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Message-ID: <87eddomoov.ffs@tglx>
Date: Wed, 07 Feb 2024 13:41:36 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Marcelo Tosatti <mtosatti@...hat.com>, linux-kernel@...r.kernel.org
Cc: Daniel Bristot de Oliveira <bristot@...nel.org>, Juri Lelli
<juri.lelli@...hat.com>, Valentin Schneider <vschneid@...hat.com>,
Frederic Weisbecker <frederic@...nel.org>, Leonardo Bras
<leobras@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Marcelo
Tosatti <mtosatti@...hat.com>
Subject: Re: [patch 12/12] x86/cacheinfo.c: check for block interference CPUs
On Tue, Feb 06 2024 at 15:49, Marcelo Tosatti wrote:
> @@ -396,6 +397,7 @@ static void amd_l3_disable_index(struct
> * disable index in all 4 subcaches
> */
> for (i = 0; i < 4; i++) {
> + int ret;
> u32 reg = idx | (i << 20);
>
> if (!nb->l3_cache.subcaches[i])
> @@ -409,6 +411,7 @@ static void amd_l3_disable_index(struct
> * is not sufficient.
> */
> ret = wbinvd_on_cpu(cpu);
> + WARN_ON(ret == -EPERM);
What? You create inconsistent state here.
> - amd_l3_disable_index(nb, cpu, slot, index);
> + ret = 0;
> + idx = block_interf_srcu_read_lock();
> +
> + if (block_interf_cpu(cpu))
> + ret = -EPERM;
> + else
> + amd_l3_disable_index(nb, cpu, slot, index);
> +
> + block_interf_srcu_read_unlock(idx);
Again. This is a root only operation.
This whole patch series is just voodoo programming with zero
justification for the mess it creates.
Thanks,
tglx
.
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