Re: [PATCH 1/4] parisc: disable preemption during local tlb flush

[Helge Deller <deller@gmx.de>]

On 10/8/21 23:35, Sven Schnelle wrote:
> Sven Schnelle <svens@stackframe.org> writes:
>
>> flush_cache_mm() fetches %sr3 via mtsp(3). If it matches mm->context,
>> it flushes caches and the TLB. However, the TLB is cpu-local, so if the
>> code gets preempted shortly after the mtsp(), and later resumed on another
>> CPU, the wrong TLB is flushed.
>>
>> Signed-off-by: Sven Schnelle <svens@stackframe.org>
>> ---
>>  arch/parisc/kernel/cache.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
>> index 39e02227e231..90656c49bc07 100644
>> --- a/arch/parisc/kernel/cache.c
>> +++ b/arch/parisc/kernel/cache.c
>> @@ -558,6 +558,7 @@ void flush_cache_mm(struct mm_struct *mm)
>>  		return;
>>  	}
>>
>> +	preempt_disable();
>>  	if (mm->context == mfsp(3)) {
>>  		for (vma = mm->mmap; vma; vma = vma->vm_next) {
>>  			flush_user_dcache_range_asm(vma->vm_start, vma->vm_end);
>> @@ -565,8 +566,10 @@ void flush_cache_mm(struct mm_struct *mm)
>>  				flush_user_icache_range_asm(vma->vm_start, vma->vm_end);
>>  			flush_tlb_range(vma, vma->vm_start, vma->vm_end);
>>  		}
>> +		preempt_enable();
>>  		return;
>>  	}
>> +	preempt_enable();
>>
>>  	pgd = mm->pgd;
>>  	for (vma = mm->mmap; vma; vma = vma->vm_next) {
>
> I noticed that flush_cache_range() has the same problem. Helge, let me
> know whether i should send a v2 with an additional patch, or a single
> follow up patch. Both functions also look very similar, so i think
> best would be to combine the code of these two functions.

I'm fine with either option.

Thanks for your patches!
Helge