linux-kernel - Re: [PATCH] xen/x86: actually allocate legacy interrupts on PV guests

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Date:	Thu, 21 Apr 2016 11:08:16 +0200
From:	Juergen Gross <jgross@...e.com>
To:	Stefano Stabellini <sstabellini@...nel.org>,
	boris.ostrovsky@...cle.com
Cc:	linux-kernel@...r.kernel.org, david.vrabel@...rix.com,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH] xen/x86: actually allocate legacy interrupts on PV guests

On 20/04/16 15:15, Stefano Stabellini wrote:
> b4ff8389ed14 is incomplete: relies on nr_legacy_irqs() to get the number
> of legacy interrupts when actually nr_legacy_irqs() returns 0 after
> probe_8259A(). Use NR_IRQS_LEGACY instead.

Would you mind describing the resulting problem? With this commit
message I'm absolutely not capable to decide whether e.g. the other
use of nr_legacy_irqs() in pci_xen_initial_domain() is correct or
not.


Juergen

> 
> Signed-off-by: Stefano Stabellini <sstabellini@...nel.org>
> 
> diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
> index beac4df..349b8ce 100644
> --- a/arch/x86/pci/xen.c
> +++ b/arch/x86/pci/xen.c
> @@ -491,8 +491,11 @@ int __init pci_xen_initial_domain(void)
>  #endif
>  	__acpi_register_gsi = acpi_register_gsi_xen;
>  	__acpi_unregister_gsi = NULL;
> -	/* Pre-allocate legacy irqs */
> -	for (irq = 0; irq < nr_legacy_irqs(); irq++) {
> +	/*
> +	 * Pre-allocate the legacy IRQs.  Use NR_LEGACY_IRQS here
> +	 * because we don't have a PIC and thus nr_legacy_irqs() is zero.
> +	 */
> +	for (irq = 0; irq < NR_IRQS_LEGACY; irq++) {
>  		int trigger, polarity;
>  
>  		if (acpi_get_override_irq(irq, &trigger, &polarity) == -1)
>