Re: [PATCH v12 20/22] x86/virt/tdx: Allow SEAMCALL to handle #UD and #GP

[kirill . shutemov]

On Tue, Jun 27, 2023 at 02:12:50AM +1200, Kai Huang wrote:
> On the platform with the "partial write machine check" erratum, a kernel
> partial write to TDX private memory may cause unexpected machine check.
> It would be nice if the #MC handler could print additional information
> to show the #MC was TDX private memory error due to possible kernel bug.
> 
> To do that, the machine check handler needs to use SEAMCALL to query
> page type of the error memory from the TDX module, because there's no
> existing infrastructure to track TDX private pages.
> 
> SEAMCALL instruction causes #UD if CPU isn't in VMX operation.  In #MC
> handler, it is legal that CPU isn't in VMX operation when making this
> SEAMCALL.  Extend the TDX_MODULE_CALL macro to handle #UD so the
> SEAMCALL can return error code instead of Oops in the #MC handler.
> Opportunistically handles #GP too since they share the same code.
> 
> A bonus is when kernel mistakenly calls SEAMCALL when CPU isn't in VMX
> operation, or when TDX isn't enabled by the BIOS, or when the BIOS is
> buggy, the kernel can get a nicer error message rather than a less
> understandable Oops.
> 
> Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov