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From: Thomas Gleixner <tglx@linutronix.de>
To: David Woodhouse <dwmw2@infradead.org>, x86@kernel.org
Cc: iommu <iommu@lists.linux-foundation.org>,
	kvm <kvm@vger.kernel.org>,
	linux-hyperv@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 09/13] x86/irq: Add x86_non_ir_cpumask
Date: Tue, 06 Oct 2020 23:42:25 +0200
Message-ID: <87ft6r58vy.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20201005152856.974112-9-dwmw2@infradead.org>

On Mon, Oct 05 2020 at 16:28, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
>
> This is the mask of CPUs to which IRQs can be delivered without interrupt
> remapping.
>  
> +/* Mask of CPUs which can be targeted by non-remapped interrupts. */
> +cpumask_t x86_non_ir_cpumask = { CPU_BITS_ALL };

What?

>  #ifdef CONFIG_X86_32
>  
>  /*
> @@ -1838,6 +1841,7 @@ static __init void x2apic_enable(void)
>  static __init void try_to_enable_x2apic(int remap_mode)
>  {
>  	u32 apic_limit = 0;
> +	int i;
>  
>  	if (x2apic_state == X2APIC_DISABLED)
>  		return;
> @@ -1880,6 +1884,14 @@ static __init void try_to_enable_x2apic(int remap_mode)
>  	if (apic_limit)
>  		x2apic_set_max_apicid(apic_limit);
>  
> +	/* Build the affinity mask for interrupts that can't be remapped. */
> +	cpumask_clear(&x86_non_ir_cpumask);
> +	i = min_t(unsigned int, num_possible_cpus() - 1, apic_limit);
> +	for ( ; i >= 0; i--) {
> +		if (cpu_physical_id(i) <= apic_limit)
> +			cpumask_set_cpu(i, &x86_non_ir_cpumask);
> +	}

Blink. If the APIC id is not linear with the cpu numbers then this
results in a reduced addressable set of CPUs. WHY?

> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index aa9a3b54a96c..4d0ef46fedb9 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -2098,6 +2098,8 @@ static int mp_alloc_timer_irq(int ioapic, int pin)
>  		struct irq_alloc_info info;
>  
>  		ioapic_set_alloc_attr(&info, NUMA_NO_NODE, 0, 0);
> +		if (domain->parent == x86_vector_domain)
> +			info.mask = &x86_non_ir_cpumask;

We are not going to sprinkle such domain checks all over the
place. Again, the mask is a property of the interrupt domain.

Thanks,

        tglx

  reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-05 15:28 [PATCH 0/13] Fix per-domain IRQ affinity, allow >255 CPUs on x86 without IRQ remapping David Woodhouse
2020-10-05 15:28 ` [PATCH 01/13] x86/apic: Use x2apic in guest kernels even with unusable CPUs David Woodhouse
2020-10-05 15:28   ` [PATCH 02/13] x86/msi: Only use high bits of MSI address for DMAR unit David Woodhouse
2020-10-06 20:45     ` Thomas Gleixner
2020-10-05 15:28   ` [PATCH 03/13] x86/ioapic: Handle Extended Destination ID field in RTE David Woodhouse
2020-10-05 15:28   ` [PATCH 04/13] x86/apic: Support 15 bits of APIC ID in IOAPIC/MSI where available David Woodhouse
2020-10-05 15:28   ` [PATCH 05/13] genirq: Prepare for default affinity to be passed to __irq_alloc_descs() David Woodhouse
2020-10-06 21:01     ` Thomas Gleixner
2020-10-06 21:07       ` David Woodhouse
2020-10-05 15:28   ` [PATCH 06/13] genirq: Add default_affinity argument " David Woodhouse
2020-10-06 21:06     ` Thomas Gleixner
2020-10-05 15:28   ` [PATCH 07/13] irqdomain: Add max_affinity argument to irq_domain_alloc_descs() David Woodhouse
2020-10-06 21:26     ` Thomas Gleixner
2020-10-07  7:19       ` David Woodhouse
2020-10-07 13:37         ` Thomas Gleixner
2020-10-07 14:10           ` David Woodhouse
2020-10-07 15:57             ` Thomas Gleixner
2020-10-07 16:11               ` David Woodhouse
2020-10-07 20:53                 ` Thomas Gleixner
2020-10-08  7:21               ` David Woodhouse
2020-10-08  9:34                 ` Thomas Gleixner
2020-10-08 11:10                   ` David Woodhouse
2020-10-08 12:40                     ` Thomas Gleixner
2020-10-09  7:54                       ` David Woodhouse
2020-10-05 15:28   ` [PATCH 08/13] genirq: Add irq_domain_set_affinity() David Woodhouse
2020-10-06 21:32     ` Thomas Gleixner
2020-10-07  7:22       ` David Woodhouse
2020-10-05 15:28   ` [PATCH 09/13] x86/irq: Add x86_non_ir_cpumask David Woodhouse
2020-10-06 21:42     ` Thomas Gleixner [this message]
2020-10-07  7:25       ` David Woodhouse
2020-10-05 15:28   ` [PATCH 10/13] x86/irq: Limit IOAPIC and MSI domains' affinity without IR David Woodhouse
2020-10-06 21:54     ` Thomas Gleixner
2020-10-07  7:48       ` David Woodhouse
2020-10-07 12:59         ` Thomas Gleixner
2020-10-07 13:08           ` David Woodhouse
2020-10-07 14:05             ` Thomas Gleixner
2020-10-07 14:23               ` David Woodhouse
2020-10-07 16:02                 ` Thomas Gleixner
2020-10-07 16:15                   ` David Woodhouse
2020-10-07 15:05               ` David Woodhouse
2020-10-07 15:25                 ` Thomas Gleixner
2020-10-07 15:46                   ` David Woodhouse
2020-10-07 17:23                     ` Thomas Gleixner
2020-10-07 17:34                       ` David Woodhouse
2020-10-05 15:28   ` [PATCH 11/13] x86/smp: Allow more than 255 CPUs even without interrupt remapping David Woodhouse
2020-10-05 15:28   ` [PATCH 12/13] iommu/irq_remapping: Kill most of hyperv-iommu.c now it's redundant David Woodhouse
2020-10-05 15:28   ` [PATCH 13/13] x86/kvm: Add KVM_FEATURE_MSI_EXT_DEST_ID David Woodhouse
2020-10-07  8:14     ` Paolo Bonzini
2020-10-07  8:59       ` David Woodhouse
2020-10-07 11:15         ` Paolo Bonzini
2020-10-07 12:04           ` David Woodhouse

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