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Re: [PATCH] hw/pci/pcie: Move hot plug capability check to pre_plug call
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH] hw/pci/pcie: Move hot plug capability check to pre_plug callback |
Date: |
Mon, 1 Jun 2020 23:54:16 -0400 |
On Mon, Jun 01, 2020 at 06:29:34PM +0200, Julia Suvorova wrote:
> Check for hot plug capability earlier to avoid removing devices attached
> during the initialization process.
>
> Run qemu with an unattached drive:
> -drive file=$FILE,if=none,id=drive0 \
> -device pcie-root-port,id=rp0,slot=3,bus=pcie.0,hotplug=off
> Hotplug a block device:
> device_add virtio-blk-pci,id=blk0,drive=drive0,bus=rp0
> If hotplug fails on plug_cb, drive0 will be deleted.
>
> Signed-off-by: Julia Suvorova <jusual@redhat.com>
Fixes: 0501e1aa1d32a6 ("hw/pci/pcie: Forbid hot-plug if it's disabled on the
slot")
correct?
> ---
> Hard to say if it's a bug or generally acceptable behaviour, but seems like
> hotplug_handler_plug should never fail.
>
> hw/pci/pcie.c | 19 +++++++++++--------
> 1 file changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> index f50e10b8fb..5b9c022d91 100644
> --- a/hw/pci/pcie.c
> +++ b/hw/pci/pcie.c
> @@ -407,6 +407,17 @@ static void pcie_cap_slot_plug_common(PCIDevice
> *hotplug_dev, DeviceState *dev,
> void pcie_cap_slot_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
> Error **errp)
> {
> + PCIDevice *hotplug_pdev = PCI_DEVICE(hotplug_dev);
> + uint8_t *exp_cap = hotplug_pdev->config + hotplug_pdev->exp.exp_cap;
> + uint32_t sltcap = pci_get_word(exp_cap + PCI_EXP_SLTCAP);
> +
> + /* Check if hot-plug is disabled on the slot */
> + if (dev->hotplugged && (sltcap & PCI_EXP_SLTCAP_HPC) == 0) {
> + error_setg(errp, "Hot-plug failed: unsupported by the port device
> '%s'",
> + DEVICE(hotplug_pdev)->id);
> + return;
> + }
> +
> pcie_cap_slot_plug_common(PCI_DEVICE(hotplug_dev), dev, errp);
> }
>
> @@ -415,7 +426,6 @@ void pcie_cap_slot_plug_cb(HotplugHandler *hotplug_dev,
> DeviceState *dev,
> {
> PCIDevice *hotplug_pdev = PCI_DEVICE(hotplug_dev);
> uint8_t *exp_cap = hotplug_pdev->config + hotplug_pdev->exp.exp_cap;
> - uint32_t sltcap = pci_get_word(exp_cap + PCI_EXP_SLTCAP);
> PCIDevice *pci_dev = PCI_DEVICE(dev);
>
> /* Don't send event when device is enabled during qemu machine creation:
> @@ -431,13 +441,6 @@ void pcie_cap_slot_plug_cb(HotplugHandler *hotplug_dev,
> DeviceState *dev,
> return;
> }
>
> - /* Check if hot-plug is disabled on the slot */
> - if ((sltcap & PCI_EXP_SLTCAP_HPC) == 0) {
> - error_setg(errp, "Hot-plug failed: unsupported by the port device
> '%s'",
> - DEVICE(hotplug_pdev)->id);
> - return;
> - }
> -
> /* To enable multifunction hot-plug, we just ensure the function
> * 0 added last. When function 0 is added, we set the sltsta and
> * inform OS via event notification.
> --
> 2.25.4