Re: [edk2-devel] [PATCH] OvmfPkg/XenPlatformPei: Relocate shared_info page mapping

[Jan Beulich <jbeulich@suse.com>]

On 29.06.2021 11:20, Laszlo Ersek wrote:
> On 06/28/21 15:23, Anthony PERARD via groups.io wrote:
>> From: Anthony PERARD <anthony.perard@citrix.com>
>>
>> Unfortunately, Xen isn't ready to deal with mapping at the top of the
>> physical address space, so we relocate the mapping after the LAPIC
>> location.
>>
>> See this thread about the issue with the mapping:
>> - https://lore.kernel.org/xen-devel/f8c4151a-6dac-d87c-ef46-eb35ada07bd9@suse.com/
>>
>> The PhysicalAddressIdentityMapping() call isn't going to do anything
>> anymore since everything under 4GB is already mapped, but there is no
>> need to remove the call.
>>
>> CC: Jan Beulich <JBeulich@suse.com>
>> CC: Andrew Cooper <andrew.cooper3@citrix.com>
>> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
>> ---
>>  OvmfPkg/XenPlatformPei/Xen.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/OvmfPkg/XenPlatformPei/Xen.c b/OvmfPkg/XenPlatformPei/Xen.c
>> index a4e82b356936..9c6641895970 100644
>> --- a/OvmfPkg/XenPlatformPei/Xen.c
>> +++ b/OvmfPkg/XenPlatformPei/Xen.c
>> @@ -569,7 +569,7 @@ CalibrateLapicTimer (
>>    EFI_STATUS            Status;
>>  
>>  
>> -  SharedInfo = (VOID*)((1ULL << mPhysMemAddressWidth) - EFI_PAGE_SIZE);
>> +  SharedInfo = (VOID*)((UINTN)PcdGet32 (PcdCpuLocalApicBaseAddress) + SIZE_1MB);
>>    Status = PhysicalAddressIdentityMapping ((EFI_PHYSICAL_ADDRESS)SharedInfo);
>>    if (EFI_ERROR (Status)) {
>>      DEBUG ((DEBUG_ERROR,
>>
> 
> Acked-by: Laszlo Ersek <lersek@redhat.com>
> 
> I guess I should merge this after Jan and/or Andrew ack it.

Well, I can informally ack that a move like this is needed, but I can't
really give an Acked-by on the change, as I know next to nothing about
ovmf, and hence I cannot, for example, tell whether the chosen new
location is okay to use there.

Jan