From: Borislav Petkov <bp@alien8.de>
To: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: linux-kernel@vger.kernel.org, Mark Gross <mgross@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
John Johansen <john.johansen@canonical.com>,
Steve Beattie <sbeattie@ubuntu.com>
Subject: Re: [PATCH] x86/speculation/srbds: do not try to turn mitigation off when not supported
Date: Mon, 15 Jun 2020 10:28:58 +0200 [thread overview]
Message-ID: <20200615082858.GC14668@zn.tnic> (raw)
In-Reply-To: <20200609174313.2600320-1-cascardo@canonical.com>
On Tue, Jun 09, 2020 at 02:43:13PM -0300, Thadeu Lima de Souza Cascardo wrote:
> When SRBDS is mitigated by TSX OFF, update_srbds_msr will still read and
Are you talking about this case in srbds_select_mitigation():
if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM))
srbds_mitigation = SRBDS_MITIGATION_TSX_OFF;
?
and you have a system which:
* Check to see if this is one of the MDS_NO systems supporting
* TSX that are only exposed to SRBDS when TSX is enabled.
i.e., no SRBDS microcode for it and the fix is to disable TSX?
If so, I think the right fix should be to do:
if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
return;
in update_srbds_msr() with a comment above it explaining why that check
is being done.
Hmmm.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-06-15 8:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-09 17:43 Thadeu Lima de Souza Cascardo
2020-06-15 8:28 ` Borislav Petkov [this message]
2020-06-15 10:27 ` Thadeu Lima de Souza Cascardo
2020-06-15 10:47 ` Borislav Petkov
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