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    SubjectRE: [PATCH v3 6/6] PCI: hv: fix 2 hang issues in hv_compose_msi_msg()
    Date
    > -----Original Message-----
    > From: Dexuan Cui
    > Sent: Tuesday, March 6, 2018 10:22 AM
    > To: bhelgaas@google.com; linux-pci@vger.kernel.org; KY Srinivasan <kys@microsoft.com>;
    > Stephen Hemminger <sthemmin@microsoft.com>; olaf@aepfle.de; apw@canonical.com;
    > jasowang@redhat.com
    > Cc: linux-kernel@vger.kernel.org; driverdev-devel@linuxdriverproject.org; Haiyang Zhang
    > <haiyangz@microsoft.com>; vkuznets@redhat.com; marcelo.cerri@canonical.com; Michael
    > Kelley (EOSG) <Michael.H.Kelley@microsoft.com>; Dexuan Cui <decui@microsoft.com>;
    > stable@vger.kernel.org; Jack Morgenstein <jackm@mellanox.com>
    > Subject: [PATCH v3 6/6] PCI: hv: fix 2 hang issues in hv_compose_msi_msg()
    >
    > 1. With the patch "x86/vector/msi: Switch to global reservation mode"
    > (4900be8360), the recent v4.15 and newer kernels always hang for 1-vCPU
    > Hyper-V VM with SR-IOV. This is because when we reach hv_compose_msi_msg()
    > by request_irq() -> request_threaded_irq() -> __setup_irq()->irq_startup()
    > -> __irq_startup() -> irq_domain_activate_irq() -> ... ->
    > msi_domain_activate() -> ... -> hv_compose_msi_msg(), local irq is
    > disabled in __setup_irq().
    >
    > Fix this by polling the channel.
    >
    > 2. If the host is ejecting the VF device before we reach
    > hv_compose_msi_msg(), in a UP VM, we can hang in hv_compose_msi_msg()
    > forever, because at this time the host doesn't respond to the
    > CREATE_INTERRUPT request. This issue also happens to old kernels like
    > v4.14, v4.13, etc.
    >
    > Fix this by polling the channel for the PCI_EJECT message and
    > hpdev->state, and by checking the PCI vendor ID.
    >
    > Note: actually the above issues also happen to a SMP VM, if
    > "hbus->hdev->channel->target_cpu == smp_processor_id()" is true.
    >
    > Signed-off-by: Dexuan Cui <decui@microsoft.com>
    > Tested-by: Adrian Suhov <v-adsuho@microsoft.com>
    > Tested-by: Chris Valean <v-chvale@microsoft.com>
    > Cc: stable@vger.kernel.org
    > Cc: Stephen Hemminger <sthemmin@microsoft.com>
    > Cc: K. Y. Srinivasan <kys@microsoft.com>
    > Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
    > Cc: Jack Morgenstein <jackm@mellanox.com>
    > ---
    > drivers/pci/host/pci-hyperv.c | 58 ++++++++++++++++++++++++++++++++++++++++++-
    > 1 file changed, 57 insertions(+), 1 deletion(-)
    >

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

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