From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D5E60CAC5B8 for ; Mon, 6 Oct 2025 10:08:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:Message-ID:In-Reply-To:Date:From:Cc:To:Subject: Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender :Resent-To:Resent-Cc:Resent-Message-ID:References:List-Owner; bh=k72vCdxIP2nzAHjs9T2IdzHUDYmI71aTc4xVjgJiHJA=; b=PlyrcpjF+BTm92TtFipW6mSi93 oC7kOFAhH7G4VP/Rm8WjpTqtkpABuLmXpI2dh7/QMqJDdZMEPxU5FAUKGwocMeRwdewr3ptZVxEtL 11zdI7gyJWbAvXKxim5WnoF3nBwGsxp6NrFp/3ycVV8E1d05/1yM/raAS33tiE9zer2BslgSquCdj 5zRaPUUm+L3HDnWEekPGsESu20+IKv8gPmvU9qnQtjw1gMe5XvIBQSo+TLWmwFoPewpJ9uZy7ZMMv oaa5j2H/nYXki5Bd3r4IHdHexujn3Ri0g1hNDZFlzX0GSmSL2nnKWkYc5iwzS1YSoVZeRVtoM1rzz sIUk7soA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v5i8c-0000000HKHn-1GPS; Mon, 06 Oct 2025 10:08:14 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v5i8a-0000000HKGd-1ltf for linux-arm-kernel@lists.infradead.org; Mon, 06 Oct 2025 10:08:13 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id F3823409DB; Mon, 6 Oct 2025 10:08:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BB0CC4CEFF; Mon, 6 Oct 2025 10:08:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759745290; bh=r5zitekIrWErqgknk1Y+49yJJgQ8ROvH0QJOlT15OnE=; h=Subject:To:Cc:From:Date:In-Reply-To:From; b=JpWNc7nin+LmgMHyNk8gBcQg2sF7FPTBape92VeavX2zNw60dnA2xKDoNDTyoDngK MFxzBhyTmDfyav7h4Xg6wkG2HNbJ1skfwOSVL05N1QAmttVbcc/SQ5YyOdm7Wm4nLS UN57RxvliNqtaDhcGJr1AzSekpoKFv8mx1ctt50k= Subject: Patch "KVM: arm64: Fix softirq masking in FPSIMD register saving sequence" has been added to the 5.15-stable tree To: ardb@kernel.org,gregkh@linuxfoundation.org,kvanals@kvanals.org,kvmarm@lists.linux.dev,lee@kernel.org,linux-arm-kernel@lists.infradead.org,sashal@kernel.org,will@kernel.org Cc: From: Date: Mon, 06 Oct 2025 12:08:08 +0200 In-Reply-To: <20251003183917.4209-1-will@kernel.org> Message-ID: <2025100608-vision-handmade-551d@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit X-stable: commit X-Patchwork-Hint: ignore X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251006_030812_610140_A24794AB X-CRM114-Status: GOOD ( 14.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org This is a note to let you know that I've just added the patch titled KVM: arm64: Fix softirq masking in FPSIMD register saving sequence to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-arm64-fix-softirq-masking-in-fpsimd-register-saving-sequence.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >From will@kernel.org Mon Oct 6 11:59:13 2025 From: Will Deacon Date: Fri, 3 Oct 2025 19:39:17 +0100 Subject: KVM: arm64: Fix softirq masking in FPSIMD register saving sequence To: stable@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, Will Deacon , Ard Biesheuvel , Lee Jones , Sasha Levin , Kenneth Van Alstyne Message-ID: <20251003183917.4209-1-will@kernel.org> From: Will Deacon Stable commit 23249dade24e ("KVM: arm64: Fix kernel BUG() due to bad backport of FPSIMD/SVE/SME fix") fixed a kernel BUG() caused by a bad backport of upstream commit fbc7e61195e2 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") by ensuring that softirqs are disabled/enabled across the fpsimd register save operation. Unfortunately, although this fixes the original issue, it can now lead to deadlock when re-enabling softirqs causes pending softirqs to be handled with locks already held: | BUG: spinlock recursion on CPU#7, CPU 3/KVM/57616 | lock: 0xffff3045ef850240, .magic: dead4ead, .owner: CPU 3/KVM/57616, .owner_cpu: 7 | CPU: 7 PID: 57616 Comm: CPU 3/KVM Tainted: G O 6.1.152 #1 | Hardware name: SoftIron SoftIron Platform Mainboard/SoftIron Platform Mainboard, BIOS 1.31 May 11 2023 | Call trace: | dump_backtrace+0xe4/0x110 | show_stack+0x20/0x30 | dump_stack_lvl+0x6c/0x88 | dump_stack+0x18/0x34 | spin_dump+0x98/0xac | do_raw_spin_lock+0x70/0x128 | _raw_spin_lock+0x18/0x28 | raw_spin_rq_lock_nested+0x18/0x28 | update_blocked_averages+0x70/0x550 | run_rebalance_domains+0x50/0x70 | handle_softirqs+0x198/0x328 | __do_softirq+0x1c/0x28 | ____do_softirq+0x18/0x28 | call_on_irq_stack+0x30/0x48 | do_softirq_own_stack+0x24/0x30 | do_softirq+0x74/0x90 | __local_bh_enable_ip+0x64/0x80 | fpsimd_save_and_flush_cpu_state+0x5c/0x68 | kvm_arch_vcpu_put_fp+0x4c/0x88 | kvm_arch_vcpu_put+0x28/0x88 | kvm_sched_out+0x38/0x58 | __schedule+0x55c/0x6c8 | schedule+0x60/0xa8 Take a tiny step towards the upstream fix in 9b19700e623f ("arm64: fpsimd: Drop unneeded 'busy' flag") by additionally disabling hardirqs while saving the fpsimd registers. Cc: Ard Biesheuvel Cc: Lee Jones Cc: Sasha Levin Cc: # 5.15.y Fixes: 23249dade24e ("KVM: arm64: Fix kernel BUG() due to bad backport of FPSIMD/SVE/SME fix") Reported-by: Kenneth Van Alstyne Link: https://lore.kernel.org/r/010001999bae0958-4d80d25d-8dda-4006-a6b9-798f3e774f6c-000000@email.amazonses.com Signed-off-by: Will Deacon Acked-by: Ard Biesheuvel Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/fpsimd.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1300,13 +1300,17 @@ static void fpsimd_flush_cpu_state(void) */ void fpsimd_save_and_flush_cpu_state(void) { + unsigned long flags; + if (!system_supports_fpsimd()) return; WARN_ON(preemptible()); - get_cpu_fpsimd_context(); + local_irq_save(flags); + __get_cpu_fpsimd_context(); fpsimd_save(); fpsimd_flush_cpu_state(); - put_cpu_fpsimd_context(); + __put_cpu_fpsimd_context(); + local_irq_restore(flags); } #ifdef CONFIG_KERNEL_MODE_NEON Patches currently in stable-queue which might be from will@kernel.org are queue-5.15/kvm-arm64-fix-softirq-masking-in-fpsimd-register-saving-sequence.patch