linux-kernel - Re: [PATCHv7.1 02/30] x86/tdx: Provide common base for SEAMCALL and TDCALL C wrappers

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Date:   Mon, 04 Apr 2022 15:25:23 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        bp@...en8.de
Cc:     aarcange@...hat.com, ak@...ux.intel.com, brijesh.singh@....com,
        dan.j.williams@...el.com, dave.hansen@...el.com,
        dave.hansen@...ux.intel.com, david@...hat.com, hpa@...or.com,
        jgross@...e.com, jmattson@...gle.com, joro@...tes.org,
        jpoimboe@...hat.com, knsathya@...nel.org,
        linux-kernel@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        pbonzini@...hat.com, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, sdeep@...are.com,
        seanjc@...gle.com, tglx@...utronix.de, thomas.lendacky@....com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        x86@...nel.org
Subject: Re: [PATCHv7.1 02/30] x86/tdx: Provide common base for SEAMCALL and
 TDCALL C wrappers

On Mon, 2022-04-04 at 15:19 +1200, Kai Huang wrote:
> On Mon, 2022-03-21 at 19:02 +0300, Kirill A. Shutemov wrote:
> > +/*
> > + * SW-defined error codes.
> > + *
> > + * Bits 47:40 == 0xFF indicate Reserved status code class that never used by
> > + * TDX module.
> > + */
> > +#define TDX_ERROR			_BITUL(63)
> > +#define TDX_SW_ERROR			(TDX_ERROR | GENMASK_ULL(40, 47))
> > +#define TDX_SEAMCALL_VMFAILINVALID	(TDX_SW_ERROR | _UL(0xFFFF0000))
> 
> Hi Kirill,
> 
> GENMASK_ULL(40, 47) should be GENMASK_ULL(47, 40), otherwise I am getting error
> while building TDX host code:
> 
> arch/x86/virt/vmx/tdx/tdx.c: In function ‘seamcall’:
> ./include/linux/build_bug.h:16:51: error: negative width in bit-field
> ‘<anonymous>’
>    16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> 
> Btw, perhaps you should also explicitly include <linux/bits.h> where
> GENMASK_ULL() is defined in this header file.
> 
> Btw, I previous suggested perhaps we can just use -1ULL instead of above value
> for TDX_SEAMCALL_VMFAILINVALID, but didn't get response.  The reason is this
> value will only be used when detecting P-SEAMLDR using P-SEAMLDR's SEAMLDR.INFO
> SEAMCALL.  Note your above SW-defined error codes is based on error code
> definition for TDX module, but actually P-SEAMLDR has different error code
> definition:
> 
> "The Intel P-SEAMLDR module returns error codes in the format
> 0x80000000_cccceeee, where the value cccc specifies the error class, and the
> value eeee specifies the error code within that class"
> 
> The above value happens to work for P-SEAMLDR but it doesn't follow P-SEAMLDR's
> error code definition.
> 
> More information:
> https://lore.kernel.org/lkml/20220224155630.52734-1-kirill.shutemov@linux.intel.com/T/#m5242e88e58a52a7e1da69dde3b63f19a717d3118
> 
> 

Sorry forgot to add, how TDX_SEAMCALL_VMFAILINVALID is used to detect P-SEAMLDR
and TDX module is here:

https://lore.kernel.org/lkml/cover.1647167475.git.kai.huang@intel.com/T/#m0b0896572bc79546045d03d6af65897b05ba89a4


-- 
Thanks,
-Kai