Re: [Xen-devel] [PATCH v2 18/20] xen/arm32/livepatch: Add BPICALLIS to helper to invalidate all instruction caches

[Julien Grall <julien.grall@xxxxxxx>]

Hi Konrad,

On 25/08/16 14:37, Konrad Rzeszutek Wilk wrote:
> When we are flushing the cache we are most likley also want
> to flush the branch predictor too. Hence add this.
I think it makes more sense to fold this patch into #18 because 
ICIALLUIS may flush the branch predictor if the instruction cache is 
separate (see Table B4-35 in ARM DDI 0406C.c).
Therefore we need to be consistent and also flush the branch predictor 
for unified cache.
> Suggested-by: Julien Grall <julien.grall@xxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>
> ---
> Cc: Julien Grall <julien.grall@xxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
> v2: First submission
> ---
>  xen/arch/arm/livepatch.c         | 3 +++
>  xen/include/asm-arm/arm32/page.h | 5 ++++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/livepatch.c b/xen/arch/arm/livepatch.c
> index c290602..cdb8d65 100644
> --- a/xen/arch/arm/livepatch.c
> +++ b/xen/arch/arm/livepatch.c
> @@ -45,6 +45,9 @@ void arch_livepatch_revive(void)
>      /*
>       * Nuke the instruction cache. Data cache has been cleaned before in
>       * arch_livepatch_apply_jmp.
> +     *
> +     * Need to flush the branch predictor for ARMv7 as it may be
> +     * architecturally visible to the software (see B2.2.4 in ARM DDI 0406C.b).
I don't think this comment belongs to livepatch.c. It describes the 
behavior internal behavior of invalidate_icache.
>       */
>      invalidate_icache();
>
> diff --git a/xen/include/asm-arm/arm32/page.h b/xen/include/asm-arm/arm32/page.h
> index 26184ec..6caf596 100644
> --- a/xen/include/asm-arm/arm32/page.h
> +++ b/xen/include/asm-arm/arm32/page.h
> @@ -32,7 +32,10 @@ static inline void write_pte(lpae_t *p, lpae_t pte)
>  /* Invalidate all instruction caches in Inner Shareable domain to PoU */
>  static inline void invalidate_icache(void)
>  {
> -    asm volatile (CMD_CP32(ICIALLUIS));
> +    asm volatile (
> +        CMD_CP32(ICIALLUIS)     /* Flush I-cache. */
> +        CMD_CP32(BPIALLIS)      /* Flush branch predictor. */
> +        : : : "memory");
>  }
>
>  /*
Regards,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel