On Wed, May 12, 2021 at 10:58:20AM +0200, Juergen Gross wrote:

No, those were used before, but commit 9da3f2b7405440 broke Xen's use
case. That is why I did commit 1457d8cf7664f.

I see, thanks for the heads-up. So here this is not a big issue, because
when an access to kernel space faults under SEV-ES, its a kernel bug
anyway. The issue is that it is not reported correctly.

I think I need to re-work the helper and use probe_kernel_read/write()
when the address is in kernel space. This distinction is already made
when fetching instruction bytes in the #VC handler, but I thought I
could get around it for data accesses.

Having the distinction between user and kernel memory accesses
explicitly in the code seems to be the most robust solution.

Regards,

	Joerg