hw/pci: add comment to explain checking for available function 0 in pci hotplug

[PATCH RESEND] hw/pci: add comment to explain checking for available function 0 in pci hotplug

Posted by Ani Sinha 2 years, 5 months ago

This change is cosmetic. A comment is added explaining why we need to check for
the availability of function 0 when we hotplug a device.

CC: mst@redhat.com
CC: mjt@tls.msk.ru
Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 hw/pci/pci.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index e2eb4c3b4a..6db18dfe46 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1180,9 +1180,14 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev,
                    PCI_SLOT(devfn), PCI_FUNC(devfn), name,
                    bus->devices[devfn]->name, bus->devices[devfn]->qdev.id);
         return NULL;
-    } else if (dev->hotplugged &&
-               !pci_is_vf(pci_dev) &&
-               pci_get_function_0(pci_dev)) {
+    } /*
+       * Populating function 0 triggers a scan from the guest that
+       * exposes other non-zero functions. Hence we need to ensure that
+       * function 0 wasn't added yet.
+       */
+    else if (dev->hotplugged &&
+             !pci_is_vf(pci_dev) &&
+             pci_get_function_0(pci_dev)) {
         error_setg(errp, "PCI: slot %d function 0 already occupied by %s,"
                    " new func %s cannot be exposed to guest.",
                    PCI_SLOT(pci_get_function_0(pci_dev)->devfn),
-- 
2.39.1

Re: [PATCH RESEND] hw/pci: add comment to explain checking for available function 0 in pci hotplug

Posted by Ani Sinha 2 years, 5 months ago


> On 11-Jul-2023, at 12:33 PM, Ani Sinha <anisinha@redhat.com> wrote:
> 
> This change is cosmetic. A comment is added explaining why we need to check for
> the availability of function 0 when we hotplug a device.
> 
> CC: mst@redhat.com
> CC: mjt@tls.msk.ru
> Signed-off-by: Ani Sinha <anisinha@redhat.com>


Can we merge this while we are still in rc0?

> ---
> hw/pci/pci.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index e2eb4c3b4a..6db18dfe46 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1180,9 +1180,14 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev,
>                    PCI_SLOT(devfn), PCI_FUNC(devfn), name,
>                    bus->devices[devfn]->name, bus->devices[devfn]->qdev.id);
>         return NULL;
> -    } else if (dev->hotplugged &&
> -               !pci_is_vf(pci_dev) &&
> -               pci_get_function_0(pci_dev)) {
> +    } /*
> +       * Populating function 0 triggers a scan from the guest that
> +       * exposes other non-zero functions. Hence we need to ensure that
> +       * function 0 wasn't added yet.
> +       */
> +    else if (dev->hotplugged &&
> +             !pci_is_vf(pci_dev) &&
> +             pci_get_function_0(pci_dev)) {
>         error_setg(errp, "PCI: slot %d function 0 already occupied by %s,"
>                    " new func %s cannot be exposed to guest.",
>                    PCI_SLOT(pci_get_function_0(pci_dev)->devfn),
> -- 
> 2.39.1
>