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

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Date:   Tue, 20 Jun 2023 13:14:36 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "Hansen, Dave" <dave.hansen@...el.com>,
        "Luck, Tony" <tony.luck@...el.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>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...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 20.06.23 12:39, Huang, Kai wrote:
> 
>>> @@ -33,12 +34,24 @@ static int __always_unused seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
>>>    				    struct tdx_module_output *out)
>>>    {
>>>    	int cpu, ret = 0;
>>> +	int retry;
>>>    	u64 sret;
>>>    
>>>    	/* Need a stable CPU id for printing error message */
>>>    	cpu = get_cpu();
>>>    
>>> -	sret = __seamcall(fn, rcx, rdx, r8, r9, out);
>>> +	/*
>>> +	 * Certain SEAMCALL leaf functions may return error due to
>>> +	 * running out of entropy, in which case the SEAMCALL should
>>> +	 * be retried.  Handle this in SEAMCALL common function.
>>> +	 *
>>> +	 * Mimic the existing rdrand_long() to retry
>>> +	 * RDRAND_RETRY_LOOPS times.
>>> +	 */
>>> +	retry = RDRAND_RETRY_LOOPS;
>>
>> Nit: I'd just do a "int retry = RDRAND_RETRY_LOOPS" and simplify this
>> comment to "Mimic rdrand_long() retry behavior."
> 
> OK will do.
> 
> But I think you are talking about replacing the second paragraph but not the
> entire comment?
>

Yes.

-- 
Cheers,

David / dhildenb