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Re: [PATCH] xen/dt: Skip non-RAM reserved-memory regions in make_memory_node()
- To: Kuan-Wei Chiu <visitorckw@xxxxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Mon, 9 Nov 2026 08:34:49 +0100
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- Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxx>, <sstabellini@xxxxxxxxxx>, <julien@xxxxxxx>, <bertrand.marquis@xxxxxxx>, <marscheng@xxxxxxxxxx>, <jserv@xxxxxxxxxxxxxxxx>, <eleanor15x@xxxxxxxxx>
- Delivery-date: Mon, 09 Nov 2026 07:35:14 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 05-Nov-26 17:48, Kuan-Wei Chiu wrote:
> Hi Michal,
>
> On Mon, Nov 02, 2026 at 02:02:20PM +0100, Orzel, Michal wrote:
>>
>>
>> On 28-Oct-26 22:17, Kuan-Wei Chiu wrote:
>>> Xen creates a second /memory node for Dom0 from
>>> bootinfo_get_reserved_mem() without checking whether those regions
>>> belong to host RAM. However, /reserved-memory can also describe
>>> on-chip SRAM or firmware regions outside system RAM. Listing them in a
>>> /memory node causes Dom0 to register non-RAM addresses as system RAM,
>>> conflicting with device MMIO mappings.
>> It's worth adding a reference to Linux binding for nvmem-rmem as an example
>> (the
>> only one so far?) of /reserved-memory describing non RAM. Please also mention
>> Linux comment at early_init_dt_reserve_memory().
>
> Ack.
>
>>
>>>
>>> Skip reserved-memory banks outside the host RAM banks reported by
>>> bootinfo_get_mem() in make_memory_node().
>> Have you considered EFI boot? There we don't use /memory and
>> bootinfo_get_mem()
>> contains usable memory. IOW I think it does not contain reserved memory. In
>> such
>> scenario, we would skip the reserved regions because they are not described
>> in
>> memory membank. So it would be a regression in behavior.
>>
>
> I'm not quite familiar with EFI, so I indeed didn't consider the EFI
> boot scenario in the first place. I think I should skip the
> is_in_host_ram() check when efi_enabled(EFI_BOOT)?'
Yes, please do so.
~Michal
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