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Re: [PATCH] xen/arm: alternative: Don't call vmap() within stop_machine_run()
- To: Julien Grall <julien@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 27 Apr 2022 08:42:26 +0200
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- Cc: Julien Grall <jgrall@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, David Vrabel <dvrabel@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 27 Apr 2022 06:42:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 26.04.2022 22:06, Julien Grall wrote:
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> Commit 88a037e2cfe1 "page_alloc: assert IRQs are enabled in heap
> alloc/free" extended the checks in the buddy allocator to catch
> any use of the helpers from context with interrupts disabled.
>
> Unfortunately, the rule is not followed in the alternative code and
> this will result to crash at boot with debug enabled:
>
> (XEN) Xen call trace:
> (XEN) [<0022a510>] alloc_xenheap_pages+0x120/0x150 (PC)
> (XEN) [<00000000>] 00000000 (LR)
> (XEN) [<002736ac>] arch/arm/mm.c#xen_pt_update+0x144/0x6e4
> (XEN) [<002740d4>] map_pages_to_xen+0x10/0x20
> (XEN) [<00236864>] __vmap+0x400/0x4a4
> (XEN) [<0026aee8>]
> arch/arm/alternative.c#__apply_alternatives_multi_stop+0x144/0x1ec
> (XEN) [<0022fe40>] stop_machine_run+0x23c/0x300
> (XEN) [<002c40c4>] apply_alternatives_all+0x34/0x5c
> (XEN) [<002ce3e8>] start_xen+0xcb8/0x1024
> (XEN) [<00200068>] arch/arm/arm32/head.o#primary_switched+0xc/0x1c
>
> The interrupts will be disabled by the state machine in stop_machine_run(),
> hence why the ASSERT is hit.
>
> For now the patch extending the checks has been reverted, but it would
> be good to re-introduce it (allocation with interrupts disabled is not
> desirable).
We definitely should re-apply that patch once the one here went in.
Jan
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