[edk2-devel] mmio mappings for runtime service
Yao, Jiewen
jiewen.yao at intel.com
Mon Aug 30 13:01:33 UTC 2021
The BIOS driver must set EFI_RUNTIME_MEMORY attribute for the EfiGcdMemoryTypeMemoryMappedIo region with GCD service gDS->SetMemorySpaceAttributes().
Then DXE will report EfiMemoryMappedIO with EFI_RUNTIME_MEMORY attribute in UEFI memory map.
The OS will gBS->GetMemoryMap() and assign virtual address for the MMIO, and gRT->SetVirtualAddressMap() back to the BIOS.
Finally, the BIOS driver can gRT->ConvertPointer() the MMIO physical address to virtual address, then access it at runtime.
Thank you
Yao Jiewen
> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Gerd
> Hoffmann
> Sent: Monday, August 30, 2021 6:24 PM
> To: devel at edk2.groups.io
> Subject: [edk2-devel] mmio mappings for runtime service
>
> Hi,
>
> What is the correct way to make sure runtime services can access
> mmio registers, i.e. that there is a mapping in the page tables
> for the mmio page needed?
>
> Is that the job of the firmware?
> Or should the OS calling the runtime service handle that?
> In case of the latter: How does the OS figure which pages are needed?
>
> thanks,
> Gerd
>
>
>
>
>
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