Re: [PATCH v2 2/3] OvmfPkg/PlatformInitLib: move mmconfig to 0xe0000000

["Anthony PERARD" <anthony.perard@citrix.com>]

On Tue, Mar 07, 2023 at 07:54:53AM +0100, Gerd Hoffmann wrote:
> Also swap the ordering of 32bit PCI MMIO window on q35, i.e. use the
> room between end of low memory and the start of the mmconfig bar.
> 
> With a typical configuration on modern qemu with gigabyte-aligned memory
> the MMIO window start at 0x8000000, sized 1532 MB.  In case there is
> memory present above 0x80000000 the window will start at 0xc0000000
> instead, with 512 MB size.
> 
> This depends on qemu commit 4a4418369d6d ("q35: fix mmconfig and
> PCI0._CRS"), so it raises the bar for the lowest supported version
> to qemu 4.1 (released Aug 2019).

Maybe this new version requirement should be noted in OvmfPkg/README,
but I'm not sure were as it affect only machine started with Q35.



> diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc
> index c328987e8432..18144d9a6d94 100644
> --- a/OvmfPkg/OvmfXen.dsc
> +++ b/OvmfPkg/OvmfXen.dsc
> @@ -434,7 +434,7 @@ [PcdsFixedAtBuild]
>    #
>    # On Q35 machine types that QEMU intends to support in the long term, QEMU
>    # never lets the RAM below 4 GB exceed 2816 MB.
> -  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xB0000000
> +  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xE0000000

Could you remove this change? OvmfXen doesn't use PlatformInitLib, and
we still have worked to do to be able to use Q35 in Xen guest.


I think the rest looks fine, so:
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

Thanks,

-- 
Anthony PERARD