Re: [PATCH v11 06/20] x86/virt/tdx: Handle SEAMCALL running out of entropy error

[Huang, Kai]

On Fri, 2023-06-09 at 17:42 +0300, Nikolay Borisov wrote:
> 
> On 4.06.23 г. 17:27 ч., Kai Huang wrote:
> > Certain SEAMCALL leaf functions may return error due to running out of
> > entropy, in which case the SEAMCALL should be retried as suggested by
> > the TDX spec.
> > 
> > Handle this case in SEAMCALL common function.  Mimic the existing
> > rdrand_long() to retry RDRAND_RETRY_LOOPS times.
> > 
> > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> > ---
> > 
> > v10 -> v11:
> >   - New patch
> > 
> > ---
> >   arch/x86/virt/vmx/tdx/tdx.c | 15 ++++++++++++++-
> >   arch/x86/virt/vmx/tdx/tdx.h | 17 +++++++++++++++++
> >   2 files changed, 31 insertions(+), 1 deletion(-)
> > 
> 
> <snip>
> 
> > diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> > index 48ad1a1ba737..55dbb1b8c971 100644
> > --- a/arch/x86/virt/vmx/tdx/tdx.h
> > +++ b/arch/x86/virt/vmx/tdx/tdx.h
> > @@ -4,6 +4,23 @@
> >   
> >   #include <linux/types.h>
> >   
> > +/*
> > + * This file contains both macros and data structures defined by the TDX
> > + * architecture and Linux defined software data structures and functions.
> > + * The two should not be mixed together for better readability.  The
> > + * architectural definitions come first.
> > + */
> > +
> > +/*
> > + * TDX SEAMCALL error codes
> > + */
> > +#define TDX_RND_NO_ENTROPY	0x8000020300000000ULL
> 
> Where is this return value documented, in TDX module 1.0 spec there are 
> only: 8000020[123]00000000 specified and there's 80000800 
> (TDX_KEY_GENERATION_FAILED) and its description mentions the possible 
> failure due to lack of entropy?
> 

It's documented in TDX module V1.5 ABI Specification:

https://cdrdv2.intel.com/v1/dl/getContent/733579

The later versions of TDX module try to use TDX_RND_NO_ENTROPY to cover all
errors due to running out of entropy, but TDX module 1.0 for now doesn't.

This patch aims to resolve this error code in the common code.