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Thu, 12 Dec 2024 07:42:06 -0800 (PST) X-Google-Smtp-Source: AGHT+IHsodZpbrf8J7/oaYzyqOrF+t95qa3MPBpLVtsfTFotrDy5D819vIPk3Y7tmLvjrhTY14AivA== X-Received: by 2002:a05:6000:2cf:b0:386:4332:cc99 with SMTP id ffacd0b85a97d-387888069d8mr3157708f8f.17.1734018125894; Thu, 12 Dec 2024 07:42:05 -0800 (PST) Received: from [192.168.10.27] ([151.81.118.45]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-3878248e61dsm4325250f8f.21.2024.12.12.07.42.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Dec 2024 07:42:05 -0800 (PST) Message-ID: <3b440ac3-391d-493b-9384-218bd61d7e67@redhat.com> Date: Thu, 12 Dec 2024 16:42:02 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 6/6] KVM: x86: Refactor __kvm_emulate_hypercall() into a macro To: Adrian Hunter , Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Tom Lendacky , Binbin Wu , Isaku Yamahata , Kai Huang , Xiaoyao Li , Dave Hansen References: <20241128004344.4072099-1-seanjc@google.com> <20241128004344.4072099-7-seanjc@google.com> <90577aad-552a-4cf8-a4a3-a4efcf997455@intel.com> <6423ec9d-46a2-43a3-ae9a-8e074337cd84@redhat.com> <0751a7b8-f8d3-4e27-b710-0a2bd7d06f7e@intel.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/12/24 08:32, Adrian Hunter wrote: > On 10/12/24 22:03, Sean Christopherson wrote: >> What I do deeply care about though is consistency within KVM, across vendors and >> VM flavors. And that means that guest registers absolutely need to be captured in >> vcpu->arch.regs[]. > > In general, TDX host VMM does not know what guest register > values are. > > This case, where some GPRs are passed to the host VMM via > arguments of the TDG.VP.VMCALL TDCALL, is really just a > side effect of the choice of argument passing rather than > any attempt to share guest registers with the host VMM. > > It could be regarded as more consistent to never use > vcpu->arch.regs[] for confidential guests. Yes, that's where I stand as well. There's reasons to use vcpu->arch.regs[] when "decrypted" values are available, and reasons to not use it at all. Both of them could be considered the more consistent choice, and I think I prefer slightly the latter, but it's definitely not a hill to die on... Paolo