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Re: [PATCH for-4.22 v2.5] xen/arm: gic: defer host LPI allocation until after ITS init
- To: Mykola Kvach <mykola_kvach@xxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Fri, 19 Jun 2026 08:09:14 +0200
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, "Volodymyr Babchuk" <Volodymyr_Babchuk@xxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, Luca Fancellu <luca.fancellu@xxxxxxx>, "Mykola Kvach" <xakep.amatop@xxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
- Delivery-date: Fri, 19 Jun 2026 06:09:40 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 19-Jun-26 07:45, Mykola Kvach wrote:
> gicv3_lpi_init_host_lpis() allocates host LPI state, including the
> host LPI lookup table, CPU notifier state and the boot CPU pending table.
> Those allocations use gicv3_its_get_memflags().
>
> ITS quirks are discovered by gicv3_its_init(), so allocating host LPI
> state from gicv3_dist_init() can happen before the memory restrictions
> required by the ITS are known. On affected systems this can leave
> Redistributor LPI state allocated and programmed with the default memory
> policy.
>
> Move host LPI initialization after gicv3_its_init(), and only run it when
> a host ITS was found. The old call ignored the return value. Now that the
> call is made from gicv3_init(), check it and panic on failure because
> Redistributor LPI initialization relies on that state being available.
>
> This also narrows the condition for host LPI initialization from
> "GICD advertises LPIs" to "a host ITS was discovered". This is
> intentional: Xen currently has no supported LPI path without a host ITS,
> and gicv3_lpi_init_rdist() already rejects that case with -ENODEV.
> Therefore, on systems where GICD_TYPE_LPIS is set but no host ITS is
> present, skipping gicv3_lpi_init_host_lpis() only avoids allocating host
> LPI state that cannot be used by a supported Xen LPI path.
>
> Fixes: dcb6cb263689 ("ARM: GICv3 ITS: introduce host LPI array")
> Fixes: 751ec850ec1d ("ARM: ITS: implement quirks and add support for Renesas
> Gen4 ITS")
> Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
~Michal
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