On Fri, Apr 19, 2024 at 06:12:11PM +0200, Paolo Bonzini wrote:
> On Fri, Apr 19, 2024 at 1:56 PM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> > > + ret = kvm_gmem_populate(kvm, params.gfn_start, u64_to_user_ptr(params.uaddr),
> > > + npages, sev_gmem_post_populate, &sev_populate_args);
> > > + if (ret < 0) {
> > > + argp->error = sev_populate_args.fw_error;
> > > + pr_debug("%s: kvm_gmem_populate failed, ret %d (fw_error %d)\n",
> > > + __func__, ret, argp->error);
> > > + } else if (ret < npages) {
> > > + params.len = ret * PAGE_SIZE;
> > > + ret = -EINTR;
> >
> > This probably should 1) update also gfn_start and uaddr 2) return 0
> > for consistency with the planned KVM_PRE_FAULT_MEMORY ioctl (aka
> > KVM_MAP_MEMORY).
>
> To be more precise, params.len should be set to the number of bytes *left*, i.e.
>
> params.len -= ret * PAGE_SIZE;
> params.gfn_start += ret * PAGE_SIZE;
> if (params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO)
> params.uaddr += ret * PAGE_SIZE;
>
> Also this patch needs some other changes:
>
> 1) snp_launch_update() should have something like this:
>
> src = params.type == KVM_SEV_SNP_PAGE_TYPE_ZERO ? NULL :
> u64_to_user_ptr(params.uaddr),;
>
> so that then...
>
> > + vaddr = kmap_local_pfn(pfn + i);
> > + ret = copy_from_user(vaddr, src + i * PAGE_SIZE, PAGE_SIZE);
> > + if (ret) {
> > + pr_debug("Failed to copy source page into GFN 0x%llx\n", gfn);
> > + goto out_unmap;
> > + }
>
> ... the copy can be done only if src is non-NULL
>
> 2) the struct should have some more fields
>
> > + struct kvm_sev_snp_launch_update {
> > + __u64 gfn_start; /* Guest page number to load/encrypt data into. */
> > + __u64 uaddr; /* Userspace address of data to be loaded/encrypted. */
> > + __u32 len; /* 4k-aligned length in bytes to copy into guest memory.*/
> > + __u8 type; /* The type of the guest pages being initialized. */
>
> __u8 pad0;
> __u16 flags; // must be zero
> __u64 pad1[5];
>
> with accompanying flags check in snp_launch_update().
Have these all addressed in v14, but I ended up making 'len' a __u64, so the
final struct looks like this:
struct kvm_sev_snp_launch_update {
__u64 gfn_start;
__u64 uaddr;
__u64 len;
__u8 type;
__u8 pad0;
__u16 flags;
__u32 pad1;
__u64 pad2[4];
};
>
> If you think IMI can be implemented already (with a bit in flags) go
> ahead and do it.
Migration will also need related flags in LAUNCH_START, and depending on how
we implement things, possibly in LAUNCH_FINISH. So for now I've left IMI
out, but added similar 'flags' and padding to those structs as well so we have
some flexibility with how we end up handling that.
-Mike
>
> Paolo
>
