From mboxrd@z Thu Jan 1 00:00:00 1970 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 65C6525E812; Tue, 25 Mar 2025 12:40:48 +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=1742906448; cv=none; b=KscCJkYue1xcn1Ea0N1yNv05R5HxmwVzuXGE2YMuWp+LK2V7HcFWKZhs+007yiR/03PyjzQQMCrefSve3MS022cJ8VQkmQ//98lsody9AhHMau6NR8FvDgjEpoZVyZwC9WDcMzlygs2Hwc5JSL0+19tRZVxEYRVjs+yYt/mKg04= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742906448; c=relaxed/simple; bh=ehCzbG2HmZDSMjoQW3MhgqT4hwnB0Lpr7LQqmxsXyLM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=R4UqU5nlVjSiorsb4WEUZiNZocwgC+RVW0C0Kke466HUxk966Tf5/fVnen4zWBMDoT8G4AmVMWBiF3p+O5kBLX6LWu3jw1VFzI7ADvk4701bzefR7vyjlTUJ5YdcnLmT8B1k2eiAKJOYoLIIibv6zNEcSs8RZzSGnDhfWgAliHg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=GbnMhNBo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="GbnMhNBo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02E85C4CEE9; Tue, 25 Mar 2025 12:40:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742906448; bh=ehCzbG2HmZDSMjoQW3MhgqT4hwnB0Lpr7LQqmxsXyLM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GbnMhNBoe5e9c6K3ncDSqBtooNr5uXOOMOfe2nPr3yJI3G4TbNPATvz9vBcmBaEA7 MdCbGAKTiEX8pBRLThVV7fLIfeWguKcLBTeqZYTT5UTDvMjo77RRwfQ3jncZ2c289I ToQ76Ii6KXNKGlNOtsT3jImmJAuZMYoU0dcIQSeI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Auger , Wilco Dijkstra , Mark Brown , Eric Auger , Will Deacon , Catalin Marinas , Florian Weimer , Fuad Tabba , Jeremy Linton , Marc Zyngier , Oliver Upton , Paolo Bonzini , Mark Rutland Subject: [PATCH 6.12 105/116] KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state Date: Tue, 25 Mar 2025 08:23:12 -0400 Message-ID: <20250325122151.892491053@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250325122149.207086105@linuxfoundation.org> References: <20250325122149.207086105@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ 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 ] Signed-off-by: Mark Rutland Signed-off-by: Mark Brown Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/fpsimd.c | 25 ------------------------- arch/arm64/kvm/fpsimd.c | 35 ++++++++++------------------------- 2 files changed, 10 insertions(+), 50 deletions(-) --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1695,31 +1695,6 @@ void fpsimd_signal_preserve_current_stat } /* - * 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 * this function. --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -54,16 +54,18 @@ void kvm_arch_vcpu_load_fp(struct kvm_vc if (!system_supports_fpsimd()) return; - fpsimd_kvm_prepare(); - /* - * We will check TIF_FOREIGN_FPSTATE just before entering the - * guest in kvm_arch_vcpu_ctxflush_fp() and override this to - * FP_STATE_FREE if the flag set. + * 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}. */ - *host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED; - *host_data_ptr(fpsimd_state) = kern_hyp_va(¤t->thread.uw.fpsimd_state); - *host_data_ptr(fpmr_ptr) = kern_hyp_va(¤t->thread.uw.fpmr); + fpsimd_save_and_flush_cpu_state(); + *host_data_ptr(fp_owner) = FP_STATE_FREE; + *host_data_ptr(fpsimd_state) = NULL; + *host_data_ptr(fpmr_ptr) = NULL; vcpu_clear_flag(vcpu, HOST_SVE_ENABLED); if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) @@ -73,23 +75,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vc vcpu_clear_flag(vcpu, HOST_SME_ENABLED); if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN) vcpu_set_flag(vcpu, HOST_SME_ENABLED); - - /* - * If PSTATE.SM is enabled then save any pending FP - * state and disable PSTATE.SM. If we leave PSTATE.SM - * enabled and the guest does not enable SME via - * CPACR_EL1.SMEN then operations that should be valid - * may generate SME traps from EL1 to EL1 which we - * can't intercept and which would confuse the guest. - * - * Do the same for PSTATE.ZA in the case where there - * is state in the registers which has not already - * been saved, this is very unlikely to happen. - */ - if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) { - *host_data_ptr(fp_owner) = FP_STATE_FREE; - fpsimd_save_and_flush_cpu_state(); - } } /*