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

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Message-ID: <BYAPR21MB16888FCA41CEB8569685FBB1D715A@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Wed, 16 Aug 2023 20:10:25 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "kw@...ux.com" <kw@...ux.com>, KY Srinivasan <kys@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        "robh@...nel.org" <robh@...nel.org>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "helgaas@...nel.org" <helgaas@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] PCI: hv: Fix a crash in hv_pci_restore_msi_msg()
 during hibernation

From: Dexuan Cui <decui@...rosoft.com> Sent: Wednesday, August 16, 2023 11:00 AM
> 
> 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;
> +
>  	msi_lock_descs(&pdev->dev);
>  	msi_for_each_desc(entry, &pdev->dev, MSI_DESC_ASSOCIATED) {
>  		irq_data = irq_get_irq_data(entry->irq);
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>