From: Rik van Riel <riel@surriel.com>
To: Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com
Subject: Re: [PATCH] add tlbi=off to disable INVLPGB
Date: Fri, 31 Jul 2026 07:47:36 -0400 [thread overview]
Message-ID: <ab81ee1baaee8e3884e982156003984cc3cfd1f3.camel@surriel.com> (raw)
In-Reply-To: <20260731084656.GF776954@noisy.programming.kicks-ass.net>
On Fri, 2026-07-31 at 10:46 +0200, Peter Zijlstra wrote:
> On Thu, Jul 30, 2026 at 11:24:39AM -0700, Borislav Petkov wrote:
>
> >
> > We probably won't need to write "bcast" at all, actually, because
> > that would
> > be the default. So "tlbi=ipi" only. Yeah, that's good.
>
> Didn't we have a case where INVLPGB was disabled due to firmware or
> something? I was thinking tlbi=broadcast could be used to force
> enable
> it or something.
I have a mini PC here that does just that.
lspcu says:
AMD Ryzen 9 7940HS w/ Radeon 780M Graphics
That suggests the core should have INVLPGB built-in,
but it shows up as disabled in cpuid.
$ cpuid -1 | grep INVLPGB
INVLPGB instruction = false
INVLPGB supports TLB flush guest nested = false
max page count for INVLPGB instruction = 0x0 (0)
INVLPGB/TLBSYNC hyperv interc enable = false
I have not been able to find a BIOS option that
results in it being enabled.
--
All Rights Reversed.
next prev parent reply other threads:[~2026-07-31 11:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-30 0:43 Rik van Riel
2026-07-30 1:44 ` Borislav Petkov
2026-07-30 10:32 ` Peter Zijlstra
2026-07-30 16:23 ` Borislav Petkov
2026-07-30 17:31 ` Peter Zijlstra
2026-07-30 18:24 ` Borislav Petkov
2026-07-31 8:46 ` Peter Zijlstra
2026-07-31 9:14 ` David Laight
2026-07-31 11:47 ` Rik van Riel [this message]
2026-07-31 18:32 ` Borislav Petkov
2026-08-06 15:54 ` [PATCH] x86/CPU: Add a tlbi= cmdline switch Borislav Petkov
2026-08-10 16:47 ` [tip: x86/urgent] " tip-bot2 for Rik van Riel
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