On Wed, 2019-03-06 at 09:21 -0800, Sean Christopherson wrote:
> On Wed, Mar 06, 2019 at 05:00:15PM +1100, Suraj Jitindar Singh wrote:
> > Implement the function kvm_copy_guest() to be used to perform a
> > memory
> > copy from one guest physical address to another of a variable
> > length.
> >
> > This performs similar functionality as the kvm_read_guest() and
> > kvm_write_guest() functions, except both addresses point to guest
> > memory.
> > This performs a copy in place using raw_copy_in_user() to avoid
> > having to
> > buffer the data.
> >
> > The guest memory can reside in different memslots and the copy
> > length
> > can span memslots.
> >
> > Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> >
> > ---
> >
> > I suspect additional checking may be required around the
> > raw_copy_in_user()
> > call.
> >
> > ---
> > include/linux/kvm_host.h | 1 +
> > virt/kvm/kvm_main.c | 69
> > ++++++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 70 insertions(+)
> >
>
> ...
>
> > +static int next_segment_many(unsigned long len, int offset1, int
> > offset2)
> > +{
> > + int size = min(PAGE_SIZE - offset1, PAGE_SIZE - offset2);
> > +
> > + if (len > size)
> > + return size;
> > + else
> > + return len;
> > +}
> > +
> > +int kvm_copy_guest(struct kvm *kvm, gpa_t to, gpa_t from, unsigned
> > long len)
> > +{
> > + struct kvm_memory_slot *to_memslot = NULL;
> > + struct kvm_memory_slot *from_memslot = NULL;
> > + gfn_t to_gfn = to >> PAGE_SHIFT;
> > + gfn_t from_gfn = from >> PAGE_SHIFT;
> > + int seg;
> > + int to_offset = offset_in_page(to);
> > + int from_offset = offset_in_page(from);
> > + int ret;
> > +
> > + while ((seg = next_segment_many(len, to_offset,
> > from_offset)) != 0) {
> > + if (!to_memslot || (to_gfn >= (to_memslot-
> > >base_gfn +
> > + to_memslot-
> > >npages)))
> > + to_memslot = gfn_to_memslot(kvm, to_gfn);
> > + if (!from_memslot || (from_gfn >= (from_memslot-
> > >base_gfn +
> > + from_memslot-
> > >npages)))
> > + from_memslot = gfn_to_memslot(kvm,
> > from_gfn);
> > +
> > + ret = __kvm_copy_guest_page(to_memslot, to_gfn,
> > to_offset,
> > + from_memslot,
> > from_gfn, from_offset,
> > + seg);
> > + if (ret < 0)
> > + return ret;
> > +
> > + to_offset = (to_offset + seg) & (PAGE_SIZE - 1);
> > + from_offset = (from_offset + seg) & (PAGE_SIZE -
> > 1);
> > + len -= seg;
> > + if (!to_offset)
> > + to_gfn += 1;
> > + if (!from_offset)
> > + from_gfn += 1;
> > + }
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(kvm_copy_guest);
>
> Is there a need to support spanning multiple pages at this
> time? Your use
> case always accesses exactly a page and requires both dst and src to
> be
> page aligned. I.e. provide just kvm_copy_guest_page() for
> simplicity.
There is no need for multiple pages at this stage. However I wanted to
match kvm_[read/write]_guest which allow multiple pages and there
didn't seem any reason to not just implement it this way from the
start.
>
> > +
> > static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots,
> > struct gfn_to_hva_cache
> > *ghc,
> > gpa_t gpa, unsigned long
> > len)
> > --
> > 2.13.6
> >
