linux-kernel - Re: [PATCH v2] PCI: hv: Fix a crash in hv_pci_restore_msi

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Message-ID: <402a0ea4-7944-4f00-a06d-a14578859384@linux.intel.com>
Date:   Wed, 16 Aug 2023 11:12:01 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Dexuan Cui <decui@...rosoft.com>, tglx@...utronix.de, jgg@...pe.ca,
        bhelgaas@...gle.com, haiyangz@...rosoft.com, kw@...ux.com,
        kys@...rosoft.com, linux-hyperv@...r.kernel.org,
        linux-pci@...r.kernel.org, lpieralisi@...nel.org,
        mikelley@...rosoft.com, robh@...nel.org, wei.liu@...nel.org,
        helgaas@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: hv: Fix a crash in hv_pci_restore_msi_msg()
 during hibernation


On 8/16/2023 10:59 AM, Dexuan Cui wrote:
> When a Linux VM with an assigned PCI device runs on Hyper-V, if the PCI
> device driver is not loaded yet (i.e. MSI-X/MSI is not enabled on the
> device yet), doing a VM hibernation triggers a panic in
> hv_pci_restore_msi_msg() -> msi_lock_descs(&pdev->dev), because
> pdev->dev.msi.data is still NULL.
>
> Avoid the panic by checking if MSI-X/MSI is enabled.
>
> Fixes: dc2b453290c4 ("PCI: hv: Rework MSI handling")
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
>
> Changes in v2:
>      Replaced the test "if (!pdev->dev.msi.data)" with
> 		      "if (!pdev->msi_enabled && !pdev->msix_enabled)".
>        Thanks Michael!
>      Updated the changelog accordingly.
>
>   drivers/pci/controller/pci-hyperv.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 2d93d0c4f10d..bed3cefdaf19 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -3983,6 +3983,9 @@ static int hv_pci_restore_msi_msg(struct pci_dev *pdev, void *arg)
>   	struct msi_desc *entry;
>   	int ret = 0;
>   
> +	if (!pdev->msi_enabled && !pdev->msix_enabled)
> +		return 0;
Isn't this is a error condition? Don't you want to return error here?
> +
>   	msi_lock_descs(&pdev->dev);
>   	msi_for_each_desc(entry, &pdev->dev, MSI_DESC_ASSOCIATED) {
>   		irq_data = irq_get_irq_data(entry->irq);