RE: [PATCH v3 6/6] PCI: hv: fix 2 hang issues in hv_compose_msi_msg()

["Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>]

> -----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>