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RE: [PATCH 1/1] xen/efi: Config parsing: Free the same page count as allocated.
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Bernhard Kaindl <bernhard.kaindl@xxxxxxxxxx>
- Date: Wed, 22 Apr 2026 08:46:47 +0000
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- Cc: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>, Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
- Delivery-date: Wed, 22 Apr 2026 08:46:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHc0aotn+eeGsDBDUy6ubJIW0SdtbXqpN2AgAAZdoCAAAJOoA==
- Thread-topic: [PATCH 1/1] xen/efi: Config parsing: Free the same page count as allocated.
Jan Beulich wrote at 10:20:
> On 22.04.2026 08:48, Jan Beulich wrote:
>
> > As indicated above, I'm not convinced though that we really want to
> > alter file->size. I'd instead add 1 in the few instances of
> > "efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size))". Sadly the adding of 1
> > is conditional in read_section(), so maybe a "need_to_increment"
> > boolean wants adding next to the need_to_free one? Then a small helper
> > function may be warranted for those few instances of freeing cfg.addr.
>
> Actually, no separate flag looks to be needed. If for the cfg file we set
> ->need_to_free, we know we allocated the one extra byte.
No, also cfg->need_to_free is always set when AllocatePages was successful,
xen/common/efi/boot.c, read_file(), lines 862 to 867:
ret = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
PFN_UP(size + (file == &cfg)), &file->addr);
if ( EFI_ERROR(ret) )
goto fail;
file->need_to_free = true;
Given that, I think the EFI maintainers should state their preference on how
to free the allocated pages. It looks safest to add file->nr_allocated_pages.
Then we have a clean, dedicated value. I can update it in this way, but I'll
probably wait for the opinion of the EFI maintainers. It would be cleaner.
Bernhard
PS: I'm leaving this for the EFI maintainers for now, as I need to focus on
the review of the NUMA claims series.
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