On Mon, Mar 28, 2022 at 09:27:32PM +0000, Sean Christopherson wrote:
> 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.
Yes a Co-developed-by for Yu is needed, for all the patches throught the series.
>
> > 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 :-)
OK, so maybe:
__u64 private_offset;
__u32 private_fd;
__u32 pad1;
__u32 pad2[28];
>
> > +};
> > +
> > /* 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?
Oh, I didn't realized 'PRIVATE' is already taken. KVM_INTERNAL_MEM_SLOTS
sounds good.
Thanks,
Chao
