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Re: [PATCH] x86/xen: call xen_set_upcall_vector() only after local apic setup
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 14 Nov 2022 10:32:48 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx
- Delivery-date: Mon, 14 Nov 2022 09:33:02 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 12.11.2022 14:23, Juergen Gross wrote:
> Calling xen_set_upcall_vector() before the local APIC has been
> initialized results in warnings when setting up the local APIC:
>
> [ 0.037322] APIC: Stale IRR: 00080000, ...
>
> Avoid this problem by moving the call of xen_set_upcall_vector() for
> APs from xen_cpu_up_prepare_hvm() to a new hotplug callback called on
> the AP before interrupts are enabled and after the local APIC has been
> initialized. There is already a Xen specific hotplug state defined at
> a matching position, but right now it is specific to Arm. So rename
> the CPUHP_AP_ARM_XEN_STARTING to CPUHP_AP_XEN_STARTING and use it for
> x86, too.
>
> On the boot processor use the x86_init.irqs.intr_mode_init hook to
> call xen_set_upcall_vector() only after the local APIC initialization.
> As interrupts are on already at the time when the hook is being used,
> modify xen_init_setup_upcall_vector() to disable interrupts. This is
> needed as the xen_percpu_upcall flag is set only after the callback
> has been registered, and the flag is needed for correctly acknowledging
> an interrupt.
>
> Fixes: b1c3497e604d ("x86/xen: Add support for
> HVMOP_set_evtchn_upcall_vector")
> Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Just to mention it here - as per [1] the issue may instead result from
hypervisor misbehavior, so I guess we want to investigate that route
first.
Jan
[1] https://lists.xen.org/archives/html/xen-devel/2022-11/msg00783.html
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