On Wed, Apr 12, 2023 at 09:34:55PM +0000, Anish Moorthy wrote:
> Implement KVM_CAP_MEMORY_FAULT_INFO for efaults from
> kvm_vcpu_write_guest_page()
>
> Signed-off-by: Anish Moorthy <amoorthy@xxxxxxxxxx>
> ---
> virt/kvm/kvm_main.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 63b4285d858d1..b29a38af543f0 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3119,8 +3119,11 @@ int kvm_vcpu_write_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn,
> const void *data, int offset, int len)
> {
> struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
> + int ret = __kvm_write_guest_page(vcpu->kvm, slot, gfn, data, offset, len);
>
> - return __kvm_write_guest_page(vcpu->kvm, slot, gfn, data, offset, len);
> + if (ret == -EFAULT)
> + kvm_populate_efault_info(vcpu, gfn * PAGE_SIZE + offset, len);
> + return ret;
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest_page);
Why need to trap this? Is this -EFAULT part of the "scalable userfault"
plan or not?
My previous memory was one can still leave things like copy_to_user() to go
via the userfaults channels which should work in parallel with the new vcpu
MEMORY_FAULT exit. But maybe the plan changed?
Thanks,
--
Peter Xu
