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List:       libvir-list
Subject:    Re: [libvirt] [PATCH 6/6] virpci: Allow greater PCI domain value in virPCIDeviceAddressIsValid
From:       Ján Tomko <jtomko () redhat ! com>
Date:       2019-07-31 10:41:38
Message-ID: 20190731104138.GK14908 () lpt
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On Wed, Jul 31, 2019 at 10:32:24AM +0200, Michal Privoznik wrote:
>There is no restriction on maximum value of PCI domain. In fact,
>Linux kernel uses plain atomic inc when assigning PCI domains:
>
>drivers/pci/pci.c:static int pci_get_new_domain_nr(void)
>drivers/pci/pci.c-{
>drivers/pci/pci.c-      return atomic_inc_return(&__domain_nr);
>drivers/pci/pci.c-}
>
>Of course, this function is called only if kernel was compiled
>without PCI domain support or ACPI did not provide PCI domain.
>
>However, QEMU still has the same restriction as us: in
>set_pci_host_devaddr() QEMU checks if domain isn't greater than
>0xffff. But one can argue that that's a QEMU limitation. We still
>want to be able to cope with other hypervisors that don't have
>this limitation (possibly).
>

I would argue that by lifting this check we fail to report the error
early for QEMU that (still) lacks the support for it.

But I doubt that the QEMU fix will be detectable in our capability
probing code, so:

>Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
>---
> docs/schemas/basictypes.rng                   | 2 +-
> src/util/virpci.c                             | 2 +-
> tests/qemuxml2argvdata/pci-domain-invalid.xml | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)

Reviewed-by: J=E1n Tomko <jtomko@redhat.com>

Jano

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