From patchwork Wed Apr 2 23:20:21 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 14036605 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 AC91AC36018 for ; Wed, 2 Apr 2025 23:47:17 +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:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=f1HjBXlklLcdesQqC3h2XM3HL2gCYP/Vt59GYna5i34=; b=Q6DjXNpafkccBIgbQdfci9p+Yx 4X7j2EcW8B/2Pn37x9jUZy7jo+VDrhLxDsI9Z/zbTIhl3h/Ma3jx0vk2T9xHn64IpF3xwD7hsEi6q d38FF3thm/fKGOV1Awm2hudTIgsIYQZeeMDE3oGQ52jDUfyRNj+qi9FyTTpWXXsTgjS14sdz8/4gY eVpKFFfxClqD9zGmpNR32WEJTWXt0Bc0JuOSFFKBwe/CFbaFV1kLCavOPEs7AJu9g40t68jioPHxT RJg5XGXctRAHGTa3UOmUzy3EIT+oVSkil121I/fSJSfM5bBWydg7iXNKc9oJ1VvPJc+uS/gYi/V1s ZxXIzaCw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1u07nX-00000007Rdc-1v6L; Wed, 02 Apr 2025 23:47:07 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.98.1 #2 (Red Hat Linux)) id 1u07OZ-00000007OKO-0G6X for linux-arm-kernel@lists.infradead.org; Wed, 02 Apr 2025 23:21:21 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 8219E5C6BDE; Wed, 2 Apr 2025 23:19:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE1E6C4CEE7; Wed, 2 Apr 2025 23:21:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743636078; bh=snqshUSLnJbd+v3fb51JH5LHVcFkGZDOPske10wHJPE=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=sYGz9gb8KvpUa0HRhYguwB4hB7vsGD6TFwdy1A6/y9HWe577AlLr/4GMPukRll73I NM0/2OFYEHf2Jcg8FbrvICNVM0NLIVUNFtpiAnOu+artKbM1hKv9KN0772NeMDhf43 s5iWSDUl4AWcjtF8nrYl2jImsoxHGMaYmc5DaT9Z+jxtXWvPF9GhGLLK1ntu9AdnkY HAGa/RoM8p34OLgaXbsdwIctrQ2uV+2uBRMG/ZApi9q7GOYxH7XgZ7gBIMPmvFIyNS iE7WRRhcXqrZ977s0R5NDFteZ5jeWF7H2KYt08VLtKD3OiJGWRqiOUBeU4IaOWHvF3 rCW8JtxgM3FEg== From: Mark Brown Date: Thu, 03 Apr 2025 00:20:21 +0100 Subject: [PATCH 5.15 v2 06/10] KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state MIME-Version: 1.0 Message-Id: <20250403-stable-sve-5-15-v2-6-30a36a78a20a@kernel.org> References: <20250403-stable-sve-5-15-v2-0-30a36a78a20a@kernel.org> In-Reply-To: <20250403-stable-sve-5-15-v2-0-30a36a78a20a@kernel.org> To: Greg Kroah-Hartman , 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, stable@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/pANAwAKASTWi3JdVIfQAcsmYgBn7cZQ5tm40r2b1bQwOm8gKwP9zN48IXcL9X/uX0Uk D8BCtDiJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ+3GUAAKCRAk1otyXVSH0O0qB/ 9DjzWrqHB/ealFHrbJx8rz9CXccHjmcW/dORk40oI1WpFeLrzr6IaxvIZtKwcPS5+a4l6TC41Zwuc0 V88PmFA4zDte1ZaTgJrnqmiPxyPhF+zXfyb/MP1cciCpbW1/NHpM25CHJCiqj9Nl6WaQFao55wDYUT Kg6YYC9ELYlWOZJnS/64wmAb56X4y/WOnqPSXn8m3RVeJdcDQR7J32nq0sV+MFOq+dRvY+AT3iFFXy +hWcD97P1ZtO5oAPid+S0LJZTFoXoDzNTKF5ev859GOX3kUOBPdZEaSafUlsNzPiszuYf2gtCJi4Sc 8v7R6uKy9ra8aZqklfcnfgUVJqrCgu X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250402_162119_177709_E9BB4D71 X-CRM114-Status: GOOD ( 23.87 ) 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 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 state. * 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 KVM 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.com 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); } -/* - * 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 = 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 &= ~KVM_ARM64_FP_ENABLED; vcpu->arch.flags |= KVM_ARM64_FP_HOST; - fpsimd_kvm_prepare(); - - vcpu->arch.flags &= ~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} == {0,0}. + */ + fpsimd_save_and_flush_cpu_state(); + vcpu->arch.flags &= ~KVM_ARM64_FP_HOST; if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;