On Tue, Sep 24, 2024 at 05:35:20PM +0100, Julien Grall wrote: > Hi Edgar, > > On 24/09/2024 17:23, Edgar E. Iglesias wrote: > > From: "Edgar E. Iglesias" <edgar.igles...@amd.com> > > > > Reserve memory ranges and interrupt lines for an externally > > emulated PCI controller (e.g by QEMU) dedicated to hosting > > Virtio devices and potentially other emulated devices. > > > > Signed-off-by: Edgar E. Iglesias <edgar.igles...@amd.com> > > --- > > xen/include/public/arch-arm.h | 17 +++++++++++++++++ > > 1 file changed, 17 insertions(+) > > > > diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h > > index e19f0251a6..654b827715 100644 > > --- a/xen/include/public/arch-arm.h > > +++ b/xen/include/public/arch-arm.h > > @@ -494,6 +494,20 @@ typedef uint64_t xen_callback_t; > > #define GUEST_RAM1_BASE xen_mk_ullong(0x0200000000) /* 952GB of RAM @ > > 8GB */ > > #define GUEST_RAM1_SIZE xen_mk_ullong(0xee00000000) > > +/* Virtio PCI - Ordered by decreasing size to keep things aligned */ > > +#define GUEST_VIRTIO_PCI_PREFETCH_MEM_TYPE xen_mk_ullong(0x43000000) > > +#define GUEST_VIRTIO_PCI_PREFETCH_MEM_BASE xen_mk_ullong(0x0f000000000) > > +#define GUEST_VIRTIO_PCI_PREFETCH_MEM_SIZE xen_mk_ullong(0x100000000) > > + > > +#define GUEST_VIRTIO_PCI_ECAM_BASE > > (GUEST_VIRTIO_PCI_PREFETCH_MEM_BASE + \ > > + > > GUEST_VIRTIO_PCI_PREFETCH_MEM_SIZE) > > +#define GUEST_VIRTIO_PCI_ECAM_SIZE xen_mk_ullong(0x10000000) > > + > > +#define GUEST_VIRTIO_PCI_MEM_TYPE xen_mk_ullong(0x02000000) > > +#define GUEST_VIRTIO_PCI_MEM_BASE (GUEST_VIRTIO_PCI_ECAM_BASE + \ > > + GUEST_VIRTIO_PCI_ECAM_SIZE) > > +#define GUEST_VIRTIO_PCI_MEM_SIZE xen_mk_ullong(0x00002000000) > > Why is this specific to virtio PCI? However, I am not entirely convinced we > should have a second PCI hostbridge exposed to the guest for a few reasons: > 1. This require to reserve yet another range in the address space (could > be solved with a more dynamic layout) > 2. From your instructions, the guest needs to explicitly do a PCI rescan. > > So rather than having a second hostbridge, have you considered to extend the > existing hostbridge (implemented in Xen) to support a mix of physical PCI > device and virtual one? >
Thanks Julien, It's briefly come up in a couple of discussions but I haven't looked carefully at it. It is a good idea and it's probably worth prototyping to see what the gaps are in hypercall interfaces, QEMU support etc. Cheers, Edgar
