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Wed, 27 Nov 2024 10:16:01 -0800 (PST) X-Google-Smtp-Source: AGHT+IGlSOETqY5xWikoXdGyx+ENqCPhG3pAdQ1oFPlJH7WCPfJ43PWFxdmZZG2nmMbq+n4dBvEiQg== X-Received: by 2002:a05:600c:1c93:b0:434:a852:ba77 with SMTP id 5b1f17b1804b1-434a9dcec68mr46330345e9.15.1732731361607; Wed, 27 Nov 2024 10:16:01 -0800 (PST) Received: from [192.168.10.3] ([151.49.236.146]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-434aa7fa1dasm28287285e9.42.2024.11.27.10.16.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Nov 2024 10:16:01 -0800 (PST) Message-ID: <0835f21a-c0b1-429c-a107-d7d0a2838194@redhat.com> Date: Wed, 27 Nov 2024 19:15:59 +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: [RFC PATCH 1/6] x86/virt/tdx: Add SEAMCALL wrappers for TDX KeyID management To: "Edgecombe, Rick P" , "Hansen, Dave" , "seanjc@google.com" Cc: "yuan.yao@intel.com" , "Huang, Kai" , "x86@kernel.org" , "binbin.wu@linux.intel.com" , "Li, Xiaoyao" , "linux-kernel@vger.kernel.org" , "Zhao, Yan Y" , "tony.lindgren@linux.intel.com" , "kvm@vger.kernel.org" , "Yamahata, Isaku" , "isaku.yamahata@gmail.com" , "Hunter, Adrian" References: <20241115202028.1585487-1-rick.p.edgecombe@intel.com> <20241115202028.1585487-2-rick.p.edgecombe@intel.com> <30d0cef5-82d5-4325-b149-0e99833b8785@intel.com> <6903d890-c591-4986-8c88-a4b069309033@intel.com> <92547c5fea8d47cc351afa241cf8b5e5999dbe28.camel@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: 8bit On 11/23/24 03:06, Edgecombe, Rick P wrote: > On Fri, 2024-11-22 at 16:08 -0800, Dave Hansen wrote: >> On 11/22/24 15:55, Sean Christopherson wrote: >>> On Fri, Nov 22, 2024, Dave Hansen wrote: >>> I don't know the full context, but working with "struct page" is a pain when every >>> user just wants the physical address.  KVM SVM had a few cases where pointers were >>> tracked as "struct page", and it was generally unpleasant to read and work with. >> >> I'm not super convinced. page_to_phys(foo) is all it takes >> >>> I also don't like conflating the kernel's "struct page" with the architecture's >>> definition of a 4KiB page. >> >> That's fair, although it's pervasively conflated across our entire >> codebase. But 'struct page' is substantially better than a hpa_t, >> phys_addr_t or u64 that can store a full 64-bits of address. Those >> conflate a physical address with a physical page, which is *FAR* worse. > > In the case of tdh_mem_page_aug(), etc the caller only has a kvm_pfn_t passed > from a TDP MMU callback, for the page to be mapped in the guest TD. It is > probably not nice to assume that this kvm_pfn_t will have a struct page. So we > shouldn't always use struct pages for the SEAMCALL wrappers in any case. > > What if we just move these members from hpa_t to pfn_t? It keeps us off struct > page, but addresses some of Dave's concerns about hpa_t looking like a specific > address. For tdr I agree with Dave that you probably want a struct which stores the struct page*. Currently the code is using __get_free_page(), but it's a small change to have it use alloc_page() instead, and __free_page() instead of free_page(). The only difference on the arch/x86/virt/ side is a bunch of added page_to_phys(). Anyhow, whatever you post I'll take care of adjusting in the KVM patches. Paolo