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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id c28sm2473420ejc.102.2021.07.09.09.58.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Jul 2021 09:58:54 -0700 (PDT) Subject: Re: [PATCH] KVM: X86: Also reload the debug registers before kvm_x86->run() when the host is using them To: Jim Mattson Cc: Lai Jiangshan , Lai Jiangshan , linux-kernel@vger.kernel.org, Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org References: <20210628172632.81029-1-jiangshanlai@gmail.com> <46e0aaf1-b7cd-288f-e4be-ac59aa04908f@redhat.com> <397a448e-ffa7-3bea-af86-e92fbb273a07@redhat.com> <01946b5a-9912-3dfb-36f0-031f425432d2@redhat.com> From: Paolo Bonzini Message-ID: Date: Fri, 9 Jul 2021 18:58:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/07/21 18:35, Jim Mattson wrote: >>>> Just what you said, it's not easy and the needs are limited. I >>>> implemented kvm_vcpu_check_breakpoint because I was interested in >>>> using hardware breakpoints from gdb, even with unrestricted_guest=0 >>>> and invalid guest state, but that's it. >>> It seems kvm_vcpu_check_breakpoint() handles only for code breakpoint >>> and doesn't handle for data breakpoints. >> Correct, there's a comment above the call. But data breakpoint are much >> harder and relatively less useful. > > Data breakpoints are actually quite useful. I/O breakpoints not so much. Normally yes; much less for the specific case of debugging invalid-guest-state or other invocations of the emulator. Paolo