linux-kernel - Re: [PATCH 20/30] x86, mm: remove hard-coded ASID limit checks

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Message-ID: <52465ada-a7e9-ccb3-e946-5a7c8a0476c5@linux.intel.com>
Date:   Fri, 10 Nov 2017 10:41:26 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        moritz.lipp@...k.tugraz.at, daniel.gruss@...k.tugraz.at,
        michael.schwarz@...k.tugraz.at, richard.fellner@...dent.tugraz.at,
        luto@...nel.org, torvalds@...ux-foundation.org,
        keescook@...gle.com, hughd@...gle.com, x86@...nel.org
Subject: Re: [PATCH 20/30] x86, mm: remove hard-coded ASID limit checks

On 11/10/2017 04:20 AM, Peter Zijlstra wrote:
> On Wed, Nov 08, 2017 at 11:47:24AM -0800, Dave Hansen wrote:
>> +#define CR3_HW_ASID_BITS 12
>> +#define NR_AVAIL_ASIDS ((1<<CR3_AVAIL_ASID_BITS) - 1)
> That evaluates to 4095
> 
>> -		VM_WARN_ON_ONCE(asid > 4094);
>> +		VM_WARN_ON_ONCE(asid > NR_AVAIL_ASIDS);
> Not the same number

I think this got fixed up in the next patch (the check becomes a >=),
but I'll fix this to make it more clean and fix the intermediate breakage.