From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9AC46C433E0 for ; Wed, 17 Mar 2021 17:18:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 72C2464EE7 for ; Wed, 17 Mar 2021 17:18:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231394AbhCQRSF (ORCPT ); Wed, 17 Mar 2021 13:18:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:46412 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231382AbhCQRRo (ORCPT ); Wed, 17 Mar 2021 13:17:44 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 87EA864DDA; Wed, 17 Mar 2021 17:17:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616001464; bh=f3UV9P1ez1H29l2EmF0j0dk0b+DNBxiRJEGlA20Jt7M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qCOwbD4OrXNYihuHcVUWjgB96Cox8G+wQdO8UjpBecet6+c9mVYfBWE96NBhWa6KF N6rOyg/RIK28DWvYCjPAudJELrpnPW1bAUnQLHffda+AOY8HGbiJtvdkP2ke8H1Xrw iDYaQo27HauVEDJGrIzwEX6gwTb+qGumbdqXvjgRDpqssM8VxiCBzYBLP++jIhfbP4 iPWbrNEIQw7x9Ojg15j2CFxtbLMQGj+SweOWIkh7FqJmygEPPifeSbcmZAL8Afu481 BdeP8Ml9tx/JhvR/YwDSJL0ojBN4XRFXsyrGmJicZM8LxBiqiLu9et1MjsX9SjRdXq aFC62mSOLlFDw== Date: Wed, 17 Mar 2021 17:17:39 +0000 From: Will Deacon To: Marc Zyngier Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, dave.martin@arm.com, daniel.kiss@arm.com, Catalin Marinas , James Morse , Julien Thierry , Suzuki K Poulose , broonie@kernel.org, kernel-team@android.com Subject: Re: [PATCH 07/10] KVM: arm64: Save guest's ZCR_EL1 before saving the FPSIMD state Message-ID: <20210317171738.GA5640@willie-the-truck> References: <20210316101312.102925-1-maz@kernel.org> <20210316101312.102925-8-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210316101312.102925-8-maz@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Mar 16, 2021 at 10:13:09AM +0000, Marc Zyngier wrote: > Make sure the guest's ZCR_EL1 is saved before we save/flush the > state. This will be useful in later patches. > > Signed-off-by: Marc Zyngier > --- > arch/arm64/kvm/fpsimd.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c > index 84afca5ed6f2..b5f95abd23f5 100644 > --- a/arch/arm64/kvm/fpsimd.c > +++ b/arch/arm64/kvm/fpsimd.c > @@ -121,10 +121,10 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) > local_irq_save(flags); > > if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { > - fpsimd_save_and_flush_cpu_state(); > - > if (guest_has_sve) > __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR); > + > + fpsimd_save_and_flush_cpu_state(); I _think_ fpsimd_save_and_flush_cpu_state() contains a RDVL instruction to get at the vector length for sve_get_vl(), and this ends up reading from ZCR_EL1. So I'm not sure it's save to move it like this. Will