Re: [PATCH v3 2/2] ArmPkg/ArmMmuLib AARCH64: invalidate page tables before populating them

["Leif Lindholm" <leif@nuviainc.com>]

On Fri, Mar 06, 2020 at 17:12:46 +0100, Ard Biesheuvel wrote:
> As it turns out, ARMv8 also permits accesses made with the MMU and
> caches off to hit in the caches, so to ensure that any modifications
> we make before enabling the MMU are visible afterwards as well, we
> should invalidate page tables right after allocation like we do now on
> ARM, if the MMU is still disabled at that point.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Urgh.
Reviewed-by: Leif Lindholm <leif@nuviainc.com>

> ---
>  ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> index e36594fea3ad..10ca8bac6a3f 100644
> --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> @@ -217,6 +217,14 @@ UpdateRegionMappingRec (
>            return EFI_OUT_OF_RESOURCES;
>          }
>  
> +        if (!ArmMmuEnabled ()) {
> +          //
> +          // Make sure we are not inadvertently hitting in the caches
> +          // when populating the page tables.
> +          //
> +          InvalidateDataCacheRange (TranslationTable, EFI_PAGE_SIZE);
> +        }
> +
>          if ((*Entry & TT_TYPE_MASK) == TT_TYPE_BLOCK_ENTRY) {
>            //
>            // We are splitting an existing block entry, so we have to populate
> @@ -581,6 +589,12 @@ ArmConfigureMmu (
>      *TranslationTableSize = RootTableEntryCount * sizeof(UINT64);
>    }
>  
> +  //
> +  // Make sure we are not inadvertently hitting in the caches
> +  // when populating the page tables.
> +  //
> +  InvalidateDataCacheRange (TranslationTable,
> +    RootTableEntryCount * sizeof(UINT64));
>    ZeroMem (TranslationTable, RootTableEntryCount * sizeof(UINT64));
>  
>    TranslationTableAttribute = TT_ATTR_INDX_INVALID;
> -- 
> 2.17.1
>