From nobody Mon Feb 9 10:27:11 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 9EC271FA177 for ; Wed, 2 Apr 2025 23:13:21 +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=1743635601; cv=none; b=MIlAEGoE9Da+LKJt8oH40l0te7A6X83HVVHy3gm7s7HO/+XOYsnxb0QgC1W4qp9VjqNm7LFlsIewZo69Fx3nMvRI24onkdfd/8+D0R3/BatQeofD+RfHIQN8uCf+PtFCApl7YSBKt43wgOzOPxwyNsethMj4CmQpXim3DkDxxic= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743635601; c=relaxed/simple; bh=snqshUSLnJbd+v3fb51JH5LHVcFkGZDOPske10wHJPE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=uaPu/KF2nqZqHxUrMSyURSHnIZCnvqkMAG8wxnYT0bTVvswOqsk8Eprg1kj1mIQRQ8ANv0dZvEonaIBe0YLUafIBvuP8ybVUSYdDEtVmPDK2uUreRUuzXNgk0qwQMeBMIfR4F3bcfqhJPp2+hDEZc8+LdvCd9jh+f9Z1ej96bn4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DuVO6/gh; 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="DuVO6/gh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C3E83C4CEE9; Wed, 2 Apr 2025 23:13:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743635601; bh=snqshUSLnJbd+v3fb51JH5LHVcFkGZDOPske10wHJPE=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=DuVO6/ghagQ+JOaEy/DNo+/nEyYFUgtfUzsfPnQrHhwSj+lXZ9UjQvmp3wExDIhX3 5WTRnFvxs0QMLKCli5aTUcD9KSrMbeqlnpoasVimHy+mjLB1Pqbc6RSmbDrUjTcKQZ Uo5V6a6n+Cz54gGgW5IBDC6WR29lbrMZLC+0dj69+g8CFJ65nBXs20w1ycC7za/z72 +mlvpxXl+3b6h9opD6j7Mid3rdRi1em8M0vAFFRPtUxIFyEB02UR4GRD1UUZzk0DEO XRokv3jgwWJ0ovE5RehrEqNr9FxnpZ+bqjfTQir47WJ15cJxU9sWT0T/PJa9OUUGTE ELtUpVW9BDc9A== From: Mark Brown Date: Wed, 02 Apr 2025 23:59:38 +0100 Subject: [PATCH 06/10] 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: <20250402-stable-sve-5-15-v1-6-84d0e5ff1102@kernel.org> References: <20250402-stable-sve-5-15-v1-0-84d0e5ff1102@kernel.org> In-Reply-To: <20250402-stable-sve-5-15-v1-0-84d0e5ff1102@kernel.org> To: Marc Zyngier , James Morse , Suzuki K Poulose , Catalin Marinas , Will Deacon , Oleg Nesterov , Oliver Upton Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, Mark Brown , 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=5038; i=broonie@kernel.org; h=from:subject:message-id; bh=Ejt+NbeaO37nvme363QMF97yG2cqvt7ZXstCZKzmrH4=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn7cR5wTTqrE8JZeGfHwq6oJBnayWjqWk7He3JmEwg F5TvL6+JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ+3EeQAKCRAk1otyXVSH0CYCB/ 9kA9vhqMVW86Hs8nEoHBbWl6JzmEE5b+D2WpzNq0s6+hSuuWhLl2yP3yWsItgovbdmroVDFpNSI7AC gzo/bVbUDT5PEzJfFBvT1UP1bu14J1vsxiq3ITVMGYWgqfNzU/WNLxXAahPpeF4fEQFtOzNS3Eeoiw GOzY5fvvUnw0pD9zRRfQZ23DTV93VF2uhJvJtCakyMXyxcaWQhRtEz9/bUh4JRGk0KwFI/XJyuLH9T I8oIF7YHOG3tnH3mzfqtN7RvRsHVdU1K3jwciY3WgfY+eCoBDqIAF+fhWG1qXP3iQU6l3ZQ0NN7fjz D1FXZlpxLtnZsI2oLa10iSceJHkJZY 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 | 13 ++++++++++--- 2 files changed, 10 insertions(+), 28 deletions(-) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index e8f10daaa0d7..4be9d9fd4fb7 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1154,31 +1154,6 @@ 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 2e0f44f4c470..2afa2521bce1 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -74,9 +74,16 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) vcpu->arch.flags &=3D ~KVM_ARM64_FP_ENABLED; vcpu->arch.flags |=3D KVM_ARM64_FP_HOST; =20 - fpsimd_kvm_prepare(); - - vcpu->arch.flags &=3D ~KVM_ARM64_HOST_SVE_ENABLED; + /* + * 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.flags &=3D ~KVM_ARM64_FP_HOST; =20 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) vcpu->arch.flags |=3D KVM_ARM64_HOST_SVE_ENABLED; --=20 2.39.5