From nobody Mon Feb 9 12:24:32 2026 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 24D891EFF87; Fri, 4 Apr 2025 13:27:44 +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=1743773265; cv=none; b=QUyQhebElQHO0RosVmKFO572ZszpfkMW/NUOhUb6i+KJ9TNCCB7Oei3hBRM+OIUZLjEa9v8NFBKpodePFT65ArbtGT3U4yBw+dVyzfnEkNkHzZWNqX4pIrvkqQllfSvcCAVnZygFTJUtoH5gA7nLd2/ZRZisYNMr7FWigvBhLF0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743773265; c=relaxed/simple; bh=RRrgm1q6EeT2E848Is7OgtYEI0k9m9Vbvkpw1yYV0SY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=OjtcKKma/5AkOdCnc1Xzbd55H806UxIW5BV9rtcfQCJ6iggaIn503kjHVsiUflEhbVEeeSDY8Y3fuZtTlXyzLNXI03EhUO+QrZlCfIKNx84HPPJEZZNAW8GTcnrNvfw4fjMh+66KnoqcJvw49zDnJkE8qzAGXp+ahmQe4YXNnE4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Fx+CMP94; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Fx+CMP94" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 87691C4CEE8; Fri, 4 Apr 2025 13:27:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743773264; bh=RRrgm1q6EeT2E848Is7OgtYEI0k9m9Vbvkpw1yYV0SY=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Fx+CMP94+MV0H0NH20YNkySVoT3FQSOTYf1hsHo3QznxfnlEip4MG368OOpUzzZvM 7kZ6FT41NPo9e9bqtnM2Ix3/narlWi4cfEoI8QbcC7Ld/RWk78QAvSBH+oJt6fZA+c HLMibXgVT2/B1/mIlustB/43rt7A7JIBIn59B5f9nY7LFICiBlI11fM2cm9N4j5zCx aYmaNivKEG4BOBEMB/y/eaYVOemN57Du45I0KPmlaq5GrHnXzNJ2MCHWv68A1o6EDN fKRg9DE/HTrjIURUHwPo4QqcnjKxSM//y2quYnuFmfihlJRZehYu9WaX3bVaE+a9iy qQZdOkDtZk1tw== From: Mark Brown Date: Fri, 04 Apr 2025 14:23:38 +0100 Subject: [PATCH RESEND 6.1 05/12] KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250404-stable-sve-6-1-v1-5-cd5c9eb52d49@kernel.org> References: <20250404-stable-sve-6-1-v1-0-cd5c9eb52d49@kernel.org> In-Reply-To: <20250404-stable-sve-6-1-v1-0-cd5c9eb52d49@kernel.org> To: Catalin Marinas , Will Deacon , Marc Zyngier , James Morse , Suzuki K Poulose , Oliver Upton , Oleg Nesterov , Greg Kroah-Hartman Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, Mark Brown , stable@vger.kernel.org, Mark Rutland , Eric Auger , Wilco Dijkstra , Eric Auger , Florian Weimer , Fuad Tabba , Jeremy Linton , Paolo Bonzini X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=5370; i=broonie@kernel.org; h=from:subject:message-id; bh=1aPGpSPcZz/+QejW/+rfK2C2Ou9/JMy1RmOqGT2RPKc=; b=owEBbAGT/pANAwAKASTWi3JdVIfQAcsmYgBn794x/as9Dtp3/K1sGWHY+A01G1WEmhQtqdMt2ubW 11U0UKuJATIEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ+/eMQAKCRAk1otyXVSH0FbnB/ dYMFeUdMWGyNJP/zBhNKpYDQAAzSidAnZX0UXHuZf2JbeN6N/S23JgBBLzUDXTOsf9ETtVMZiy7wQQ 3cr3Zbd1OCLlydGDHrwxPymN7LEGBLGkTbj5dHH7SQyELWUzxTLpmB19qnJoHAFFWLQ/Z18Tpdx3bl KTzRM6wEouGHIBvRQmqCVJ1NEtJrKNqMi8ev3AAsSHGXGp5skHfH5xFTLl+6JBzfcOcmuV7Mm4/U5I lVJj9V0oetL+Kp6jsxgAqwR2ALLwusIv6RFw/rGEiny5rM6XTvlp6Eo5DGgO0jQjarkfu7A/r/XoPI TkNwofqgloeIk/4ET2TvXnwslHdh8= X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB From: Mark Rutland [ Upstream commit fbc7e61195e23f744814e78524b73b59faa54ab4 ] There are several problems with the way hyp code lazily saves the host's FPSIMD/SVE state, including: * Host SVE being discarded unexpectedly due to inconsistent configuration of TIF_SVE and CPACR_ELx.ZEN. This has been seen to result in QEMU crashes where SVE is used by memmove(), as reported by Eric Auger: https://issues.redhat.com/browse/RHEL-68997 * Host SVE state is discarded *after* modification by ptrace, which was an unintentional ptrace ABI change introduced with lazy discarding of SVE st= ate. * The host FPMR value can be discarded when running a non-protected VM, where FPMR support is not exposed to a VM, and that VM uses FPSIMD/SVE. In these cases the hyp code does not save the host's FPMR before unbinding the host's FPSIMD/SVE/SME state, leaving a stale value in memory. Avoid these by eagerly saving and "flushing" the host's