RE: [PATCH] OvmfPkg: reserve igd memory by E820

Hi,

> Where does the intel gop driver come from?  Extracted from host
> firmware?

https://projectacrn.github.io/latest/tutorials/gpu-passthru.html#enable-the-gvt-d-gop-driver

I don't know if it's possible to extract it from host firmware within
OS context easily. According to Intel you should ask your board
manufacturer. We're producing our own motherboards with an own
BIOS. So, I'm reusing the Intel GOP driver from our host BIOS.

> Ah, ok, didn't notice the subtile differences with the small letter at
> the end.  GVT-d + GVT-g is clear then.  What is GVT-s ?

https://01.org/sites/default/files/downloads/igvt-g/gvtflyer.pdf

I'm not familiar with GVT-s. I just know that it exists.

> Ideally the guest would allocate and initialize this all itself.
> That is hard for the GSM though when it requires an identity
> mapping.
>
> Having the guest check whenever the GSM register points to reserved
> memory and if so use it instead of allocating memory should work I
> think.

To allocate GSM, the guest has to detect the size of GSM. Detecting
the size is platform dependent. Writing a small EFI driver to
detect the GSM size and to allocate a proper memory region should
be easy.

https://github.com/torvalds/linux/blob/master/arch/x86/kernel/early-quirks.c#L353-L460

> Once we have the code for vgabios and PlatformGopPolicy we can roll them
> with the intelgop driver into a rom image with EfiRom.  Ideally also add
> opregion content to the rom somehow.

Sounds good. Does these EFI drivers have to be maintained outside of
EDKII?


Best regards
Corvin


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