From patchwork Tue Mar 25 18:48:19 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 14029386 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 D6499C36008 for ; Tue, 25 Mar 2025 19:05:43 +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=dvWW4ArFGGFiWUsb1WVAzQSljuiax302A3UJxORiovw=; b=AN7T+v2UDBVjUsIT7UwNudi35p GlA4k4QLoXcZVhiTcZLPkCK47tF/Z5qPyHPZxysaox6xnYbGaRWZvE6pG7UFOm/pFHuIAE2fYFhCV Xkg0yrZyjpWvc4vyM8AnaqQIFPX5g13lxBZxemjmtIWZA+c6zYhLEr6aFD3Rxyl1MikkJw/RJ00Fb 2VsDXMQRy7tprZTkq+4xWtHxl8rSVkOFj/vAFCuopKYYGW/XXFIr9r/DZ0OoWk2b0EO0K72JltMz2 RqNNE/6itnggcwsNELL7tzbfqZ+c6PmMUqHZit3b7tU9YvO1AAGvGcKIqNt9OyUHpxFZ0R9d13uwU +LBp2cnQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1tx9ad-00000006oVt-1qnp; Tue, 25 Mar 2025 19:05:31 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.1 #2 (Red Hat Linux)) id 1tx9LQ-00000006lVz-1iQ3 for linux-arm-kernel@lists.infradead.org; Tue, 25 Mar 2025 18:49:49 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id CDF3044180; Tue, 25 Mar 2025 18:49:47 +0000 (UTC) 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 MIME-Version: 1.0 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250325_114948_502355_BC02FBBF X-CRM114-Status: GOOD ( 23.33 ) 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 | 18 ++++++++++-------- 2 files changed, 10 insertions(+), 33 deletions(-) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 3fcacbce5d427e274a9439b8a6f9edf4080d54a4..47425311acc50cae20631844806c47abff444c21 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); } -/* - * 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 ec82d0191f76717ad17a43f87bd8a806eb4ab3b8..1765f723afd493255010c71d9bd4a2ddef819565 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; - fpsimd_kvm_prepare(); - - vcpu->arch.fp_state = 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} == {0,0}. + */ + fpsimd_save_and_flush_cpu_state(); + vcpu->arch.fp_state = FP_STATE_FREE; 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 = FP_STATE_FREE; - fpsimd_save_and_flush_cpu_state(); - } } }