6 +2454,11 @@ static inline int kvm_gmem_get_uninit_pfn(struct kvm *kvm,
> KVM_BUG_ON(1, kvm);
> return -EIO;
> }
> +
> +static inline int kvm_gmem_undo_get_pfn(struct kvm *kvm,
> + struct kvm_memory_slot *slot, gfn_t gfn,
> + int order)
> +{}
return -EIO;
or compiler would complain that no return value.
> #endif /* CONFIG_KVM_PRIVATE_MEM */
>
> #ifdef CONFIG_HAVE_KVM_GMEM_PREPARE
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 7ec7afafc960..535ef1aa34fb 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -590,3 +590,31 @@ int kvm_gmem_get_uninit_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
> return __kvm_gmem_get_pfn(kvm, slot, gfn, pfn, max_order, false);
> }
> EXPORT_SYMBOL_GPL(kvm_gmem_get_uninit_pfn);
> +
> +int kvm_gmem_undo_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
> + gfn_t gfn, int order)
Didn't see the caller yet, but do we need to ensure the gfn is aligned
with page order? e.g.
WARN_ON(gfn & ((1UL << order) - 1));
> +{
> + pgoff_t index = gfn - slot->base_gfn + slot->gmem.pgoff;
> + struct kvm_gmem *gmem;
> + struct file *file;
> + int r;
> +
> + file = kvm_gmem_get_file(slot);
> + if (!file)
> + return -EFAULT;
> +
> + gmem = file->private_data;
> +
> + if (WARN_ON_ONCE(xa_load(&gmem->bindings, index) != slot)) {
> + r = -EIO;
> + goto out_fput;
> + }
> +
> + r = kvm_gmem_punch_hole(file_inode(file), index << PAGE_SHIFT, PAGE_SHIFT << order);
^
PAGE_SIZE << order
Thanks,
Yilun
> +
> +out_fput:
> + fput(file);
> +
> + return r;
> +}
> +EXPORT_SYMBOL_GPL(kvm_gmem_undo_get_pfn);
> --
> 2.39.0
>
>
>
