linux-kernel - Re: [patch RFC 24/38] x86/xen: Consolidate XEN-MSI init

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Date:   Mon, 24 Aug 2020 06:59:05 +0200
From:   Jürgen Groß <jgross@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, linux-hyperv@...r.kernel.org,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Jon Derrick <jonathan.derrick@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Wei Liu <wei.liu@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Steve Wahl <steve.wahl@....com>,
        Dimitri Sivanich <sivanich@....com>,
        Russ Anderson <rja@....com>, linux-pci@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        xen-devel@...ts.xenproject.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Megha Dey <megha.dey@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jacob Pan <jacob.jun.pan@...el.com>,
        Baolu Lu <baolu.lu@...el.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [patch RFC 24/38] x86/xen: Consolidate XEN-MSI init

On 21.08.20 02:24, Thomas Gleixner wrote:
> X86 cannot store the irq domain pointer in struct device without breaking
> XEN because the irq domain pointer takes precedence over arch_*_msi_irqs()
> fallbacks.
> 
> To achieve this XEN MSI interrupt management needs to be wrapped into an
> irq domain.
> 
> Move the x86_msi ops setup into a single function to prepare for this.
> 
> Signed-off-by: Thomas Gleixner<tglx@...utronix.de>
> ---
>   arch/x86/pci/xen.c |   51 ++++++++++++++++++++++++++++++++-------------------
>   1 file changed, 32 insertions(+), 19 deletions(-)
> 
> --- a/arch/x86/pci/xen.c
> +++ b/arch/x86/pci/xen.c
> @@ -371,7 +371,10 @@ static void xen_initdom_restore_msi_irqs
>   		WARN(ret && ret != -ENOSYS, "restore_msi -> %d\n", ret);
>   	}
>   }
> -#endif
> +#else /* CONFIG_XEN_DOM0 */
> +#define xen_initdom_setup_msi_irqs	NULL
> +#define xen_initdom_restore_msi_irqs	NULL
> +#endif /* !CONFIG_XEN_DOM0 */
>   
>   static void xen_teardown_msi_irqs(struct pci_dev *dev)
>   {
> @@ -403,7 +406,31 @@ static void xen_teardown_msi_irq(unsigne
>   	WARN_ON_ONCE(1);
>   }
>   
> -#endif
> +static __init void xen_setup_pci_msi(void)
> +{
> +	if (xen_initial_domain()) {
> +		x86_msi.setup_msi_irqs = xen_initdom_setup_msi_irqs;
> +		x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
> +		x86_msi.restore_msi_irqs = xen_initdom_restore_msi_irqs;
> +		pci_msi_ignore_mask = 1;

This is wrong, as a PVH initial domain shouldn't do the pv settings.

The "if (xen_initial_domain())" should be inside the pv case, like:

if (xen_pv_domain()) {
	if (xen_initial_domain()) {
		...
	} else {
		...
	}
} else if (xen_hvm_domain()) {
	...

Juergen