Re: [PATCH v2 2/3] riscv: mm: Apply Svinval in update_mmu_cache()

[Marek Szyprowski]

On 15.07.2026 20:22, Klara Modin wrote:
> On 2026-07-15 21:20:08 +0800, Xu Lu wrote:
>> Use Svinval in update_mmu_cache_range() when the extension is available.
>>
>> Signed-off-by: Xu Lu <luxu.kernel@xxxxxxxxxxxxx>
> This version works fine for me.

Lucky You! Here BPiF3 gets frozen once userspace has started.


> Thanks,
> Tested-by: Klara Modin <klarasmodin@xxxxxxxxx>
>
>> ---
>>  arch/riscv/include/asm/pgtable.h  |  8 ++++++++
>>  arch/riscv/include/asm/tlbflush.h | 18 ++++++++++++++++++
>>  arch/riscv/mm/tlbflush.c          | 18 ------------------
>>  3 files changed, 26 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
>> index 9926556099ae..823805cc465a 100644
>> --- a/arch/riscv/include/asm/pgtable.h
>> +++ b/arch/riscv/include/asm/pgtable.h
>> @@ -578,6 +578,14 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf,
>>  	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SVVPTC))
>>  		return;
>>  
>> +	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SVINVAL)) {
>> +		local_sfence_w_inval();
>> +		while (nr--)
>> +			local_sinval_vma(address + nr * PAGE_SIZE, asid);

'asid' is not initialized here. The following fixup is needed:

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 3c17ad0786ab..e283649e1dee 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -570,32 +570,32 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf,
        /*
         * Svvptc guarantees that the new valid pte will be visible within
         * a bounded timeframe, so when the uarch does not cache invalid
         * entries, we don't have to do anything.
         */
        if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SVVPTC))
                return;

+       asid = get_mm_asid(vma->vm_mm);
        if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SVINVAL)) {
                local_sfence_w_inval();
                while (nr--)
                        local_sinval_vma(address + nr * PAGE_SIZE, asid);
                local_sfence_inval_ir();
                return;
        }

        /*
         * The kernel assumes that TLBs don't cache invalid entries, but
         * in RISC-V, SFENCE.VMA specifies an ordering constraint, not a
         * cache flush; it is necessary even after writing invalid entries.
         * Relying on flush_tlb_fix_spurious_fault would suffice, but
         * the extra traps reduce performance.  So, eagerly SFENCE.VMA.
         */
-       asid = get_mm_asid(vma->vm_mm);
        while (nr--)
                local_flush_tlb_page_asid(address + nr * PAGE_SIZE, asid);
 }

 #define update_mmu_cache(vma, addr, ptep) \
        update_mmu_cache_range(NULL, vma, addr, ptep, 1)

 #define update_mmu_tlb_range(vma, addr, ptep, nr) \



>> +		local_sfence_inval_ir();
>> +		return;
>> +	}
>> +
>>  	/*
>>  	 * The kernel assumes that TLBs don't cache invalid entries, but
>>  	 * in RISC-V, SFENCE.VMA specifies an ordering constraint, not a
>> diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
>> index 7c2cd5cc92d3..9636d07fe9ee 100644
>> --- a/arch/riscv/include/asm/tlbflush.h
>> +++ b/arch/riscv/include/asm/tlbflush.h
>> @@ -20,6 +20,24 @@ static inline unsigned long get_mm_asid(struct mm_struct *mm)
>>  	return mm ? cntx2asid(atomic_long_read(&mm->context.id)) : FLUSH_TLB_NO_ASID;
>>  }
>>  
>> +static inline void local_sfence_inval_ir(void)
>> +{
>> +	asm volatile(SFENCE_INVAL_IR() ::: "memory");
>> +}
>> +
>> +static inline void local_sfence_w_inval(void)
>> +{
>> +	asm volatile(SFENCE_W_INVAL() ::: "memory");
>> +}
>> +
>> +static inline void local_sinval_vma(unsigned long vma, unsigned long asid)
>> +{
>> +	if (asid != FLUSH_TLB_NO_ASID)
>> +		asm volatile(SINVAL_VMA(%0, %1) : : "r" (vma), "r" (asid) : "memory");
>> +	else
>> +		asm volatile(SINVAL_VMA(%0, zero) : : "r" (vma) : "memory");
>> +}
>> +
>>  static inline void local_flush_tlb_all(void)
>>  {
>>  	__asm__ __volatile__ ("sfence.vma" : : : "memory");
>> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
>> index 73c226f719c7..962db300a166 100644
>> --- a/arch/riscv/mm/tlbflush.c
>> +++ b/arch/riscv/mm/tlbflush.c
>> @@ -11,24 +11,6 @@
>>  
>>  #define has_svinval()	riscv_has_extension_unlikely(RISCV_ISA_EXT_SVINVAL)
>>  
>> -static inline void local_sfence_inval_ir(void)
>> -{
>> -	asm volatile(SFENCE_INVAL_IR() ::: "memory");
>> -}
>> -
>> -static inline void local_sfence_w_inval(void)
>> -{
>> -	asm volatile(SFENCE_W_INVAL() ::: "memory");
>> -}
>> -
>> -static inline void local_sinval_vma(unsigned long vma, unsigned long asid)
>> -{
>> -	if (asid != FLUSH_TLB_NO_ASID)
>> -		asm volatile(SINVAL_VMA(%0, %1) : : "r" (vma), "r" (asid) : "memory");
>> -	else
>> -		asm volatile(SINVAL_VMA(%0, zero) : : "r" (vma) : "memory");
>> -}
>> -
>>  /*
>>   * Flush entire TLB if number of entries to be flushed is greater
>>   * than the threshold below.
>> -- 
>> 2.39.5
>>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland