Re: [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling

[Juergen Gross <jgross@xxxxxxxx>]

On 09.06.23 17:38, Juergen Gross wrote:
> On 07.06.23 15:12, Christoph Hellwig wrote:
> > On Mon, May 22, 2023 at 10:37:09AM +0200, Juergen Gross wrote:
> > > In normal cases PCI passthrough in PV guests requires to start the guest
> > > with e820_host=1. So it should be rather easy to limit allocating the
> > > 64MB in PV guests to the cases where the memory map has non-RAM regions
> > > especially in the first 1MB of the memory.
> > >
> > > This will cover even hotplug cases. The only case not covered would be a
> > > guest started with e820_host=1 even if no PCI passthrough was planned.
> > > But this should be rather rare (at least I hope so).
> > So is this an ACK for the patch and can we go ahead with it?
> As long as above mentioned check of the E820 map is done, yes.
>
> If you want I can send a diff to be folded into your patch on Monday.
Attached is a patch for adding a new flag xen_pv_pci_possible. You can
either add the patch to your series or merge it into your patch 2.

You need to modify your patch like this:

@@ -111,7 +90,10 @@ static inline void __init pci_xen_swiotlb_init(void)
 void __init pci_iommu_alloc(void)
 {
        if (xen_pv_domain()) {
-               if (xen_initial_domain() || x86_swiotlb_enable)
+               if (xen_initial_domain() ||
+                   (IS_ENABLED(CONFIG_XEN_PCIDEV_FRONTEND) &&
+                    xen_pv_pci_possible) ||
+                   x86_swiotlb_enable)
                        pci_xen_swiotlb_init();
                return;
        }


Juergen

Attachment: 0001-xen-pci-add-flag-for-PCI-passthrough-being-possible.patch
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