Re: [RFC PATCH 2/6] xen/public: arch-arm: reserve resources for virtio-pci

[Julien Grall <julien@xxxxxxx>]

Hi Sergiy,

On 17/11/2023 13:19, Sergiy Kibrik wrote:
> > > > > + */
> > > > > +#define GUEST_VIRTIO_PCI_ECAM_BASE          xen_mk_ullong(0x33000000)
> > > > > +#define GUEST_VIRTIO_PCI_TOTAL_ECAM_SIZE    xen_mk_ullong(0x01000000)
> > > > > +#define GUEST_VIRTIO_PCI_HOST_ECAM_SIZE     xen_mk_ullong(0x00200000)
> > > > > +
> > > > > +/* 64 MB is reserved for virtio-pci memory */
> > > > > +#define GUEST_VIRTIO_PCI_ADDR_TYPE_MEM    xen_mk_ullong(0x02000000)
> > > > > +#define GUEST_VIRTIO_PCI_MEM_ADDR         xen_mk_ullong(0x34000000)
> > > > > +#define GUEST_VIRTIO_PCI_MEM_SIZE         xen_mk_ullong(0x04000000)
> > > > > +
> > > > >    /*
> > > > >     * 16MB == 4096 pages reserved for guest to use as a region to 
> > > > > map its
> > > > >     * grant table in.
> > > > > @@ -476,6 +489,11 @@ typedef uint64_t xen_callback_t;
> > > > >    #define GUEST_MAGIC_BASE  xen_mk_ullong(0x39000000)
> > > > >    #define GUEST_MAGIC_SIZE  xen_mk_ullong(0x01000000)
> > > > > +/* 64 MB is reserved for virtio-pci Prefetch memory */
> > > > This doesn't seem a lot depending on your use case. Can you details how
> > > > you can up with "64 MB"?
> > > the same calculation as it was done configuration space. It was observed
> > > that only 16K is used per virtio-pci device (maybe it can be bigger for
> > > usual PCI device, I don't know). Please look at the example of DomU log
> > > below (to strings that contain "*BAR 4: assigned*"):
> > What about virtio-gpu? I would expect a bit more memory is necessary 
> > for that use case.
> > Any case, what I am looking for is for some explanation in the commit 
> > message of the limits. I don't particularly care about the exact limit 
> > because this is not part of a stable ABI.
> sure, I'll put a bit more explanation in both comment and commit 
> message. Should I post updated patch series, with updated resources and 
> without patch #5, or shall we wait for some more comments here?
I would wait for comments before posting in particular if you haven't 
yet received any comment on the tools side.
Cheers,

--
Julien Grall