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X-CSE-ConnectionGUID: 82A/iagQR9m7SxPvvNp1aQ== X-CSE-MsgGUID: reBlpuO5QTyKDnBXEg0QSw== X-IronPort-AV: E=McAfee;i="6700,10204,11285"; a="45258985" X-IronPort-AV: E=Sophos;i="6.12,231,1728975600"; d="scan'208";a="45258985" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Dec 2024 08:44:18 -0800 X-CSE-ConnectionGUID: Wly8Pup0TKSC6hOc/Yq/Iw== X-CSE-MsgGUID: ZsuXyWofSRGT3Ll0k6EGQQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,231,1728975600"; d="scan'208";a="96465913" Received: from philliph-desk.amr.corp.intel.com (HELO [10.124.223.121]) ([10.124.223.121]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Dec 2024 08:44:17 -0800 Message-ID: <91ebbd09-a02b-4287-a192-9259a6a78c4c@intel.com> Date: Fri, 13 Dec 2024 08:44:16 -0800 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 RFC 1/7] x86/virt/tdx: Add SEAMCALL wrapper to enter/exit TDX guest To: Adrian Hunter , pbonzini@redhat.com, seanjc@google.com, kvm@vger.kernel.org, dave.hansen@linux.intel.com Cc: rick.p.edgecombe@intel.com, kai.huang@intel.com, reinette.chatre@intel.com, xiaoyao.li@intel.com, tony.lindgren@linux.intel.com, binbin.wu@linux.intel.com, dmatlack@google.com, isaku.yamahata@intel.com, nik.borisov@suse.com, linux-kernel@vger.kernel.org, x86@kernel.org, yan.y.zhao@intel.com, chao.gao@intel.com, weijiang.yang@intel.com References: <20241121201448.36170-1-adrian.hunter@intel.com> <20241121201448.36170-2-adrian.hunter@intel.com> <0226840c-a975-42a5-9ddf-a54da7ef8746@intel.com> <56db8257-6da2-400d-8306-6e21d9af81f8@intel.com> <6af0f1c3-92eb-407e-bb19-6aeca9701e41@intel.com> Content-Language: en-US From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/13/24 08:30, Adrian Hunter wrote: > On 13/12/24 18:16, Dave Hansen wrote: >> On 12/11/24 10:43, Adrian Hunter wrote: >> ... >>> - size = tdvmcall_a0_read(vcpu); >>> - write = tdvmcall_a1_read(vcpu); >>> - port = tdvmcall_a2_read(vcpu); >>> + size = tdx->vp_enter_out.io_size; >>> + write = tdx->vp_enter_out.io_direction == TDX_WRITE; >>> + port = tdx->vp_enter_out.io_port; >> ...> + case TDVMCALL_IO: >>> + out->io_size = args.r12; >>> + out->io_direction = args.r13 ? TDX_WRITE : TDX_READ; >>> + out->io_port = args.r14; >>> + out->io_value = args.r15; >>> + break; >> >> I honestly don't understand the need for the abstracted structure to sit >> in the middle. It doesn't get stored or serialized or anything, right? >> So why have _another_ structure? >> >> Why can't this just be (for instance): >> >> size = tdx->foo.r12; >> >> ? >> >> Basically, you hand around the raw arguments until you need to use them. > > That sounds like what we have at present? That is: > > u64 tdh_vp_enter(u64 tdvpr, struct tdx_module_args *args) > { > args->rcx = tdvpr; > > return __seamcall_saved_ret(TDH_VP_ENTER, args); > } > > And then either add Rick's struct tdx_vp? Like so: > > u64 tdh_vp_enter(struct tdx_vp *vp, struct tdx_module_args *args) > { > args->rcx = tdx_tdvpr_pa(vp); > > return __seamcall_saved_ret(TDH_VP_ENTER, args); > } > > Or leave it to the caller: > > u64 tdh_vp_enter(struct tdx_module_args *args) > { > return __seamcall_saved_ret(TDH_VP_ENTER, args); > } > > Or forget the wrapper altogether, and let KVM call > __seamcall_saved_ret() ? Rick's version, please. I don't want __seamcall_saved_ret() exported to modules. I want to at least have a clean boundary beyond which __seamcall_saved_ret() is not exposed. My nit with the "u64 tdvpr" version was that there's zero type safety. The tdvp-less tdh_vp_enter() is even *less* safe of a calling convention and also requires that each caller do tdx_tdvpr_pa() or equivalent. But I feel like I'm repeating myself a bit at this point.