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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: riel@surriel.com On Thu, 2024-11-14 at 10:52 +0100, Ingo Molnar wrote: >=20 > * Rik van Riel wrote: >=20 > > On Wed, 13 Nov 2024 10:55:50 +0100 > > Borislav Petkov wrote: > >=20 > > > On Fri, Nov 08, 2024 at 07:27:47PM -0500, Rik van Riel wrote: > > > > While profiling switch_mm_irqs_off with several workloads, > > > > it appears there are two hot spots that probably don't need > > > > to be there.=C2=A0=20 > > >=20 > > > One of those three is causing the below here, zapping them from > > > tip. > > >=20 > >=20 > > TL;DR: __text_poke ends up sending IPIs with interrupts disabled. > >=20 > > > [=C2=A0=C2=A0=C2=A0 3.186469]=C2=A0 on_each_cpu_cond_mask+0x50/0x90 > > > [=C2=A0=C2=A0=C2=A0 3.186469]=C2=A0 flush_tlb_mm_range+0x1a8/0x1f0 > > > [=C2=A0=C2=A0=C2=A0 3.186469]=C2=A0 ? cpu_bugs_smt_update+0x14/0x1f0 > > > [=C2=A0=C2=A0=C2=A0 3.186469]=C2=A0 __text_poke+0x366/0x5d0 > >=20 > > Here is an alternative to avoid __text_poke() from calling > > on_each_cpu_cond_mask() with IRQs disabled: > >=20 > > ---8<--- > > From e872edeaad14c793036f290afc28000281e1b76a Mon Sep 17 00:00:00 > > 2001 > > From: Rik van Riel > > Date: Wed, 13 Nov 2024 09:51:16 -0500 > > Subject: [PATCH] x86/alternatives: defer poking_mm TLB flush to > > next use >=20 > I'd argue *both* of your patches improve the code, right? >=20 We have 3 possible solutions, and I think we only need one of them. > Mind sending an updated series? It might not make it into the merge > window, > but these look like good changes to me. I would be happy to send a new series, but it would be good if we agreed on what solution we wanted :) 1) Move the interrupt re-enabling up (probably not this one?) 2) Explicitly clear the mm_cpumask bit in unuse_temporary_mm() 3) Have unuse_temporary_mm increment the mm's tlb_gen, since that is the only thing flush_tlb_mm_range really does for an MM without any bits set in the mm_cpumask. Which one would you guys prefer? --=20 All Rights Reversed.