From: Julien Grall <julien@xen.org>
To: Jan Beulich <jbeulich@suse.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH] x86/AMD: adjust SYSCFG, TOM, etc exposure to deal with running nested
Date: Mon, 19 Jul 2021 10:18:48 +0100 [thread overview]
Message-ID: <d8913811-2e90-255b-98c6-44e262e113d3@xen.org> (raw)
In-Reply-To: <cd23fd18-66f9-55c7-4a1c-a50d66628d69@suse.com>
Hi Jan,
On 13/07/2021 08:22, Jan Beulich wrote:
> In the original change I neglected to consider the case of us running as
> L1 under another Xen. In this case we're not Dom0, so the underlying Xen
> wouldn't permit us access to these MSRs. As an immediate workaround use
> rdmsr_safe(); I don't view this as the final solution though, as the
> original problem the earlier change tried to address also applies when
> running nested. Yet it is then unclear to me how to properly address the
> issue: We shouldn't generally expose the MSR values, but handing back
> zero (or effectively any other static value) doesn't look appropriate
> either.
IIUC, the unsolved problem is a Linux 3.12 dom0 running on top of the L1
Xen. The kernel is quite old (and looks to be unsupported), so are we
expecting anyone to build a new stack with a newer Xen and such dom0?
If the answer is unlikely, then I think it would be fair to keep the
limitation until someone comes up with such setup.
>
> Fixes: bfcdaae9c210 ("x86/AMD: expose SYSCFG, TOM, TOM2, and IORRs to Dom0")
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Cheers,
--
Julien Grall
next prev parent reply other threads:[~2021-07-19 9:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-13 7:22 [PATCH] x86/AMD: adjust SYSCFG, TOM, etc exposure to deal with running nested Jan Beulich
2021-07-19 9:18 ` Julien Grall [this message]
2021-07-19 9:30 ` Jan Beulich
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