From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0421A3E3169 for ; Mon, 18 May 2026 09:10:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779095412; cv=none; b=S8Tai3ZrFfdanF7Lk+eoKBZRa9YOJdy9XEPN2DFLj1aTMTScRjgJeVxul10B6Q73fws0O2KN1SCSCJvTecxNuPTUgtXGAPV0kuH7m56oxJ1iUK+irDLkQ6PfIiQA33EWkerMIluDQ+O/Vaeoxgag/MJ9SLWx0jnYHzG6O3ZX8Gs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779095412; c=relaxed/simple; bh=yM606txQr59MpoGECD5z9Drm2fKlG81Jw2FQOPDpgSA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S8KdxT5rtd4eh2BnYOsaR5j7JbFReRkHi/K1jhIa2ywomtajzPIkiF8kPMDUszG44JXQ79Y0D+FJ0Eotv8XzMzQt/NwBjDe88pBSCIPjg4tVbV38iaPkfkb3mXiqhyoPu1Nl5euFGbTKYn8FFaVPm/JRsQcT6MpoUutCH4rFyXA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=seFe9iOY; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="seFe9iOY" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0A6E11CC4; Mon, 18 May 2026 02:10:04 -0700 (PDT) Received: from [10.57.21.187] (unknown [10.57.21.187]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0EA993F632; Mon, 18 May 2026 02:10:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1779095409; bh=yM606txQr59MpoGECD5z9Drm2fKlG81Jw2FQOPDpgSA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=seFe9iOYMIYwwiVKx1to9xsbDK/AbJWa6O0xL7bVnuRBEVde8M7ZKY1k/QCk1WurF mgXoL6ChaGT0Ai73++XxpriqutOChwTmZIGCveUVeXoYM8ZTzMFuuQxhWXj8twIyRP 54O0g52gMAEWxRyBcLzZgT9AM04V7Dg2vSli7Xn8= Message-ID: <721c3b69-52c4-44db-821e-55998beb5248@arm.com> Date: Mon, 18 May 2026 10:10:06 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] virt: arm-cca-guest: use raw variant of smp_processor_id() in arm_cca_report_new() Content-Language: en-GB To: Kohei Enju , Catalin Marinas , Will Deacon Cc: Sami Mujawar , Gavin Shan , Steven Price , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260518033157.1865498-1-enju.kohei@fujitsu.com> From: Suzuki K Poulose In-Reply-To: <20260518033157.1865498-1-enju.kohei@fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 18/05/2026 04:31, Kohei Enju wrote: > With CONFIG_DEBUG_PREEMPT=y, smp_processor_id() becomes an alias of > debug_smp_processor_id(). This debug function complains when certain > conditions that ensure CPU ID stability are not met, specifically when > it's called from a preemptible context. > > In arm_cca_report_new(), which runs in a preemptible context, > smp_processor_id() triggers a splat [0] due to this. > > However, the CPU ID obtained here is used as the target CPU for > smp_call_function_single() to designate a specific CPU for subsequent > operations, not to assert that the current thread will continue to > execute on the same CPU. Therefore, snapshotting the CPU ID itself is > correct, and thus there's no actual harm except for the splat. > > Use raw_smp_processor_id() instead, to directly retrieve the current CPU > ID without the debug checks, avoiding the unnecessary warning message > while preserving the correct functional behavior. > > [0] > BUG: using smp_processor_id() in preemptible [00000000] code: cca-workload-at/134 > caller is debug_smp_processor_id+0x20/0x2c > CPU: 0 UID: 0 PID: 134 Comm: cca-workload-at Not tainted 7.0.0-rc1-gc74a64d12073 #1 PREEMPT > Hardware name: linux,dummy-virt (DT) > Call trace: > [...] > check_preemption_disabled+0xf8/0x100 > debug_smp_processor_id+0x20/0x2c > arm_cca_report_new+0x54/0x230 > tsm_report_read+0x184/0x260 > tsm_report_outblob_read+0x18/0x38 > configfs_bin_read_iter+0xf4/0x1dc > vfs_read+0x230/0x31c > [...] > > Fixes: 7999edc484ca ("virt: arm-cca-guest: TSM_REPORT support for realms") > Signed-off-by: Kohei Enju Thank for the fix, Reviewed-by: Suzuki K Poulose > --- > drivers/virt/coco/arm-cca-guest/arm-cca-guest.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c b/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c > index 0c9ea24a200c..2d450caee3e4 100644 > --- a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c > +++ b/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c > @@ -108,7 +108,7 @@ static int arm_cca_report_new(struct tsm_report *report, void *data) > * allocate outblob based on the returned value from the 'init' > * call and that cannot be done in an atomic context. > */ > - cpu = smp_processor_id(); > + cpu = raw_smp_processor_id(); > > info.challenge = desc->inblob; > info.challenge_size = desc->inblob_len;