From: Andrew Cooper <andrew.cooper3@citrix.com>
To: "Jan Beulich" <jbeulich@suse.com>,
"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
zachm1996@gmail.com, Claudia <claudia1@disroot.org>
Subject: Re: [Xen-devel] Xen fails to resume on AMD Fam15h (and Fam17h?) because of CPUID mismatch
Date: Mon, 10 Feb 2020 11:17:34 +0000 [thread overview]
Message-ID: <41b3896b-5414-bfdf-a515-bf2f06ab6463@citrix.com> (raw)
In-Reply-To: <a6b9455d-dea1-6c61-ff7f-4fbaaba9a953@suse.com>
On 10/02/2020 08:55, Jan Beulich wrote:
> On 10.02.2020 00:06, Marek Marczykowski-Górecki wrote:
>> Hi,
>>
>> Multiple Qubes users have reported issues with resuming from S3 on AMD
>> systems (Ryzen 2500U, Ryzen Pro 3700U, maybe more). The error message
>> is:
>>
>> (XEN) CPU0: cap[ 1] is 7ed8320b (expected f6d8320b)
>>
>> If I read it right, this is:
>> - OSXSAVE: 0 -> 1
>> - HYPERVISOR: 1 -> 0
>>
>> Commenting out the panic on a failed recheck_cpu_features() in power.c
>> makes the system work after resume, reportedly stable. But that doesn't
>> sounds like a good idea generally.
>>
>> Is this difference a Xen fault (some missing MSR / other register
>> restore on resume)? Or BIOS vendor / AMD, that could be worked around in
>> Xen?
> The transition of the HYPERVISOR bit is definitely a Xen issue,
> with Andrew having sent a patch already (iirc).
https://lore.kernel.org/xen-devel/20200127202121.2961-1-andrew.cooper3@citrix.com/
Code is correct. Commit message needs rework, including in light of
this discovery. (I may eventually split it into two patches.)
> The OSXSAVE part is a little more surprising,
Not to me. The checks only care if feature bits have gone missing, not
if new ones have appeared.
mmu_cr4_features includes OSXSAVE (from much later on boot than features
get cached), so the s3 path observing the gain of OSXSAVE will have been
happening ever since the checks were introduced (even on Intel.)
~Andrew
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next prev parent reply other threads:[~2020-02-10 11:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-09 23:06 [Xen-devel] Xen fails to resume on AMD Fam15h (and Fam17h?) because of CPUID mismatch Marek Marczykowski-Górecki
2020-02-10 8:55 ` Jan Beulich
2020-02-10 11:17 ` Andrew Cooper [this message]
2020-02-10 12:14 ` Marek Marczykowski-Górecki
2020-02-10 12:46 ` Andrew Cooper
2020-02-11 12:59 ` Claudia
2020-02-11 21:08 ` Marek Marczykowski-Górecki
2020-02-12 4:20 ` Claudia
2020-05-02 21:12 ` Z M
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