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Subject: Re: [PATCH v2 4/4] OvmfPkg/PciHotPlugInitDxe: reserve more mmio space
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: devel@edk2.groups.io, Jordan Justen <jordan.l.justen@intel.com>,
 Pawel Polawski <ppolawsk@redhat.com>, Jiewen Yao <jiewen.yao@intel.com>,
 Oliver Steffen <osteffen@redhat.com>,
 Ard Biesheuvel <ardb+tianocore@kernel.org>
References: <20221004134728.55499-1-kraxel@redhat.com>
 <20221004134728.55499-5-kraxel@redhat.com>
 <6e33ffa4-4f06-c993-6ceb-474805e28cac@redhat.com>
 <20221005050156.y5vcmelhtnbwgcbt@sirius.home.kraxel.org>
From: "Laszlo Ersek" <lersek@redhat.com>
Message-ID: <2af33afb-89b9-38e6-8343-7b0981729058@redhat.com>
Date: Thu, 6 Oct 2022 10:50:03 +0200
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On 10/05/22 07:01, Gerd Hoffmann wrote:
> On Tue, Oct 04, 2022 at 05:57:46PM +0200, Laszlo Ersek wrote:
>> On 10/04/22 15:47, Gerd Hoffmann wrote:
>>> In case the 64-bit pci mmio window is larger than the default size
>>> of 32G be generous and hand out larger chunks of address space for
>>> prefetchable mmio bridge windows.
> 
>>> +      SetMmioPadding (
>>> +        --FirstResource,
>>> +        TRUE,
>>> +        FALSE,
>>> +        (UINTN)HighBitSetRoundUp64 (RShiftU64 (Pci64Size, 8))
>>> +        );
> 
>> Looks good to me, thanks; I'm just missing the rationale on the
>> RShiftU64() call. Please elaborate.
> 
> Cover letter explains this a bit.  The idea is to scale things up with
> the available address space.  Patch #3 does that for the 64-bit pci mmio
> window.  This patch does the same for the bridge windows, leveraging the
> patch #3 calculations by looking at PcdPciMmio64Size.  The shift by 8
> assigns 1/256 of the total mmio window size to each bridge.
> 
> The '8' is just pulled out of thin air.  Looks reasonable to me, in case
> it turns out it is not we can adjust that in the future.

OK, starting with a 64GB aperture size, 256MB will be reserved per port
/ bridge.

For this patch:

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Laszlo