Re: [Xen-devel] [PATCH v4 2/3] xen/efi: optionally call SetVirtualAddressMap()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 24.10.2019 05:45, Marek Marczykowski-Górecki wrote:
> Some UEFI implementations are not happy about lack of
> SetVirtualAddressMap() call. Likely abuse the address map change
> notification to do things beyond the necessary ConvertPointer() calls.
> Specifically, wihtout the SetVirtualAddressMap() call, some access
> EfiBootServices{Code,Data}, or even totally unmapped areas. Example
> crash of GetVariable() call on Thinkpad W540:
> 
>     Xen call trace:
>        [<0000000000000080>] 0000000000000080
>        [<8c2b0398e0000daa>] 8c2b0398e0000daa
> 
>     Pagetable walk from ffffffff858483a1:
>        L4[0x1ff] = 0000000000000000 ffffffffffffffff
> 
>     ****************************************
>     Panic on CPU 0:
>     FATAL PAGE FAULT
>     [error_code=0002]
>     Faulting linear address: ffffffff858483a1
>     ****************************************
> 
> Fix this by calling SetVirtualAddressMap() runtime service, giving it
> 1:1 map for areas marked as needed during runtime. The address space in
> which EFI runtime services are called is unchanged, but UEFI view of it
> may be.
> Since it's fairly late in Xen 4.13 development cycle, disable it
> by default and hide behind EXPERT.
> 
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

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