linux-kernel - Re: [PATCH 2/2] arm64: dts: qcom: agatti: Address Gunyah memory alignment needs

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Message-ID: <aWDTdYYVkFjfw4-C@sumit-xelite>
Date: Fri, 9 Jan 2026 15:37:49 +0530
From: Sumit Garg <sumit.garg@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>, linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org, konradybcio@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, akhilpo@....qualcomm.com,
	vikash.garodia@....qualcomm.com, dikshita.agarwal@....qualcomm.com,
	robin.clark@....qualcomm.com, lumag@...nel.org,
	linux-kernel@...r.kernel.org,
	Sumit Garg <sumit.garg@....qualcomm.com>
Subject: Re: [PATCH 2/2] arm64: dts: qcom: agatti: Address Gunyah memory
 alignment needs

On Thu, Jan 08, 2026 at 01:43:30PM +0100, Konrad Dybcio wrote:
> On 1/8/26 11:50 AM, Sumit Garg wrote:
> > On Wed, Jan 07, 2026 at 12:29:02PM +0100, Konrad Dybcio wrote:
> >> On 1/5/26 6:46 AM, Sumit Garg wrote:
> >>> On Sat, Jan 03, 2026 at 09:49:04AM -0600, Bjorn Andersson wrote:
> >>>> On Mon, Dec 29, 2025 at 12:42:58PM +0530, Sumit Garg wrote:
> >>>>> From: Sumit Garg <sumit.garg@....qualcomm.com>
> >>>>>
> >>>>> Gunyah hypervisor requires it's memory start address to be 2MB aligned.
> >>>>> So the address map for Agatti is updated to incorporate that requirement.
> >>>>> This should be a backwards compatible DT change which should work with
> >>>>> legacy QHEE based firmware stack too.
> >>>>>
> >>>>
> >>>> How come this isn't conveyed to the operating system using the UEFI
> >>>> memory map?
> >>>>
> >>>
> >>> I agree that with EFI boot, the information is getting conveyed via EFI
> >>> memory map. But there will be non-EFI boot scenarios as well in case of
> >>> U-Boot. And moreover I suppose we need to keep the reserved memory
> >>> ranges in DT updated to reflect the actual memory map.
> >>
> >> Can U-Boot not do the same by altering /reserved-memory or /memory/reg?
> > 
> > I suppose you are referring to DT fixups here, we generally try to keep
> > them to a minimum required in U-Boot.
> > 
> > BTW, don't we want to keep reserved memory ranges updated in DT? Or we plan
> > to drop them altogether?
> 
> Generally I believe they're only a necessary evil..
> 
> Since Gunyah-on-Agatti doesn't seem to have been released yet, it would
> seem like a sane idea to fix the issue in the firmware. If it was, well..
> 
> On UEFI-enabled targets, we can largely rely on the reservations coming
> from there, only adding some carveouts for e.g. PIL regions and SMEM (not
> because they're not resereved, but because we need a pointer to them)
>

Fair enough, I don't see an immediate need for this from UEFI boot
perspective. Let me drop this patch then.

TBH, I am also not a fan of putting the memory regions configuration in
DT which can change based on evolving requirments.

-Sumit