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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 3BA7EC4360F for ; Fri, 5 Apr 2019 11:02:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 08750217D4 for ; Fri, 5 Apr 2019 11:02:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730866AbfDELCe (ORCPT ); Fri, 5 Apr 2019 07:02:34 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:46006 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730497AbfDELCe (ORCPT ); Fri, 5 Apr 2019 07:02:34 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CA8EA168F; Fri, 5 Apr 2019 04:02:33 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2D0483F557; Fri, 5 Apr 2019 04:02:32 -0700 (PDT) Date: Fri, 5 Apr 2019 12:02:29 +0100 From: Dave Martin To: Amit Daniel Kachhap Cc: linux-arm-kernel@lists.infradead.org, Marc Zyngier , Catalin Marinas , Will Deacon , Kristina Martsenko , kvmarm@lists.cs.columbia.edu, Ramana Radhakrishnan , linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 4/9] KVM: arm/arm64: preserve host HCR_EL2 value Message-ID: <20190405110229.GR3567@e103592.cambridge.arm.com> References: <1554172037-4516-1-git-send-email-amit.kachhap@arm.com> <1554172037-4516-5-git-send-email-amit.kachhap@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1554172037-4516-5-git-send-email-amit.kachhap@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 02, 2019 at 07:57:12AM +0530, Amit Daniel Kachhap wrote: > From: Mark Rutland > > When restoring HCR_EL2 for the host, KVM uses HCR_HOST_VHE_FLAGS, which > is a constant value. This works today, as the host HCR_EL2 value is > always the same, but this will get in the way of supporting extensions > that require HCR_EL2 bits to be set conditionally for the host. > > To allow such features to work without KVM having to explicitly handle > every possible host feature combination, this patch has KVM save/restore > for the host HCR when switching to/from a guest HCR. The saving of the > register is done once during cpu hypervisor initialization state and is > just restored after switch from guest. > > For fetching HCR_EL2 during kvm initialisation, a hyp call is made using > kvm_call_hyp and is helpful in non-VHE case. > > For the hyp TLB maintenance code, __tlb_switch_to_host_vhe() is updated > to toggle the TGE bit with a RMW sequence, as we already do in > __tlb_switch_to_guest_vhe(). > > The value of hcr_el2 is now stored in struct kvm_cpu_context as both host > and guest can now use this field in a common way. > > Signed-off-by: Mark Rutland > [Added cpu_init_host_ctxt, hcr_el2 field in struct kvm_cpu_context, > save hcr_el2 in hyp init stage] > Signed-off-by: Amit Daniel Kachhap > Reviewed-by: James Morse > Cc: Marc Zyngier > Cc: Christoffer Dall > Cc: kvmarm@lists.cs.columbia.edu [...] > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index a01fe087..3b09fd0 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -209,6 +209,8 @@ struct kvm_cpu_context { > u32 copro[NR_COPRO_REGS]; > }; > > + /* HYP host/guest configuration */ > + u64 hcr_el2; Minor nit: You could delete "host/guest" from the comment here. This is implied by the fact that the member is in struct kvm_cpu_context in the first place. > struct kvm_vcpu *__hyp_running_vcpu; > }; [...] > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c > index 3563fe6..f5cefa1 100644 > --- a/arch/arm64/kvm/hyp/switch.c > +++ b/arch/arm64/kvm/hyp/switch.c [...] > @@ -159,9 +159,10 @@ static void deactivate_traps_vhe(void) > } > NOKPROBE_SYMBOL(deactivate_traps_vhe); > > -static void __hyp_text __deactivate_traps_nvhe(void) > +static void __hyp_text __deactivate_traps_nvhe(struct kvm_cpu_context *host_ctxt) Where __hyp_text functions accept pointer arguments, they are usually hyp pointers already... (see below) > { > u64 mdcr_el2 = read_sysreg(mdcr_el2); > + struct kvm_cpu_context *hyp_host_ctxt = kern_hyp_va(host_ctxt); > > __deactivate_traps_common(); > > @@ -169,25 +170,28 @@ static void __hyp_text __deactivate_traps_nvhe(void) > mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT; > > write_sysreg(mdcr_el2, mdcr_el2); > - write_sysreg(HCR_HOST_NVHE_FLAGS, hcr_el2); > + write_sysreg(hyp_host_ctxt->hcr_el2, hcr_el2); > write_sysreg(CPTR_EL2_DEFAULT, cptr_el2); > } > > static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu) > { > + struct kvm_cpu_context *host_ctxt; > + > + host_ctxt = vcpu->arch.host_cpu_context; host_ctxt is not otherwise used here, so can we convert it up-front so that the argument to __deactivate_traps_nvhe() and deactivate_traps_vhe() is a hyp pointer already? So: struct kvm_cpu_context *hyp_host_ctxt; hyp_host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > /* > * If we pended a virtual abort, preserve it until it gets > * cleared. See D1.14.3 (Virtual Interrupts) for details, but > * the crucial bit is "On taking a vSError interrupt, > * HCR_EL2.VSE is cleared to 0." > */ > - if (vcpu->arch.hcr_el2 & HCR_VSE) > - vcpu->arch.hcr_el2 = read_sysreg(hcr_el2); > + if (vcpu->arch.ctxt.hcr_el2 & HCR_VSE) > + vcpu->arch.ctxt.hcr_el2 = read_sysreg(hcr_el2); > > if (has_vhe()) > - deactivate_traps_vhe(); > + deactivate_traps_vhe(host_ctxt); > else > - __deactivate_traps_nvhe(); > + __deactivate_traps_nvhe(host_ctxt); Then just pass hyp_host_ctxt to both of these, and drop the kern_hyp_va() conversion from __deactivate_traps_nvhe(). This may be a bit less confusing. Alternatively, just pass in the vcpu pointer (since this pattern is already well established all over the place). Another option could be to pull the hcr_el2 write out of the backends entirely and put it in this common code instead. This doesn't look straightforward though (or at least, I don't remember enough about how all these traps handling functions fit together...) [...] Cheers ---Dave