FPSIMD/SVE/SME state when loading a vCPU such that KVM does not need to save any of the host's FPSIMD/SVE/SME state. For clarity, fpsimd_kvm_prepare() is removed and the necessary call to fpsimd_save_and_flush_cpu_state() is placed in kvm_arch_vcpu_load_fp(). As 'fpsimd_state' and 'fpmr_ptr' should not be used, they are set to NULL; all uses of these will be removed in subsequent patches. Historical problems go back at least as far as v5.17, e.g. erroneous assumptions about TIF_SVE being clear in commit: 8383741ab2e773a9 ("KVM: arm64: Get rid of host SVE tracking/saving") ... and so this eager save+flush probably needs to be backported to ALL stable trees. Fixes: 93ae6b01bafee8fa ("KVM: arm64: Discard any SVE state when entering K= VM guests") Fixes: 8c845e2731041f0f ("arm64/sve: Leave SVE enabled on syscall if we don= 't context switch") Fixes: ef3be86021c3bdf3 ("KVM: arm64: Add save/restore support for FPMR") Reported-by: Eric Auger Reported-by: Wilco Dijkstra Reviewed-by: Mark Brown Tested-by: Mark Brown Tested-by: Eric Auger Acked-by: Will Deacon Cc: Catalin Marinas Cc: Florian Weimer Cc: Fuad Tabba Cc: Jeremy Linton Cc: Marc Zyngier Cc: Oliver Upton Cc: Paolo Bonzini Signed-off-by: Mark Rutland Reviewed-by: Oliver Upton Link: https://lore.kernel.org/r/20250210195226.1215254-2-mark.rutland@arm.c= om Signed-off-by: Marc Zyngier [ Mark: Handle vcpu/host flag conflict, remove host_data_ptr() ] Signed-off-by: Mark Rutland Signed-off-by: Mark Brown --- arch/arm64/kernel/fpsimd.c | 25 ------------------------- arch/arm64/kvm/fpsimd.c | 18 ++++++++++-------- 2 files changed, 10 insertions(+), 33 deletions(-) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 3fcacbce5d42..47425311acc5 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1671,31 +1671,6 @@ void fpsimd_signal_preserve_current_state(void) sve_to_fpsimd(current); } =20 -/* - * Called by KVM when entering the guest. - */ -void fpsimd_kvm_prepare(void) -{ - if (!system_supports_sve()) - return; - - /* - * KVM does not save host SVE state since we can only enter - * the guest from a syscall so the ABI means that only the - * non-saved SVE state needs to be saved. If we have left - * SVE enabled for performance reasons then update the task - * state to be FPSIMD only. - */ - get_cpu_fpsimd_context(); - - if (test_and_clear_thread_flag(TIF_SVE)) { - sve_to_fpsimd(current); - current->thread.fp_type =3D FP_STATE_FPSIMD; - } - - put_cpu_fpsimd_context(); -} - /* * Associate current's FPSIMD context with this cpu * The caller must have ownership of the cpu FPSIMD context before calling diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index ec82d0191f76..1765f723afd4 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -79,9 +79,16 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) if (!system_supports_fpsimd()) return; =20 - fpsimd_kvm_prepare(); - - vcpu->arch.fp_state =3D FP_STATE_HOST_OWNED; + /* + * Ensure that any host FPSIMD/SVE/SME state is saved and unbound such + * that the host kernel is responsible for restoring this state upon + * return to userspace, and the hyp code doesn't need to save anything. + * + * When the host may use SME, fpsimd_save_and_flush_cpu_state() ensures + * that PSTATE.{SM,ZA} =3D=3D {0,0}. + */ + fpsimd_save_and_flush_cpu_state(); + vcpu->arch.fp_state =3D FP_STATE_FREE; =20 vcpu_clear_flag(vcpu, HOST_SVE_ENABLED); if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) @@ -100,11 +107,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) vcpu_clear_flag(vcpu, HOST_SME_ENABLED); if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN) vcpu_set_flag(vcpu, HOST_SME_ENABLED); - - if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) { - vcpu->arch.fp_state =3D FP_STATE_FREE; - fpsimd_save_and_flush_cpu_state(); - } } } =20 --=20 2.39.5