On Thu, Mar 10, 2022, Chao Peng wrote:
> Extend the memslot definition to provide fd-based private memory support
> by adding two new fields (private_fd/private_offset). The memslot then
> can maintain memory for both shared pages and private pages in a single
> memslot. Shared pages are provided by existing userspace_addr(hva) field
> and private pages are provided through the new private_fd/private_offset
> fields.
>
> Since there is no 'hva' concept anymore for private memory so we cannot
> rely on get_user_pages() to get a pfn, instead we use the newly added
> memfile_notifier to complete the same job.
>
> This new extension is indicated by a new flag KVM_MEM_PRIVATE.
>
> Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Needs a Co-developed-by: for Yu, or a From: if Yu is the sole author.
> Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> ---
> Documentation/virt/kvm/api.rst | 37 +++++++++++++++++++++++++++-------
> include/linux/kvm_host.h | 7 +++++++
> include/uapi/linux/kvm.h | 8 ++++++++
> 3 files changed, 45 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 3acbf4d263a5..f76ac598606c 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -1307,7 +1307,7 @@ yet and must be cleared on entry.
> :Capability: KVM_CAP_USER_MEMORY
> :Architectures: all
> :Type: vm ioctl
> -:Parameters: struct kvm_userspace_memory_region (in)
> +:Parameters: struct kvm_userspace_memory_region(_ext) (in)
> :Returns: 0 on success, -1 on error
>
> ::
> @@ -1320,9 +1320,17 @@ yet and must be cleared on entry.
> __u64 userspace_addr; /* start of the userspace allocated memory */
> };
>
> + struct kvm_userspace_memory_region_ext {
> + struct kvm_userspace_memory_region region;
> + __u64 private_offset;
> + __u32 private_fd;
> + __u32 padding[5];
Uber nit, I'd prefer we pad u32 for private_fd separate from padding the size of
the structure for future expansion.
Regarding future expansion, any reason not to go crazy and pad like 128+ bytes?
It'd be rather embarassing if the next memslot extension needs 3 u64s and we end
up with region_ext2 :-)
> +};
> +
> /* for kvm_memory_region::flags */
> #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
> #define KVM_MEM_READONLY (1UL << 1)
> + #define KVM_MEM_PRIVATE (1UL << 2)
>
> This ioctl allows the user to create, modify or delete a guest physical
> memory slot. Bits 0-15 of "slot" specify the slot id and this value
...
> +static inline bool kvm_slot_is_private(const struct kvm_memory_slot *slot)
I 100% think we should usurp the name "private" for these memslots, but as prep
work this series should first rename KVM_PRIVATE_MEM_SLOTS to avoid confusion.
Maybe KVM_INTERNAL_MEM_SLOTS?
