On 19/03/2019 15:04, Suraj Jitindar Singh wrote:
> Implement the function kvmppc_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>
> ---
> arch/powerpc/kvm/book3s_hv.c | 69 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 69 insertions(+)
>
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index ec38576dc685..7179ea783f4f 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -814,6 +814,75 @@ static int kvmppc_h_set_mode(struct kvm_vcpu *vcpu, unsigned long mflags,
> }
> }
>
> +static int __kvmppc_copy_guest_page(struct kvm_memory_slot *to_memslot,
> + gfn_t to_gfn, int to_offset,
> + struct kvm_memory_slot *from_memslot,
> + gfn_t from_gfn, int from_offset, int len)
> +{
> + int r;
> + unsigned long to_addr, from_addr;
> +
> + to_addr = gfn_to_hva_memslot(to_memslot, to_gfn);
> + if (kvm_is_error_hva(to_addr))
> + return -EFAULT;
> + from_addr = gfn_to_hva_memslot(from_memslot, from_gfn);
> + if (kvm_is_error_hva(from_addr))
> + return -EFAULT;
> + r = raw_copy_in_user((void __user *)to_addr + to_offset,
> + (void __user *)from_addr + from_offset, len);
> + if (r)
> + return -EFAULT;
> + return 0;
> +}
> +
> +static int next_segment_many(unsigned long len, int offset1, int offset2)
What is the "_many" suffix about?
> +{
> + int size = min(PAGE_SIZE - offset1, PAGE_SIZE - offset2);
Nitpicking :) Here it is min()...
> +
> + if (len > size)
> + return size;
> + else
> + return len;
...but here it is if() when it could also be min() (or may be min_t()).
> +}
> +
> +static int kvmppc_copy_guest(struct kvm *kvm, gpa_t to, gpa_t from,
> + unsigned long len)
This does not compile (most comments are made just because I had to
reply anyway):
/home/aik/p/kernel/arch/powerpc/kvm/book3s_hv.c:835:12: error:
‘kvmppc_copy_guest’ defined but not used [-Werror=unused-function]
static int kvmppc_copy_guest(struct kvm *kvm, gpa_t to, gpa_t from,
^~~~~~~~~~~~~~~~~
imho 1/3 and 2/3 should be one patch.
A general comment is that the H_PAGE_INIT hcall description says "The
logical addresses ... must both point to the start of a 4 K system
memory page" so the loop will never have to execute more than once,
cannot span memslots => it could be lot simpler then, or I missed
something here (unlikely, after reading 3/3).
> +{
> + 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 = __kvmppc_copy_guest_page(to_memslot, to_gfn, to_offset,
> + from_memslot, from_gfn,
> + from_offset, seg);
> + if (ret < 0)
> + return ret;
> + mark_page_dirty(kvm, to_gfn);
Nit: if you made mark_page_dirty_in_slot() public (yeah it is in the
common code), you could save here one search through memslots.
> +
> + to_offset = (to_offset + seg) & (PAGE_SIZE - 1);
s/(PAGE_SIZE - 1)/~PAGE_MASK/ ? Or even use again that offset_in_page()
as you did above?
> + from_offset = (from_offset + seg) & (PAGE_SIZE - 1);
> + len -= seg;
> + if (!to_offset)
> + to_gfn += 1;
> + if (!from_offset)
> + from_gfn += 1;
> + }
> + return 0;
> +}
> +
> static int kvm_arch_vcpu_yield_to(struct kvm_vcpu *target)
> {
> struct kvmppc_vcore *vcore = target->arch.vcore;
>
--
Alexey
