Re: [PATCH] parisc: Unconditionally flush tlb entry in tmpalias functions

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On 5/14/22 01:38, Helge Deller wrote:
> Drop the ALTERNATIVE() instructions in the tmpalias functions for the
> 32-bit kernel.
> Functions which use the tmpalias mappings to flush/copy/invalidate
> congruently mapped memory need to always flush the TLB entry prior
> accessing the newly-to-be mapped memory areas. This is independed if
> it's a SMP kernel or not.  Otherwise the new memory mappings (stored in
> r28 and possibly r23) won't get loaded into the TLB.
>
> Signed-off-by: Helge Deller <deller@xxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

This patch is contra-productive.
The ALTERNATIVE() replacement will only trigger on PA20 CPUs, in
which case the pdtlb gets replaced by pdtlb,l - which is good because
we use the tmpalias mapping only on the local currently CPU.

Helge

> diff --git a/arch/parisc/kernel/pacache.S b/arch/parisc/kernel/pacache.S
> index b4c3f01e2399..1cc55e668fe0 100644
> --- a/arch/parisc/kernel/pacache.S
> +++ b/arch/parisc/kernel/pacache.S
> @@ -565,10 +565,8 @@ ENTRY_CFI(copy_user_page_asm)
>  	pdtlb,l		%r0(%r28)
>  	pdtlb,l		%r0(%r29)
>  #else
> -0:	pdtlb		%r0(%r28)
> -1:	pdtlb		%r0(%r29)
> -	ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
> -	ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SMP, INSN_PxTLB)
> +	pdtlb		%r0(%r28)
> +	pdtlb		%r0(%r29)
>  #endif
>
>  #ifdef CONFIG_64BIT
> @@ -705,8 +703,7 @@ ENTRY_CFI(clear_user_page_asm)
>  #ifdef CONFIG_PA20
>  	pdtlb,l		%r0(%r28)
>  #else
> -0:	pdtlb		%r0(%r28)
> -	ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
> +	pdtlb		%r0(%r28)
>  #endif
>
>  #ifdef CONFIG_64BIT
> @@ -781,8 +778,7 @@ ENTRY_CFI(flush_dcache_page_asm)
>  #ifdef CONFIG_PA20
>  	pdtlb,l		%r0(%r28)
>  #else
> -0:	pdtlb		%r0(%r28)
> -	ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
> +	pdtlb		%r0(%r28)
>  #endif
>
>  88:	ldil		L%dcache_stride, %r1
> @@ -840,8 +836,7 @@ ENTRY_CFI(purge_dcache_page_asm)
>  #ifdef CONFIG_PA20
>  	pdtlb,l		%r0(%r28)
>  #else
> -0:	pdtlb		%r0(%r28)
> -	ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
> +	pdtlb		%r0(%r28)
>  #endif
>
>  88:	ldil		L%dcache_stride, %r1
> @@ -904,10 +899,8 @@ ENTRY_CFI(flush_icache_page_asm)
>  1:	pitlb,l         %r0(%sr4,%r28)
>  	ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SPLIT_TLB, INSN_NOP)
>  #else
> -0:	pdtlb		%r0(%r28)
> +	pdtlb		%r0(%r28)
>  1:	pitlb           %r0(%sr4,%r28)
> -	ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
> -	ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SMP, INSN_PxTLB)
>  	ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SPLIT_TLB, INSN_NOP)
>  #endif
>





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