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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0EB7C433F5 for ; Thu, 18 Nov 2021 16:28:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A6CF360F9B for ; Thu, 18 Nov 2021 16:28:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233344AbhKRQbt (ORCPT ); Thu, 18 Nov 2021 11:31:49 -0500 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:32953 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233086AbhKRQbs (ORCPT ); Thu, 18 Nov 2021 11:31:48 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=laijs@linux.alibaba.com;NM=1;PH=DS;RN=14;SR=0;TI=SMTPD_---0Uv6jhz._1637252923; Received: from 30.30.94.206(mailfrom:laijs@linux.alibaba.com fp:SMTPD_---0Uv6jhz._1637252923) by smtp.aliyun-inc.com(127.0.0.1); Fri, 19 Nov 2021 00:28:45 +0800 Message-ID: <55654594-9967-37d2-335b-5035f99212fe@linux.alibaba.com> Date: Fri, 19 Nov 2021 00:28:43 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.2.1 Subject: Re: [PATCH 13/15] KVM: SVM: Add and use svm_register_cache_reset() Content-Language: en-US To: Paolo Bonzini , Lai Jiangshan , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" References: <20211108124407.12187-1-jiangshanlai@gmail.com> <20211108124407.12187-14-jiangshanlai@gmail.com> <937c373e-80f4-38d9-b45a-a655dcb66569@redhat.com> From: Lai Jiangshan In-Reply-To: <937c373e-80f4-38d9-b45a-a655dcb66569@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/11/18 23:37, Paolo Bonzini wrote: > On 11/8/21 13:44, Lai Jiangshan wrote: >> From: Lai Jiangshan >> >> It resets all the appropriate bits like vmx. >> >> Signed-off-by: Lai Jiangshan >> --- >>   arch/x86/kvm/svm/svm.c |  3 +-- >>   arch/x86/kvm/svm/svm.h | 26 ++++++++++++++++++++++++++ >>   2 files changed, 27 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >> index b7da66935e72..ba9cfddd2875 100644 >> --- a/arch/x86/kvm/svm/svm.c >> +++ b/arch/x86/kvm/svm/svm.c >> @@ -3969,8 +3969,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) >>       svm->vmcb->control.tlb_ctl = TLB_CONTROL_DO_NOTHING; >>       vmcb_mark_all_clean(svm->vmcb); >> - >> -    kvm_register_clear_available(vcpu, VCPU_EXREG_PDPTR); >> +    svm_register_cache_reset(vcpu); >>       /* >>        * We need to handle MC intercepts here before the vcpu has a chance to >> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h >> index 0d7bbe548ac3..1cf5d5e2d0cd 100644 >> --- a/arch/x86/kvm/svm/svm.h >> +++ b/arch/x86/kvm/svm/svm.h >> @@ -274,6 +274,32 @@ static inline bool vmcb_is_dirty(struct vmcb *vmcb, int bit) >>           return !test_bit(bit, (unsigned long *)&vmcb->control.clean); >>   } >> +static inline void svm_register_cache_reset(struct kvm_vcpu *vcpu) >> +{ >> +/* >> + * SVM_REGS_AVAIL_SET - The set of registers that will be updated in cache on >> + *            demand.  Other registers not listed here are synced to >> + *            the cache immediately after VM-Exit. >> + * >> + * SVM_REGS_DIRTY_SET - The set of registers that might be outdated in >> + *            architecture. Other registers not listed here are synced >> + *            to the architecture immediately when modifying. >> + * >> + *            Special case: VCPU_EXREG_CR3 should be in this set due >> + *            to the fact.  But KVM_REQ_LOAD_MMU_PGD is always >> + *            requested when the cache vcpu->arch.cr3 is changed and >> + *            svm_load_mmu_pgd() always syncs the new CR3 value into >> + *            the architecture.  So the dirty information of >> + *            VCPU_EXREG_CR3 is not used which means VCPU_EXREG_CR3 >> + *            isn't required to be put in this set. >> + */ >> +#define SVM_REGS_AVAIL_SET    (1 << VCPU_EXREG_PDPTR) >> +#define SVM_REGS_DIRTY_SET    (0) >> + >> +    vcpu->arch.regs_avail &= ~SVM_REGS_AVAIL_SET; >> +    vcpu->arch.regs_dirty &= ~SVM_REGS_DIRTY_SET; >> +} > > I think touching regs_dirty is confusing here, so I'd go with this: It makes the code the same as vmx by clearing all the SVM_REGS_DIRTY_SET bits. And the compiler will remove this line of code since SVM_REGS_DIRTY_SET is (0), and regs_dirty is not touched. Using VMX_REGS_DIRTY_SET and SVM_REGS_DIRTY_SET and making the code similar is my intent for patch12,13. If it causes confusing, I would like to make a second thought. SVM_REGS_DIRTY_SET does be special in svm where VCPU_EXREG_CR3 is in it by definition, but it is not added into SVM_REGS_DIRTY_SET in the patch just for optimization to allow the compiler optimizes the line of code out. I'm Ok to not queue patch12,13,14. > >         vcpu->arch.regs_avail &= ~SVM_REGS_LAZY_LOAD_SET; > >         /* >          * SVM does not use vcpu->arch.regs_dirty.  The only register that >          * might be out of date in the VMCB is CR3, but KVM_REQ_LOAD_MMU_PGD >          * is always requested when the cache vcpu->arch.cr3 is changed and >          * svm_load_mmu_pgd() always syncs the new CR3 value into the VMCB. >          */ > > (VMX instead needs VCPU_EXREG_CR3 mostly because it does not want to > update it unconditionally on exit). > > Paolo