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 4DAB6C433DB for ; Wed, 17 Mar 2021 17:58:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D95064F17 for ; Wed, 17 Mar 2021 17:58:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230411AbhCQR5x (ORCPT ); Wed, 17 Mar 2021 13:57:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:41372 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232746AbhCQR5k (ORCPT ); Wed, 17 Mar 2021 13:57:40 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7E07664F0F; Wed, 17 Mar 2021 17:57:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616003860; bh=KLrz/zlZvv0deqnTNA4E5YrAwOuKGvg1QIpXtpi+EK0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BY8USoWjrrilAobRONwMs0Nq33hyLtCVksyL4S7NKSyHLT6U/f2Xa3IslxnTdhD07 cQ6QnOEJlaNLL21vzJ3pgocSZuNvsj0/VKXWFTuJbdUuVVNZcwbDy2KYym4GRIBlfd xzMtrcyqT0ww4WtZ8THMiLnJAw2EeMosVV584bglsTQBSZhmiH+VvfwBLw4vLDiTPi j7Tws89nEtSJZtqUE6aVbC8hv7gNHKUMJNYECw8+88A7rQr3b260WD1LbSFHT5c9Fq rJbLuRDKKRHE78Sv+j2Btar3gYfMyfRuor76510v1pcsX1OUj8+ypsW9OiVlvhjR9N PLqFOTfhZhTFQ== Date: Wed, 17 Mar 2021 17:57:35 +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 09/10] KVM: arm64: Save/restore SVE state for nVHE Message-ID: <20210317175734.GA5713@willie-the-truck> References: <20210316101312.102925-1-maz@kernel.org> <20210316101312.102925-10-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210316101312.102925-10-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 10:13:11AM +0000, Marc Zyngier wrote: > Implement the SVE save/restore for nVHE, following a similar > logic to that of the VHE implementation: > > - the SVE state is switched on trap from EL1 to EL2 > > - no further changes to ZCR_EL2 occur as long as the guest isn't > preempted or exit to userspace > > - on vcpu_put(), ZCR_EL2 is reset to its default value, and ZCR_EL1 > restored to the default guest value > > Signed-off-by: Marc Zyngier > --- > arch/arm64/kvm/fpsimd.c | 15 ++++++++-- > arch/arm64/kvm/hyp/include/hyp/switch.h | 37 +++++++++---------------- > arch/arm64/kvm/hyp/nvhe/switch.c | 4 +-- > 3 files changed, 28 insertions(+), 28 deletions(-) > > diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c > index b5f95abd23f5..cc6cdea69596 100644 > --- a/arch/arm64/kvm/fpsimd.c > +++ b/arch/arm64/kvm/fpsimd.c > @@ -121,11 +121,22 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) > local_irq_save(flags); > > if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { > - if (guest_has_sve) > + if (guest_has_sve) { > __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR); > > + /* Restore the VL that was saved when bound to the CPU */ > + if (!has_vhe()) { > + u64 zcr; > + > + kvm_call_hyp(__kvm_reset_sve_vq); What would go wrong if we did this unconditionally on return to the host, or is it just a performance thing to move work off the fast path where we return back to the same vCPU? Will