linux-kernel - Re: [RFC v2 11/14] arm64: Move the ASID allocator code in a separate file

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Date:   Mon, 15 Jul 2019 11:58:48 +0100
From:   Julien Grall <julien.grall@....com>
To:     James Morse <james.morse@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, marc.zyngier@....com,
        julien.thierry@....com, suzuki.poulose@....com,
        catalin.marinas@....com, will.deacon@....com
Subject: Re: [RFC v2 11/14] arm64: Move the ASID allocator code in a separate
 file

On 04/07/2019 15:56, James Morse wrote:
> Hi Julien,

Hi James,

Thank you for the review.

> 
> On 20/06/2019 14:06, Julien Grall wrote:
>> We will want to re-use the ASID allocator in a separate context (e.g
>> allocating VMID). So move the code in a new file.
>>
>> The function asid_check_context has been moved in the header as a static
>> inline function because we want to avoid add a branch when checking if the
>> ASID is still valid.
> 
>> diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
>> index 3df63a28856c..b745cf356fe1 100644
>> --- a/arch/arm64/mm/context.c
>> +++ b/arch/arm64/mm/context.c
>> @@ -23,46 +23,21 @@
> 
>> -#define ASID_FIRST_VERSION(info)	NUM_ASIDS(info)
> 
>> diff --git a/arch/arm64/lib/asid.c b/arch/arm64/lib/asid.c
>> new file mode 100644
>> index 000000000000..7252e4fdd5e9
>> --- /dev/null
>> +++ b/arch/arm64/lib/asid.c
>> @@ -0,0 +1,185 @@
> 
>> +#define ASID_FIRST_VERSION(info)	(1UL << ((info)->bits))
> 
> (oops!)

Good catch, I will fix it in the next version.

> 
> 
>> @@ -344,7 +115,7 @@ static int asids_init(void)
>>   	if (!asid_allocator_init(&asid_info, bits, ASID_PER_CONTEXT,
>>   				 asid_flush_cpu_ctxt))
>>   		panic("Unable to initialize ASID allocator for %lu ASIDs\n",
>> -		      1UL << bits);
>> +		      NUM_ASIDS(&asid_info));
> 
> Could this go in the patch that adds NUM_ASIDS()?

Actually this change is potentially wrong. This relies on asid_allocator_init() 
to set asid_info.bits even if the function fails.

So I think it would be best to keep 1UL << bits here.

Cheers,

-- 
Julien Grall