Re: [PATCH] ArmVirtPkg: restrict mapping attributes of normal memory to EFI_MEMORY_WB

[Laszlo Ersek <lersek@redhat.com>]

On 09/08/16 09:50, Ard Biesheuvel wrote:
> In general, on an ARM system, mapping normal memory as device memory may
> have unintended side effects, given that unaligned accesses or loads and
> stores with special semantics (e.g., load/store exclusive) may fault or
> may not work as expected.
> 
> Under KVM, the situation is even worse, since the host may not expect the
> guest to perform uncached accesses, and so writes to such an uncached
> region may get lost completely.
> 
> Since the only safe mapping type under KVM is EFI_MEMORY_WB, remove all
> other memory type attributes.
> 
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  ArmVirtPkg/HighMemDxe/HighMemDxe.c                                   | 3 +--
>  ArmVirtPkg/Library/ArmVirtMemoryInitPeiLib/ArmVirtMemoryInitPeiLib.c | 3 ---
>  2 files changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/ArmVirtPkg/HighMemDxe/HighMemDxe.c b/ArmVirtPkg/HighMemDxe/HighMemDxe.c
> index 7fd7e8e9a539..4d56e6236b54 100644
> --- a/ArmVirtPkg/HighMemDxe/HighMemDxe.c
> +++ b/ArmVirtPkg/HighMemDxe/HighMemDxe.c
> @@ -78,8 +78,7 @@ InitializeHighMemDxe (
>            Status = gDS->AddMemorySpace (
>                            EfiGcdMemoryTypeSystemMemory,
>                            CurBase, CurSize,
> -                          EFI_MEMORY_WB | EFI_MEMORY_WC |
> -                          EFI_MEMORY_WT | EFI_MEMORY_UC);
> +                          EFI_MEMORY_WB);
>  
>            if (EFI_ERROR (Status)) {
>              DEBUG ((EFI_D_ERROR,
> diff --git a/ArmVirtPkg/Library/ArmVirtMemoryInitPeiLib/ArmVirtMemoryInitPeiLib.c b/ArmVirtPkg/Library/ArmVirtMemoryInitPeiLib/ArmVirtMemoryInitPeiLib.c
> index 251e5314e61d..6f3e54b7afcb 100644
> --- a/ArmVirtPkg/Library/ArmVirtMemoryInitPeiLib/ArmVirtMemoryInitPeiLib.c
> +++ b/ArmVirtPkg/Library/ArmVirtMemoryInitPeiLib/ArmVirtMemoryInitPeiLib.c
> @@ -68,9 +68,6 @@ MemoryPeim (
>    ResourceAttributes = (
>        EFI_RESOURCE_ATTRIBUTE_PRESENT |
>        EFI_RESOURCE_ATTRIBUTE_INITIALIZED |
> -      EFI_RESOURCE_ATTRIBUTE_UNCACHEABLE |
> -      EFI_RESOURCE_ATTRIBUTE_WRITE_COMBINEABLE |
> -      EFI_RESOURCE_ATTRIBUTE_WRITE_THROUGH_CACHEABLE |
>        EFI_RESOURCE_ATTRIBUTE_WRITE_BACK_CACHEABLE |
>        EFI_RESOURCE_ATTRIBUTE_TESTED
>    );
> 

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Did you encounter any specific problem with these?

Thanks
Laszlo