From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>,
Jane Malalane <jane.malalane@citrix.com>
Cc: "Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
"Pu Wen" <puwen@hygon.cn>, "Andy Lutomirski" <luto@kernel.org>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v2 2/2] x86/cpuid: Detect null segment behaviour on Zen2 CPUs
Date: Wed, 8 Sep 2021 13:28:35 +0100 [thread overview]
Message-ID: <e89a7269-351c-6bdc-60e7-5b58399f1e31@citrix.com> (raw)
In-Reply-To: <a27d3631-86a3-cacc-efd6-97b02e3f8b94@suse.com>
On 08/09/2021 13:08, Jan Beulich wrote:
> On 08.09.2021 10:19, Jane Malalane wrote:
>> Zen2 CPUs actually have this behaviour, but the CPUID bit couldn't be
>> introduced into Zen2 due to a lack of leaves. So, it was added in a
>> new leaf in Zen3. Nonetheless, hypervisors can synthesize the CPUID
>> bit in software.
> Considering the prior model checks, I understand this isn't all Zen2s?
> No matter what the answer, I'd like to ask that the first sentence
> start with either "All" or "Some" (or something along these lines).
> Which is of course fine to insert while committing, so not need to
> send a v3.
All Zen2's have this behaviour.
The model checks were trying to avoid running the probe on Zen1, but
"model >= 0x30 && mode != 0x50" is error prone.
There are no faults in the probe, and its fast, so running on all Zen1/2
is better than hoping that we got the model list correct.
~Andrew
prev parent reply other threads:[~2021-09-08 12:28 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-06 12:00 [PATCH v1 0/2] x86/cpuid: Use AMD's NullSelectorClearsBase CPUID bit Jane Malalane
2021-09-06 12:00 ` [PATCH v1 1/2] x86/cpuid: Expose NullSelectorClearsBase CPUID bit to guests Jane Malalane
2021-09-06 15:04 ` Jan Beulich
2021-09-06 19:20 ` Andrew Cooper
2021-09-06 12:00 ` [PATCH v1 2/2] x86/cpuid: Detect null segment behaviour on Zen2 CPUs Jane Malalane
2021-09-06 15:17 ` Jan Beulich
2021-09-06 18:07 ` Andrew Cooper
2021-09-07 6:09 ` Jan Beulich
2021-09-07 13:27 ` Andrew Cooper
2021-09-07 14:21 ` Jan Beulich
2021-09-08 8:19 ` [PATCH v2 " Jane Malalane
2021-09-08 12:08 ` Jan Beulich
2021-09-08 12:28 ` Andrew Cooper [this message]
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