Re: [PATCH 1/4] KVM: guest_memfd: add generic post_populate callback

[Nikita Kalyazin]

On 22/11/2024 18:40, Mike Day wrote:
> On 10/24/24 04:54, Nikita Kalyazin wrote:
> > This adds a generic implementation of the `post_populate` callback for
> > the `kvm_gmem_populate`.  The only thing it does is populates the pages
> > with data provided by userspace if the user pointer is not NULL,
> > otherwise it clears the pages.
> > This is supposed to be used by KVM_X86_SW_PROTECTED_VM VMs.
> >
> > Signed-off-by: Nikita Kalyazin <kalyazin@xxxxxxxxxx>
> > ---
> >   virt/kvm/guest_memfd.c | 21 +++++++++++++++++++++
> >   1 file changed, 21 insertions(+)
> >
> > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> > index 8f079a61a56d..954312fac462 100644
> > --- a/virt/kvm/guest_memfd.c
> > +++ b/virt/kvm/guest_memfd.c
> > @@ -620,6 +620,27 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct 
> > kvm_memory_slot *slot,
> >   EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
> >
> >   #ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
>
> KVM_AMD_SEV can select KVM_GENERIC_PRIVATE_MEM, so to guarantee this is 
> only for
> software protection it might be good to use:
>
> #if defined CONFIG_KVM_GENERIC_PRIVATE_MEM && !defined CONFIG_KVM_AMD_SEV
>
> That could end up too verbose so there should probably be some more 
> concise mechanism
> to guarantee this generic callback isn't used for a hardware-protected 
> guest.

Thanks, will make a note for myself for the next iteration.

> Mike