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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29FA3C433FE for ; Wed, 9 Feb 2022 16:56:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237535AbiBIQ4a (ORCPT ); Wed, 9 Feb 2022 11:56:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233407AbiBIQ43 (ORCPT ); Wed, 9 Feb 2022 11:56:29 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 83A75C0613C9 for ; Wed, 9 Feb 2022 08:56:32 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 476B0ED1; Wed, 9 Feb 2022 08:56:32 -0800 (PST) Received: from monolith.localdoman (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 12B833F73B; Wed, 9 Feb 2022 08:56:28 -0800 (PST) Date: Wed, 9 Feb 2022 16:56:48 +0000 From: Alexandru Elisei To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Andre Przywara , Christoffer Dall , Jintack Lim , Haibo Xu , Ganapatrao Kulkarni , Chase Conklin , "Russell King (Oracle)" , James Morse , Suzuki K Poulose , karl.heubaum@oracle.com, mihai.carabas@oracle.com, miguel.luis@oracle.com, kernel-team@android.com Subject: Re: [PATCH v6 31/64] KVM: arm64: nv: Only toggle cache for virtual EL2 when SCTLR_EL2 changes Message-ID: References: <20220128121912.509006-1-maz@kernel.org> <20220128121912.509006-32-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220128121912.509006-32-maz@kernel.org> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Marc, On Fri, Jan 28, 2022 at 12:18:39PM +0000, Marc Zyngier wrote: > From: Christoffer Dall > > So far we were flushing almost the entire universe whenever a VM would > load/unload the SCTLR_EL1 and the two versions of that register had > different MMU enabled settings. This turned out to be so slow that it > prevented forward progress for a nested VM, because a scheduler timer > tick interrupt would always be pending when we reached the nested VM. > > To avoid this problem, we consider the SCTLR_EL2 when evaluating if > caches are on or off when entering virtual EL2 (because this is the > value that we end up shadowing onto the hardware EL1 register). > > Signed-off-by: Christoffer Dall > Signed-off-by: Jintack Lim > Signed-off-by: Marc Zyngier > --- > arch/arm64/include/asm/kvm_mmu.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h > index 81839e9a8a24..1b314b2a69bc 100644 > --- a/arch/arm64/include/asm/kvm_mmu.h > +++ b/arch/arm64/include/asm/kvm_mmu.h > @@ -115,6 +115,7 @@ alternative_cb_end > #include > #include > #include > +#include > > void kvm_update_va_mask(struct alt_instr *alt, > __le32 *origptr, __le32 *updptr, int nr_inst); > @@ -187,7 +188,10 @@ struct kvm; > > static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu) > { > - return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101; > + if (vcpu_is_el2(vcpu)) > + return (__vcpu_sys_reg(vcpu, SCTLR_EL2) & 0b101) == 0b101; > + else > + return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101; Might be more readable if instead of 0b101 KVM would use defines, something like: static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu) { - return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101; + u64 cache_bits = SCTLR_ELx_M | SCTLR_ELx_C; + + if (vcpu_is_el2(vcpu)) + return (__vcpu_sys_reg(vcpu, SCTLR_EL2) & cache_bits) == cache_bits; + else + return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & cache_bits) == cache_bits; } Regardless, it is correct to use vcpu_read_sys_reg() for the SCTLR_EL1 case, as the most recent register value could be on the CPU in the VHE case, instead of being in memory, like it's always the case with the SCTLR_EL2 register: Reviewed-by: Alexandru Elisei Thanks, Alex > } > > static inline void __clean_dcache_guest_page(void *va, size_t size) > -- > 2.30.2 >