linux-kernel - Re: [PATCH 1/2] x86/apic: Allow reprogramming IOAPIC pins the first time for non-legacy IRQs

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Message-ID: <89a51be4-38f9-4a9e-85fb-52c48a8fd433@amd.com>
Date:   Mon, 23 Oct 2023 08:26:58 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com
Cc:     x86@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
        dlazar@...il.com, hdegoede@...hat.com
Subject: Re: [PATCH 1/2] x86/apic: Allow reprogramming IOAPIC pins the first
 time for non-legacy IRQs

On 10/19/2023 22:38, Mario Limonciello wrote:
> If the system is set up without legacy IRQs configured
> acpi_register_gsi_ioapic() still needs to be able to program the IOAPIC
> to match the values from _CRS which might not match what is already
> programmed to the IOAPIC.
> 
> Reported-by: dlazar@...il.com
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218003
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>   arch/x86/kernel/apic/io_apic.c | 8 ++------
>   1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index 00da6cf6b07d..27dd279dcc7b 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -928,12 +928,8 @@ static bool mp_check_pin_attr(int irq, struct irq_alloc_info *info)
>   {
>   	struct mp_chip_data *data = irq_get_chip_data(irq);
>   
> -	/*
> -	 * setup_IO_APIC_irqs() programs all legacy IRQs with default trigger
> -	 * and polarity attributes. So allow the first user to reprogram the
> -	 * pin with real trigger and polarity attributes.
> -	 */
> -	if (irq < nr_legacy_irqs() && data->count == 1) {
> +	/* allow the first user to reprogram the pin with real trigger and polarity */
> +	if (data->count == 1) {
>   		if (info->ioapic.is_level != data->is_level)
>   			mp_register_handler(irq, info->ioapic.is_level);
>   		data->entry.is_level = data->is_level = info->ioapic.is_level;

David mentioned it on the Bugzilla, but for the benefit of those not 
looking there, this series is confirmed to fix the problem.