Re: [Xen-devel] [PATCH 10/18] xen/arm32: Use cpu_hwcaps to skip the check of pending serrors

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 13 Mar 2017, Wei Chen wrote:
> We have provided an option to administrator to determine how to
> handle the SErrors. In order to skip the check of pending SError,
> in conventional way, we have to read the option every time before
> we try to check the pending SError.
> 
> Currently, we haven't export the option to other source file. But,
> in the previous patch, we had set "SKIP_CHECK_PENDING_VSERROR" to
> cpu_hwcaps when the option doesn't need to check the SErrors. So we
> can use checking cpu_hwcaps to replace checking the option directly.
> 
> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> This is a temporary solution, this would have to be dropped as soon
> as ARM32 gain support of alternative patching to avoid potential misusage.
> The alternative patching support patches for ARM32 are still in review
> stage.
> ---
>  xen/arch/arm/arm32/entry.S | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
> index 2187226..79929ca 100644
> --- a/xen/arch/arm/arm32/entry.S
> +++ b/xen/arch/arm/arm32/entry.S
> @@ -1,5 +1,6 @@
>  #include <asm/asm_defns.h>
>  #include <asm/regs.h>
> +#include <asm/cpufeature.h>
>  #include <public/xen.h>
>  
>  #define SAVE_ONE_BANKED(reg)    mrs r11, reg; str r11, [sp, #UREGS_##reg]
> @@ -11,6 +12,21 @@
>  #define RESTORE_BANKED(mode) \
>          RESTORE_ONE_BANKED(SP_##mode) ; RESTORE_ONE_BANKED(LR_##mode) ; 
> RESTORE_ONE_BANKED(SPSR_##mode)
>  
> +/*
> + * If the SKIP_CHECK_PENDING_VSERROR has been set in the cpu feature,
> + * the checking of pending SErrors will be skipped.
> + *
> + * As it is a temporary solution, we are assuming that
> + * SKIP_CHECK_PENDING_VSERROR will always be in the first word for
> + * cpu_hwcaps. This would have to be dropped as soon as ARM32 gain
> + * support of alternative.
> + */
> +#define SKIP_VSERROR_CHECK                      \
> +        ldr r1, =cpu_hwcaps;                    \
> +        ldr r1, [r1];                           \
> +        tst r1, #SKIP_CHECK_PENDING_VSERROR;    \
> +        moveq pc, lr
> +
>  #define SAVE_ALL                                                        \
>          sub sp, #(UREGS_SP_usr - UREGS_sp); /* SP, LR, SPSR, PC */      \
>          push {r0-r12}; /* Save R0-R12 */                                \
> @@ -44,6 +60,9 @@ save_guest_regs:
>          SAVE_BANKED(fiq)
>          SAVE_ONE_BANKED(R8_fiq); SAVE_ONE_BANKED(R9_fiq); 
> SAVE_ONE_BANKED(R10_fiq)
>          SAVE_ONE_BANKED(R11_fiq); SAVE_ONE_BANKED(R12_fiq);
> +
> +        SKIP_VSERROR_CHECK
> +
>          /*
>           * Start to check pending virtual abort in the gap of Guest -> HYP
>           * world switch.
> -- 
> 2.7.4
> 
> 
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> Xen-devel@xxxxxxxxxxxxx
> https://lists.xen.org/xen-devel
> 

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