From nobody Mon Feb 9 16:45:24 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 CD1FC1F8BCA; Tue, 25 Mar 2025 18:49:39 +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=1742928579; cv=none; b=Yzk5vWq11l9LAFva6by+HgmZIbsaepDCOQS4QlwmteqNOPDV1TceLo4ZOOn8lazsBbz1Nr/Pt24YNuo8YVsQPwXTtfFETWs8Lbu0H3V2Wi4KU+qNZrNagvLS0PN9gDTF8gX/Q8fxBlhy3BCHIb1DKBjrbGrSBNxfTLi0ODYiIqQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742928579; c=relaxed/simple; bh=kF90/tmjiDpKHRLxjaWx89TWs7XEkPUTq8acak0W17k=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=iw1TH/tukbDEa333qLkp7/uFg/QPgoaBewi9UEV9YbIC44GXGt39mPGTZEqn6hGXcmDz0phfPq6nzL7u6iNpM2XZEK+IVRzBtJZLJqq6AxCxYOIA+M3zoBI0n8NIRisVSpFWZqmvZN2kRunt+BcalYYFZJAracD6poF/QVzYHtE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lR4IS2Or; 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="lR4IS2Or" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1DF56C4CEE8; Tue, 25 Mar 2025 18:49:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742928579; bh=kF90/tmjiDpKHRLxjaWx89TWs7XEkPUTq8acak0W17k=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=lR4IS2OrAOIGHd9vQfvzFGdDSM2vZPPt/Ysn6xh3MralbAnmY8/W2bQeiH5glLBvf evkMT+LdMHruuxaRoFNiXDBsjjKEx6WrxzWegRB1H/IsDmL0e4E+1gcOt68ptjr1Ma UJ+rfT1jn+VaNh+Qy+QUpTub6IGe1UydIQ3vUNwye56hUBVgprRH+Zi7G6MRwtxd4V kb8Z17fEpwwVMcZj3JT60wXAzNNvd+O+SHtz2tFoQuSctFev1sMTEEeytsmuIU7Q9R UhzVFSzF9eAnDvWd36q7+JPO74AxiHo/nIs51HKpAd2YaRFnDJ7/XYA1jSzI1Nyjgl SpQ5Iem8/OAvw== From: Mark Brown Date: Tue, 25 Mar 2025 18:48:19 +0000 Subject: [PATCH 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: <20250325-stable-sve-6-1-v1-5-83259d427d84@kernel.org> References: <20250325-stable-sve-6-1-v1-0-83259d427d84@kernel.org> In-Reply-To: <20250325-stable-sve-6-1-v1-0-83259d427d84@kernel.org> To: Catalin Marinas , Will Deacon , Marc Zyngier , James Morse , Suzuki K Poulose , Oliver Upton , Oleg Nesterov Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, Mark Brown , Mark Rutland , Eric Auger , Wilco Dijkstra , Eric Auger , Florian Weimer , Fuad Tabba , Jeremy Linton , Paolo Bonzini X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=5482; i=broonie@kernel.org; h=from:subject:message-id; bh=ewzn5IP4VkbMj71S15BmY2zHbEEloXp7AxOn501I1yU=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn4vqpb/8Uw9L4ET+4uOu5wSGAfJs5SlAjNDckuZRJ 2gScMKKJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ+L6qQAKCRAk1otyXVSH0Fo7B/ 9SKP6rqOcAMjzdH5ikG6gfvznZiS/xfVHaalOqB1Buwk0I6zyrFe2tq/2pNY8qADJwiolKZfChrAIj NdLVlJqlTCGK3nQJdemHllgPkfQaoPeAipgPaTeEVDCF9CDJ5gayybDBLPjpo2xKqOZnO2SjFW+lZa oevQKR1y0SVHhdUfq9G6ryap1xmvaQfWw/jv9EqiMzhAi0OOBCBFXu9lJv1cV3BMOA3N3k4Y7eyWRd Q0j5OWH+0jvSAgbsQP4UA6UObD7q0bCrx7M6W/J2SNcfvplMuxZGoFK1AAm5fAIntF9OdnvOrxg7aZ arbikbwrEyL62qvZEa7RpNo3W7b3f0 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 3fcacbce5d427e274a9439b8a6f9edf4080d54a4..47425311acc50cae20631844806= c47abff444c21 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 ec82d0191f76717ad17a43f87bd8a806eb4ab3b8..1765f723afd493255010c71d9bd= 4a2ddef819565 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