Date: Wed, 24 Jan 2024 09:41:27 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Dennis Zhou <dennis@...nel.org>, yunhui cui <cuiyunhui@...edance.com>,
 Alexandre Ghiti <alexghiti@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Geert Uytterhoeven <geert@...ux-m68k.org>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [External] [PATCH] riscv: Fix wrong size passed to
 local_flush_tlb_range_asid()

On 24/01/2024 09:38, Alexandre Ghiti wrote:
> Hi Dennis, Yunhui,
>
> On 24/01/2024 09:19, Dennis Zhou wrote:
>> Hello,
>>
>> On Wed, Jan 24, 2024 at 10:44:12AM +0800, yunhui cui wrote:
>>> Hi Alexandre,
>>>
>>> On Tue, Jan 23, 2024 at 9:31 PM Alexandre Ghiti 
>>> <alexghiti@...osinc.com> wrote:
>>>> local_flush_tlb_range_asid() takes the size as argument, not the 
>>>> end of
>>>> the range to flush, so fix this by computing the size from the end and
>>>> the start of the range.
>>>>
>>>> Fixes: 7a92fc8b4d20 ("mm: Introduce flush_cache_vmap_early()")
>>>> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
>>>> ---
>>>>   arch/riscv/mm/tlbflush.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
>>>> index 8d12b26f5ac3..9619965f6501 100644
>>>> --- a/arch/riscv/mm/tlbflush.c
>>>> +++ b/arch/riscv/mm/tlbflush.c
>>>> @@ -68,7 +68,7 @@ static inline void 
>>>> local_flush_tlb_range_asid(unsigned long start,
>>>>
>>>>   void local_flush_tlb_kernel_range(unsigned long start, unsigned 
>>>> long end)
>>>>   {
>>>> -       local_flush_tlb_range_asid(start, end, PAGE_SIZE, 
>>>> FLUSH_TLB_NO_ASID);
>>>> +       local_flush_tlb_range_asid(start, end - start, PAGE_SIZE, 
>>>> FLUSH_TLB_NO_ASID);
>>>>   }
>> Well this was a miss during code review.. I'm going to take another look
>> tomorrow and then likely pull this into a fixes branch.
>>
>>> What makes me curious is that this patch has not been tested?
>>> BTW, It is best to keep the parameter order of all functions in
>>> tlbflush.c consistent: cpumask, start, size, stride, asid.
>>>
>> I can't speak to the riscv communities testing/regression suites, but
>> this would only be caught in a performance regression test.
>>
>> That being said, Alexandre, can you please lmk what level of testing
>> this has gone through?
>
>
> All my patches go through the same level of testing:
>
> * Build/boot an Ubuntu kernel with and without KASAN + a few simple 
> testsuites (libhugetlbfs, riscv kselftests and other)
> * Build/boot a simple rootfs on ~40 different rv64 configs
> * Build/boot a simple rootfs on ~30 different rv32 configs
>
> And I run LTP/full kselftests/perf testsuite on a weekly basis on 
> every rc. All this validation is done on qemu.
>
> The patch is functional, it "simply" flushes the whole TLB instead of 
> a few entries, so the only way to catch that would have been a 
> performance regression. But given it only runs on qemu, it would have 
> been hard to catch any performance regression since that involves the 
> TLB.
>
> @Yunhui: Please let me know how I should validate my patches better.


@Yunhui: And BTW, we lack reviewers, so feel free to help ;)


>
> Thanks,
>
> Alex
>
>
>> Thanks,
>> Dennis
>>
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