linux-kernel - Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page

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Date:   Fri, 31 Jan 2020 17:15:20 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Segher Boessenkool <segher@...nel.crashing.org>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page



Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
> On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
>> When the range is a single page, do a page flush instead.
> 
>> +	start &= PAGE_MASK;
>> +	end = (end - 1) | ~PAGE_MASK;
>>   	if (!Hash) {
>> -		_tlbia();
>> +		if (end - start == PAGE_SIZE)
>> +			_tlbie(start);
>> +		else
>> +			_tlbia();
>>   		return;
>>   	}
> 
> For just one page, you get  end - start == 0  actually?
> 
> 

Oops, good catch.

Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.

Christophe