linux-kernel - Re: [PATCH 2/2] xen: rename wrong named pfn related variables

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Date:   Wed, 16 Jun 2021 12:43:22 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <jbeulich@...e.com>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 2/2] xen: rename wrong named pfn related variables

On 16.06.21 11:56, Jan Beulich wrote:
> On 16.06.2021 09:30, Juergen Gross wrote:
>> --- a/arch/x86/xen/p2m.c
>> +++ b/arch/x86/xen/p2m.c
>> @@ -95,8 +95,8 @@ unsigned long *xen_p2m_addr __read_mostly;
>>   EXPORT_SYMBOL_GPL(xen_p2m_addr);
>>   unsigned long xen_p2m_size __read_mostly;
>>   EXPORT_SYMBOL_GPL(xen_p2m_size);
>> -unsigned long xen_max_p2m_pfn __read_mostly;
>> -EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
>> +unsigned long xen_p2m_max_size __read_mostly;
>> +EXPORT_SYMBOL_GPL(xen_p2m_max_size);
> 
> Instead of renaming the exported variable (which will break consumers
> anyway), how about dropping the apparently unneeded export at this
> occasion?

Why do you think it isn't needed? It is being referenced via the inline
function __pfn_to_mfn() in arch/x86/include/asm/xen/page.h. And
__pfn_to_mfn() is used via lots of other inline functions and macros.

> Further it looks to me as if xen_p2m_size and this variable
> were actually always kept in sync, so I'd like to put up the question
> of dropping one of the two.

Hmm, should be possible, yes.

> 
>> @@ -121,7 +121,7 @@ static pte_t *p2m_identity_pte;
>>    * can avoid scanning the whole P2M (which may be sized to account for
>>    * hotplugged memory).
>>    */
>> -static unsigned long xen_p2m_last_pfn;
>> +static unsigned long xen_p2m_pfn_limit;
> 
> As to the comment remark in patch 1: You don't alter the comment
> here either, and "limit" still doesn't make clear whether that's an
> inclusive or exclusive limit.

Oh, indeed. Will fix that.


Juergen

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