Messages in this thread | | | Date | Tue, 8 Mar 2022 11:56:52 -0800 | From | Dave Hansen <> | Subject | Re: [PATCHv5 02/30] x86/tdx: Provide common base for SEAMCALL and TDCALL C wrappers |
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On 3/2/22 06:27, Kirill A. Shutemov wrote: > Secure Arbitration Mode (SEAM) is an extension of VMX architecture. It > defines a new VMX root operation (SEAM VMX root) and a new VMX non-root > operation (SEAM VMX non-root) which are both isolated from the legacy > VMX operation where the host kernel runs. > > A CPU-attested software module (called 'TDX module') runs in SEAM VMX > root to manage and protect VMs running in SEAM VMX non-root. SEAM VMX > root is also used to host another CPU-attested software module (called > 'P-SEAMLDR') to load and update the TDX module. > > Host kernel transits to either P-SEAMLDR or TDX module via the new > SEAMCALL instruction, which is essentially a VMExit from VMX root mode > to SEAM VMX root mode. SEAMCALLs are leaf functions defined by > P-SEAMLDR and TDX module around the new SEAMCALL instruction. > > A guest kernel can also communicate with TDX module via TDCALL > instruction. > > TDCALLs and SEAMCALLs use an ABI different from the x86-64 system-v ABI. > RAX is used to carry both the SEAMCALL leaf function number (input) and > the completion status (output). Additional GPRs (RCX, RDX, R8-R11) may > be further used as both input and output operands in individual leaf. > > TDCALL and SEAMCALL share the same ABI and require the largely same > code to pass down arguments and retrieve results. > > Define an assembly macro that can be used to implement C wrapper for > both TDCALL and SEAMCALL.
It's probably also worth mentioning that the SEAMCALL half won't get used in this series.
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h > index ba8042ce61c2..e5ff8ed59adf 100644 > --- a/arch/x86/include/asm/tdx.h > +++ b/arch/x86/include/asm/tdx.h > @@ -8,6 +8,33 @@ > #define TDX_CPUID_LEAF_ID 0x21 > #define TDX_IDENT "IntelTDX " > > +/* > + * SW-defined error codes. > + * > + * Bits 47:40 == 0xFF indicate Reserved status code class that never used by > + * TDX module. That's a bit clunky. Perhaps replace it with this:
* Bits 47:40 == 0xFF indicate a "Reserved" status code class that is never used by the TDX module.
> + */ > +#define TDX_ERROR (1UL << 63) > +#define TDX_SW_ERROR (TDX_ERROR | GENMASK_ULL(40, 47)) > +#define TDX_SEAMCALL_VMFAILINVALID (TDX_SW_ERROR | 0xFFFF0000ULL) > + > +#ifndef __ASSEMBLY__
The "UL" construct doesn't work in the assembler. But, this won't shoIf you use _BITUL, it will do the hard work for you.
> +/* > + * Used to gather the output registers values of the TDCALL and SEAMCALL > + * instructions when requesting services from the TDX module. > + * > + * This is a software only structure and not part of the TDX module/VMM ABI. > + */ > +struct tdx_module_output { > + u64 rcx; > + u64 rdx; > + u64 r8; > + u64 r9; > + u64 r10; > + u64 r11; > +};
With those fixed:
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
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