linux-kernel - Re: [PATCH 1/4] riscv: tlb: fix __p*d_free

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Date: Wed, 10 Jan 2024 06:52:33 -0800 (PST)
From: Palmer Dabbelt <palmer@...belt.com>
To: alex@...ti.fr
CC: jszhang@...nel.org, Paul Walmsley <paul.walmsley@...ive.com>,
  aou@...s.berkeley.edu, Will Deacon <will@...nel.org>, aneesh.kumar@...ux.ibm.com,
  akpm@...ux-foundation.org, npiggin@...il.com, peterz@...radead.org,
  Conor Dooley <conor.dooley@...rochip.com>, linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
  linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject:     Re: [PATCH 1/4] riscv: tlb: fix __p*d_free_tlb()

On Thu, 04 Jan 2024 02:55:40 PST (-0800), alex@...ti.fr wrote:
> On 19/12/2023 18:50, Jisheng Zhang wrote:
>> If non-leaf PTEs I.E pmd, pud or p4d is modified, a sfence.vma is
>> a must for safe, imagine if an implementation caches the non-leaf
>> translation in TLB, although I didn't meet this HW so far, but it's
>> possible in theory.
>
>
> And since this is a fix, it would be worth trying to add a Fixes tag
> here. Not easy I agree because it fixes several commits (I have
> 07037db5d479f,  e8a62cc26ddf5, d10efa21a9374 and c5e9b2c2ae822 if you
> implement tlb_flush() as I suggested).
>
> So I would add the latest commit as the Fixes commit (which would be
> c5e9b2c2ae822), and then I'd send a patch to stable for each commit with
> the right Fixes tag...@...or: let me know if you have a simpler idea or
> if this is wrong.

I just went with

Fixes: c5e9b2c2ae82 ("riscv: Improve tlb_flush()")
Cc: stable@...r.kernel.org

hopefully that's fine.  It's still getting tested, it's batched up with 
some other stuff and I managed to find a bad merge so it might take a 
bit...

>
> Thanks,
>
> Alex
>
>
>> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
>> ---
>>   arch/riscv/include/asm/pgalloc.h | 20 +++++++++++++++++---
>>   1 file changed, 17 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
>> index d169a4f41a2e..a12fb83fa1f5 100644
>> --- a/arch/riscv/include/asm/pgalloc.h
>> +++ b/arch/riscv/include/asm/pgalloc.h
>> @@ -95,7 +95,13 @@ static inline void pud_free(struct mm_struct *mm, pud_t *pud)
>>   		__pud_free(mm, pud);
>>   }
>>
>> -#define __pud_free_tlb(tlb, pud, addr)  pud_free((tlb)->mm, pud)
>> +#define __pud_free_tlb(tlb, pud, addr)					\
>> +do {									\
>> +	if (pgtable_l4_enabled) {					\
>> +		pagetable_pud_dtor(virt_to_ptdesc(pud));		\
>> +		tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pud));	\
>> +	}								\
>> +} while (0)
>>
>>   #define p4d_alloc_one p4d_alloc_one
>>   static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr)
>> @@ -124,7 +130,11 @@ static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
>>   		__p4d_free(mm, p4d);
>>   }
>>
>> -#define __p4d_free_tlb(tlb, p4d, addr)  p4d_free((tlb)->mm, p4d)
>> +#define __p4d_free_tlb(tlb, p4d, addr)					\
>> +do {									\
>> +	if (pgtable_l5_enabled)						\
>> +		tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(p4d));	\
>> +} while (0)
>>   #endif /* __PAGETABLE_PMD_FOLDED */
>>
>>   static inline void sync_kernel_mappings(pgd_t *pgd)
>> @@ -149,7 +159,11 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm)
>>
>>   #ifndef __PAGETABLE_PMD_FOLDED
>>
>> -#define __pmd_free_tlb(tlb, pmd, addr)  pmd_free((tlb)->mm, pmd)
>> +#define __pmd_free_tlb(tlb, pmd, addr)				\
>> +do {								\
>> +	pagetable_pmd_dtor(virt_to_ptdesc(pmd));		\
>> +	tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pmd));	\
>> +} while (0)
>>
>>   #endif /* __PAGETABLE_PMD_FOLDED */
>>