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([2001:b07:6468:f312:1cb4:2b36:6750:73ce]) by smtp.gmail.com with ESMTPSA id f123sm4155582wmf.44.2020.05.09.06.28.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 09 May 2020 06:28:44 -0700 (PDT) Subject: Re: [PATCH v2 8/9] KVM: x86, SVM: isolate vcpu->arch.dr6 from vmcb->save.dr6 To: Peter Xu Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20200507115011.494562-1-pbonzini@redhat.com> <20200507115011.494562-9-pbonzini@redhat.com> <20200507192808.GK228260@xz-x1> <20200508153210.GZ228260@xz-x1> From: Paolo Bonzini Message-ID: Date: Sat, 9 May 2020 15:28:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200508153210.GZ228260@xz-x1> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/05/20 17:32, Peter Xu wrote: > On Fri, May 08, 2020 at 12:33:57AM +0200, Paolo Bonzini wrote: >> On 07/05/20 21:28, Peter Xu wrote: >>>> - svm->vcpu.arch.dr6 = dr6; >>>> + WARN_ON(svm->vcpu.arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT); >>>> + svm->vcpu.arch.dr6 &= ~(DR_TRAP_BITS | DR6_RTM); >>>> + svm->vcpu.arch.dr6 |= dr6 & ~DR6_FIXED_1; >>> I failed to figure out what the above calculation is going to do... >> >> The calculation is merging the cause of the #DB with the guest DR6. >> It's basically the same effect as kvm_deliver_exception_payload. > > Shall we introduce a helper for both kvm_deliver_exception_payload and here > (e.g. kvm_merge_dr6)? Also, wondering whether this could be a bit easier to > follow by defining: It would make sense indeed but I plan to get rid of this in 5.9 (so in about a month), as explained in the comment. Paolo