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

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Date:   Mon, 12 Jun 2023 11:04:49 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "n.borisov.lkml@...il.com" <n.borisov.lkml@...il.com>
CC:     "Hansen, Dave" <dave.hansen@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Luck, Tony" <tony.luck@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v11 06/20] x86/virt/tdx: Handle SEAMCALL running out of
 entropy error

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@...el.com>
> > ---
> > 
> > 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.