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Peter Anvin" , "Kirill A . Shutemov" , Tony Luck , Andi Kleen , linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org References: <20220415220109.282834-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20220415220109.282834-3-sathyanarayanan.kuppuswamy@linux.intel.com> From: Sathyanarayanan Kuppuswamy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/19/22 8:39 PM, Aubrey Li wrote: > On 2022/4/16 上午6:01, Kuppuswamy Sathyanarayanan wrote: >> Attestation is the process used by two un-trusted entities to prove to >> each other that it can be trusted. In TDX guest, attestation is mainly >> used to verify the trustworthiness of a TD to the 3rd party key >> servers. >> >> First step in the attestation process is to generate the TDREPORT data. >> This support is added using tdx_mcall_tdreport() API. The second stage >> in the attestation process is for the guest to request the VMM generate >> and sign a quote based on the TDREPORT acquired earlier. More details >> about the steps involved in attestation process can be found in TDX >> Guest-Host Communication Interface (GHCI) for Intel TDX 1.5, section >> titled "TD attestation" >> >> Add tdx_hcall_get_quote() helper function to implement the GetQuote >> hypercall. >> >> More details about the GetQuote TDVMCALL are in the Guest-Host >> Communication Interface (GHCI) Specification, sec 3.3, titled >> "VP.VMCALL". >> >> This will be used by the TD attestation driver in follow-on patches. >> >> Reviewed-by: Tony Luck >> Reviewed-by: Andi Kleen >> Acked-by: Kirill A. Shutemov >> Signed-off-by: Kuppuswamy Sathyanarayanan >> --- >> arch/x86/coco/tdx/tdx.c | 38 ++++++++++++++++++++++++++++++++++++++ >> arch/x86/include/asm/tdx.h | 2 ++ >> 2 files changed, 40 insertions(+) >> >> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c >> index 3e409b618d3f..c259d81a5d7f 100644 >> --- a/arch/x86/coco/tdx/tdx.c >> +++ b/arch/x86/coco/tdx/tdx.c >> @@ -21,6 +21,7 @@ >> >> /* TDX hypercall Leaf IDs */ >> #define TDVMCALL_MAP_GPA 0x10001 >> +#define TDVMCALL_GET_QUOTE 0x10002 >> >> /* MMIO direction */ >> #define EPT_READ 0 >> @@ -144,6 +145,43 @@ long tdx_mcall_tdreport(void *data, void *reportdata) >> } >> EXPORT_SYMBOL_GPL(tdx_mcall_tdreport); >> >> +/* >> + * tdx_hcall_get_quote() - Generate TDQUOTE using TDREPORT_STRUCT. >> + * >> + * @data : Address of 8KB GPA memory which contains >> + * TDREPORT_STRUCT. >> + * @len : Length of the GPA in bytes. >> + * >> + * return 0 on success or failure error number. >> + */ >> +long tdx_hcall_get_quote(void *data, u64 len) >> +{ >> + u64 ret; >> + >> + /* >> + * Use confidential guest TDX check to ensure this API is only >> + * used by TDX guest platforms. >> + */ >> + if (!data || !cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) >> + return -EINVAL; >> + >> + /* >> + * Pass the physical address of tdreport data to the VMM >> + * and trigger the tdquote generation. Quote data will be >> + * stored back in the same physical address space. More info >> + * about ABI can be found in TDX Guest-Host-Communication >> + * Interface (GHCI), sec titled "TDG.VP.VMCALL". >> + */ >> + ret = _tdx_hypercall(TDVMCALL_GET_QUOTE, cc_mkdec(virt_to_phys(data)), >> + len, 0, 0); >> + > > I commented here in v2 but no response, so let me try again. > > IIUC, virt_to_phys(data) (GPA) will be stored in the register when > TDCALL brings the context back to the VMX root mode, and hypervisor(QEMU) > will find the mapped host virtual address(HVA) with the GPA in the register, > and the subsequent ops will be HVA<->HVA in hypervisor, EPT will not be > involved so no need to cc_mkdec() this GPA. > > Please help to correct me if I was wrong. It was done to meet the expectation from VMM. For shared GPA address, VMM expects shared bit set. All cc_mkdec() does is to set this bit. > > Thanks, > -Aubrey -- Sathyanarayanan Kuppuswamy Linux Kernel Developer