Messages in this thread | | | Date | Fri, 19 May 2023 14:41:18 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling |
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On Fri, May 19, 2023 at 12:10:26PM +0200, Marek Marczykowski-Górecki wrote: > While I would say PCI passthrough is not very common for PV guests, can > the decision about xen-swiotlb be delayed until you can enumerate > xenstore to check if there are any PCI devices connected (and not > allocate xen-swiotlb by default if there are none)? This would > still not cover the hotplug case (in which case, you'd need to force it > with a cmdline), but at least you wouldn't loose much memory just > because one of your VMs may use PCI passthrough (so, you have it enabled > in your kernel).
How early can we query xenstore? We'd need to do this before setting up DMA for any device.
The alternative would be to finally merge swiotlb-xen into swiotlb, in which case we might be able to do this later. Let me see what I can do there.
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