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

[Samuel Holland <samuel.holland@sifive.com>]

Hi Xu Lu,

On 2026-07-15 8:20 AM, Xu Lu wrote:
> Use Svinval in update_mmu_cache_range() when the extension is available.
> 
> Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
> ---
>  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);
> +		local_sfence_inval_ir();
> +		return;
> +	}
> +

This duplicates the logic in local_flush_tlb_range_threshold_asid(). If you
exported local_flush_tlb_range_mm(), you could use that here without rearranging
any of the other functions, and it also be able to reuse the threshold logic,
which is important on platforms that set local_flush_tlb_range_mm = 1 to always
do full-address-space flushes.

Regards,
Samuel

>  	/*
>  	 * 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.