[PATCH] riscv: mm: fix regression due to update_mmu_cache change

[Conor Dooley]

On Mon, Jan 30, 2023 at 12:18:18AM +0300, Sergey Matyukevich wrote:
> From: Sergey Matyukevich <sergey.matyukevich at syntacore.com>
> 
> This is a partial revert of the commit 4bd1d80efb5a ("riscv: mm: notify
> remote harts about mmu cache updates"). Original commit included two
> loosely related changes serving the same purpose of fixing stale TLB
> entries causing user-space application crash:
> - introduce deferred per-ASID TLB flush for CPUs not running the task
> - switch to per-ASID TLB flush on all CPUs running the task in update_mmu_cache
> 
> According to report and discussion in [1], the second part caused a
> regression on Renesas RZ/Five SoC. For now restore the old behavior
> of the update_mmu_cache.
> 
> [1] https://lore.kernel.org/linux-riscv/20220829205219.283543-1-geomatsi@gmail.com/

If you respin for another reason, can you convert this into a "regular"
Link: trailer, so that it can be parsed with git's trailer functionality?
IOW, like so:
Link: https://lore.kernel.org/linux-riscv/20220829205219.283543-1-geomatsi@gmail.com/ [1]

Otherwise, glad to see you two get this sorted out, even if it is just a
revert.
Reviewed-by: Conor Dooley <conor.dooley at microchip.com>

Thanks,
Conor.

> Fixes: 4bd1d80efb5a ("riscv: mm: notify remote harts about mmu cache updates")
> Reported-by: "Lad, Prabhakar" <prabhakar.csengg at gmail.com>
> Signed-off-by: Sergey Matyukevich <sergey.matyukevich at syntacore.com>
> ---
>  arch/riscv/include/asm/pgtable.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 4eba9a98d0e3..4c3c130ee328 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -415,7 +415,7 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
>  	 * Relying on flush_tlb_fix_spurious_fault would suffice, but
>  	 * the extra traps reduce performance.  So, eagerly SFENCE.VMA.
>  	 */
> -	flush_tlb_page(vma, address);
> +	local_flush_tlb_page(address);
>  }
>  
>  #define __HAVE_ARCH_UPDATE_MMU_TLB
> -- 
> 2.39.0
> 
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