[v1] hw/pci: add comment explaining the reason for checking function 0 in hotplug

[PATCH] hw/pci: add comment explaining the reason for checking function 0 in hotplug

Ani Sinha posted 1 patch 11 months ago

Diff against v2
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Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20230620142551.115394-1-anisinha@redhat.com

Maintainers: "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>

There is a newer version of this series

hw/pci/pci.c | 5 +++++
1 file changed, 5 insertions(+)

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[PATCH] hw/pci: add comment explaining the reason for checking function 0 in hotplug

Posted by Ani Sinha 11 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
Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 hw/pci/pci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index bf38905b7d..847e534f68 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1179,6 +1179,11 @@ 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;
+    /*
+     * 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)) {
-- 
2.39.1

Re: [PATCH] hw/pci: add comment explaining the reason for checking function 0 in hotplug

Posted by Michael S. Tsirkin 11 months ago

On Tue, Jun 20, 2023 at 07:55:51PM +0530, Ani Sinha 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
> Signed-off-by: Ani Sinha <anisinha@redhat.com>
> ---
>  hw/pci/pci.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index bf38905b7d..847e534f68 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1179,6 +1179,11 @@ 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;
> +    /*
> +     * 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.
> +     */

bad place for the comment

>      }


stick the comment here

> else

or here

> if (dev->hotplugged &&
>                 !pci_is_vf(pci_dev) &&
>                 pci_get_function_0(pci_dev)) {
> -- 
> 2.39.1