Re: [Xen-devel] [PATCH MM-PART2 RESEND v2 19/19] xen/arm: Pair call to set_fixmap with call to clear_fixmap in copy_from_paddr

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 14 May 2019, Julien Grall wrote:
> At the moment, set_fixmap may replace a valid entry without following
> the break-before-make sequence. This may result to TLB conflict abort.
> 
> Rather than dealing with Break-Before-Make in set_fixmap, every call to
> set_fixmap is paired with a call to clear_fixmap.

It is not every call to set_fixmap: it is every call to
set_fixmap(FIXMAP_MISC, ...

Please clarify, then you can add

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
>
> ---
>     Changes in v2:
>         - Add Andrii's reviewed-by
> ---
>  xen/arch/arm/kernel.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/kernel.c b/xen/arch/arm/kernel.c
> index e3ffdb2fa1..389bef2afa 100644
> --- a/xen/arch/arm/kernel.c
> +++ b/xen/arch/arm/kernel.c
> @@ -58,13 +58,12 @@ void __init copy_from_paddr(void *dst, paddr_t paddr, 
> unsigned long len)
>          set_fixmap(FIXMAP_MISC, maddr_to_mfn(paddr), PAGE_HYPERVISOR_WC);
>          memcpy(dst, src + s, l);
>          clean_dcache_va_range(dst, l);
> +        clear_fixmap(FIXMAP_MISC);
>  
>          paddr += l;
>          dst += l;
>          len -= l;
>      }
> -
> -    clear_fixmap(FIXMAP_MISC);
>  }
>  
>  static void __init place_modules(struct kernel_info *info,
> -- 
> 2.11.0
> 

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