linux-kernel - Re: [PATCH v2 2/4] PCI: only build xen-pcifront in PV-enabled environments

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Date:   Fri, 17 Sep 2021 11:28:44 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jan Beulich <jbeulich@...e.com>
Cc:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "hch@....de" <hch@....de>, Konrad Wilk <konrad.wilk@...cle.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] PCI: only build xen-pcifront in PV-enabled
 environments

s/only/Only/ in subject

On Fri, Sep 17, 2021 at 12:48:03PM +0200, Jan Beulich wrote:
> The driver's module init function, pcifront_init(), invokes
> xen_pv_domain() first thing. That construct produces constant "false"
> when !CONFIG_XEN_PV. Hence there's no point building the driver in
> non-PV configurations.

Thanks for these bread crumbs.  xen_domain_type is set to
XEN_PV_DOMAIN only by xen_start_kernel() in enlighten_pv.c, which is
only built when CONFIG_XEN_PV=y, so even I can verify this :)

> Drop the (now implicit and generally wrong) X86 dependency: At present,
> XEN_PV con only be set when X86 is also enabled. In general an
> architecture supporting Xen PV (and PCI) would want to have this driver
> built.

s/con only/can only/

> Signed-off-by: Jan Beulich <jbeulich@...e.com>
> Reviewed-by: Stefano Stabellini <sstabellini@...nel.org>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
> v2: Title and description redone.
> 
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -110,7 +110,7 @@ config PCI_PF_STUB
>  
>  config XEN_PCIDEV_FRONTEND
>  	tristate "Xen PCI Frontend"
> -	depends on X86 && XEN
> +	depends on XEN_PV
>  	select PCI_XEN
>  	select XEN_XENBUS_FRONTEND
>  	default y
>