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([2001:b07:6468:f312:9af8:e5f5:7516:fa89]) by smtp.googlemail.com with ESMTPSA id ig2-20020a1709072e0200b00959b810efcbsm647109ejc.36.2023.05.05.01.29.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 May 2023 01:29:20 -0700 (PDT) Message-ID: <4ac6c060-8655-c5df-e27b-3dfb520ad388@redhat.com> Date: Fri, 5 May 2023 10:29:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Content-Language: en-US To: Babu Moger , richard.henderson@linaro.org Cc: weijiang.yang@intel.com, philmd@linaro.org, dwmw@amazon.co.uk, paul@xen.org, joao.m.martins@oracle.com, qemu-devel@nongnu.org, mtosatti@redhat.com, kvm@vger.kernel.org, mst@redhat.com, marcel.apfelbaum@gmail.com, yang.zhong@intel.com, jing2.liu@intel.com, vkuznets@redhat.com, michael.roth@amd.com, wei.huang2@amd.com, berrange@redhat.com, bdas@redhat.com References: <20230504205313.225073-1-babu.moger@amd.com> <20230504205313.225073-5-babu.moger@amd.com> From: Paolo Bonzini Subject: Re: [PATCH v4 4/7] target/i386: Add feature bits for CPUID_Fn80000021_EAX In-Reply-To: <20230504205313.225073-5-babu.moger@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 5/4/23 22:53, Babu Moger wrote: > Add the following feature bits. > no-nested-data-bp : Processor ignores nested data breakpoints. This bit is useless, unfortunately. Another similar bit include the one about availability of FCS/FDS in the x87 save state. They say that something is _not_ available, so a strict interpretation would prevent migrating from any old processor to Genoa, because in theory you never know if guests are using nested data breakpoints. In practice, this does not really matter because no one used them---that's why AMD could get away with removing them---but please tell the architects that while they're free to deprecate and remove old features, adding CPUID is basically pointless. Paolo