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Date:   Wed, 12 May 2021 11:32:35 +0200
From:   Joerg Roedel <jroedel@suse.de>
To:     Juergen Gross <jgross@suse.com>
Cc:     'Joerg Roedel' <joro@8bytes.org>,
        David Laight <David.Laight@aculab.com>,
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        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Jiri Slaby <jslaby@suse.cz>,
        Dan Williams <dan.j.williams@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
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        Masami Hiramatsu <mhiramat@kernel.org>,
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Subject: Re: [PATCH 3/6] x86/sev-es: Use __put_user()/__get_user
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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