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Re: [PATCH-4.16 v2] xen/efi: Fix Grub2 boot on arm64
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 9 Nov 2021 12:00:58 +0100
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- Cc: Bertrand Marquis <bertrand.marquis@xxxxxxx>, wei.chen@xxxxxxx, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Luca Fancellu <luca.fancellu@xxxxxxx>
- Delivery-date: Tue, 09 Nov 2021 11:01:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 09.11.2021 03:11, Stefano Stabellini wrote:
> On Mon, 8 Nov 2021, Jan Beulich wrote:
>> On 05.11.2021 16:33, Stefano Stabellini wrote:
>>> My main concern is performance and resource utilization. With v3 of the
>>> patch get_parent_handle will get called for every module to be loaded.
>>> With dom0less, it could easily get called 10 times or more. Taking a
>>> look at get_parent_handle, the Xen side doesn't seem small and I have
>>> no idea how the EDK2 side looks. I am just worried that it would
>>> actually have an impact on boot times (also depending on the bootloader
>>> implementation).
>>
>> The biggest part of the function deals with determining the "residual" of
>> the file name. That part looks to be of no interest at all to
>> allocate_module_file() (whether that's actually correct I can't tell). I
>> don't see why this couldn't be made conditional (e.g. by passing in NULL
>> for "leaf").
>
> I understand the idea of passing NULL instead of "leaf", but I tried
> having a look and I can't tell what we would be able to skip in
> get_parent_handle.
My bad - I did overlook that dir_handle gets updated even past the
initial loop.
> Should we have a global variable to keep the dir_handle open during
> dom0less module loading?
If that's contained within Arm-specific code, I (obviously) don't mind.
Otherwise I remain to be convinced.
Jan
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