From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7073831280A; Fri, 22 Aug 2025 14:25:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755872732; cv=none; b=PKyc1E2kqCaPiEgu0KsfGWHesC9VavRRR15nzpK0fa0xZgkhxTTLTTSs/s1E+MmtvSh14BuvbleG4Q3K7JY4jDTBhkljLGhaa2S2+8b3/AEkF8jmyY0xrMfCNUQlhOToIXlWynT7XOyc+GNJ2tAJubf3fru1ySeg1JJcXecLX0o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755872732; c=relaxed/simple; bh=Ce8xVjTX+LdoK8WYSQNLB8XNPREgItbTHqmQpvQAYkc=; h=Subject:To:Cc:From:Date:In-Reply-To:Message-ID:MIME-Version: Content-Type; b=hrkANnJtqZhkZaVVUseTiPVRoPQqxT9tyXtSpOrYLhmaMlMLO74ogYsz9BX+1g5vMjlvZPkSVMrPscypYexkloyFTuD7q4RIQSuInjquhX4F/KV6sD1EV7c2Xh18S3Nxj2qEWy7HDrE2/C9n+mNnr2tTMwqMABlK4Yk9a68rV0I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BSe20ul5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BSe20ul5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84E9AC4CEED; Fri, 22 Aug 2025 14:25:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755872732; bh=Ce8xVjTX+LdoK8WYSQNLB8XNPREgItbTHqmQpvQAYkc=; h=Subject:To:Cc:From:Date:In-Reply-To:From; b=BSe20ul57KuSwSNT0pYtd50nT03RRVTm0wI9xPlrL0e2DvOsIRcnTYhSeAKbzxeHw 3eU4mf4zV9JDqJeaVQCPbB/q5ILYygixpzH5CPfym+30F5B3z+iiGSN1z6rGhbfvtp OKpNWQfhyskt/XnQDvKU7R3eoSHMcdM+efXn1+HI= Subject: Patch "KVM: arm64: Fix kernel BUG() due to bad backport of FPSIMD/SVE/SME fix" has been added to the 5.15-stable tree To: ardb@kernel.org,gregkh@linuxfoundation.org,kvmarm@lists.linux.dev,lee@kernel.org,linux-arm-kernel@lists.infradead.org,mark.rutland@arm.com,maz@kernel.org,sashal@kernel.org,tabba@google.com,will@kernel.org Cc: From: Date: Fri, 22 Aug 2025 16:25:28 +0200 In-Reply-To: <20250822140402.2688-1-will@kernel.org> Message-ID: <2025082228-camper-turtle-e085@gregkh> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit X-stable: commit X-Patchwork-Hint: ignore This is a note to let you know that I've just added the patch titled KVM: arm64: Fix kernel BUG() due to bad backport of FPSIMD/SVE/SME fix 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-kernel-bug-due-to-bad-backport-of-fpsimd-sve-sme-fix.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 Fri Aug 22 16:24:21 2025 From: Will Deacon Date: Fri, 22 Aug 2025 15:04:02 +0100 Subject: KVM: arm64: Fix kernel BUG() due to bad backport of FPSIMD/SVE/SME fix To: stable@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, Will Deacon , Ard Biesheuvel , Lee Jones , Sasha Levin , Greg Kroah-Hartman , Mark Rutland , Fuad Tabba , Marc Zyngier Message-ID: <20250822140402.2688-1-will@kernel.org> From: Will Deacon Upstream commit fbc7e61195e2 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") relies on interrupts being disabled during fpsimd_save_and_flush_cpu_state() so that a softirq cannot be taken while the host floating point context is being saved and potentially try to use kernel-mode NEON. Unfortunately, stable kernels without 9b19700e623f ("arm64: fpsimd: Drop unneeded 'busy' flag") leave interrupts enabled in fpsimd_save_and_flush_cpu_state() and so the BUG_ON(!may_use_simd()) in kernel_neon_begin() has been observed to trigger in real-world usage: | kernel BUG at arch/arm64/kernel/fpsimd.c:1904! | Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP | | Call trace: | kernel_neon_begin+0xdc/0x12c | ... | crypto_aead_decrypt+0x5c/0x6c | seqiv_aead_decrypt+0x88/0x9c | crypto_aead_decrypt+0x5c/0x6c | esp_input+0x280/0x364 | xfrm_input+0x6ac/0x16f8 | ... | net_rx_action+0x13c/0x31c | handle_softirqs+0x124/0x3d0 | __do_softirq+0x14/0x20 | ____do_softirq+0x10/0x20 | call_on_irq_stack+0x3c/0x74 | do_softirq_own_stack+0x1c/0x2c | __irq_exit_rcu+0x54/0xb4 | irq_exit_rcu+0x10/0x1c | el1_interrupt+0x38/0x58 | el1h_64_irq_handler+0x18/0x24 | el1h_64_irq+0x68/0x6c | fpsimd_save+0xe4/0x130 | kvm_arch_vcpu_load_fp+0x2c/0x58 | kvm_arch_vcpu_load+0x88/0x26c | kvm_sched_in+0x2c/0x3c Given that 9b19700e623f ("arm64: fpsimd: Drop unneeded 'busy' flag") is not a fix in its own right, has non-trivial dependencies and is a reasonably invasive change to the in-kernel use of fpsimd, opt instead for a simple fix to use the softirq-safe {get,put}_cpu_fpsimd_context() helpers in fpsimd_save_and_flush_cpu_state(). Cc: Ard Biesheuvel Cc: Lee Jones Cc: Sasha Levin Cc: Mark Rutland Cc: Fuad Tabba Cc: Marc Zyngier Cc: # 5.15.y, 6.1.y and 6.6.y Fixes: 806d5c1e1d2e ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") # 6.6.y Fixes: 04c50cc23a49 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") # 6.1.y Fixes: 5289ac43b69c ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") # 5.15.y Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/fpsimd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1303,10 +1303,10 @@ void fpsimd_save_and_flush_cpu_state(voi if (!system_supports_fpsimd()) return; WARN_ON(preemptible()); - __get_cpu_fpsimd_context(); + get_cpu_fpsimd_context(); fpsimd_save(); fpsimd_flush_cpu_state(); - __put_cpu_fpsimd_context(); + put_cpu_fpsimd_context(); } #ifdef CONFIG_KERNEL_MODE_NEON Patches currently in stable-queue which might be from will@kernel.org are queue-5.15/kvm-arm64-fix-kernel-bug-due-to-bad-backport-of-fpsimd-sve-sme-fix.patch queue-5.15/arm64-mark-kernel-as-tainted-on-sae-and-serror-panic.patch queue-5.15/arm64-entry-mask-daif-in-cpu_switch_to-call_on_irq_stack.patch queue-5.15/mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd.patch