On 14-09-2026 04:09, Wei Liu wrote: > On Fri, Sep 11, 2026 at 12:29:05PM +0200, Manivannan Sadhasivam wrote: >> On Wed, Sep 09, 2026 at 03:01:22PM +0530, Naman Jain wrote: >>> >>> >>> On 9/8/2026 5:00 PM, Sahil Chandna wrote: >>>> A guest can wait indefinitely in wait_for_response() for the host to >>>> send either a rescind message or a packet completion. If the >>>> host does not send either, the guest can remain blocked with no >>>> diagnostic indicating a reason. >>>> This was observed during a guest kernel upgrade in which the >>>> host-side application handling the PCI channel faulted, causing the >>>> guest to never receive the completion request. >>>> Add a warning in wait_for_response() when the wait exceeds >>>> a timeout so that such a hang is visible in the guest's kernel log >>>> and can be correlated with host-side state. >>>> >>>> Suggested-by: Michael Kelley <[email protected]> >>>> Signed-off-by: Sahil Chandna <[email protected]> >>>> --- >>>> Changes since v2: >>>> - Add counter based timeout instead of introducing another timer >>>> Link to v2: >>>> https://lore.kernel.org/all/[email protected]/ >>>> >>>> Changes since v1: >>>> - Removed periodic warning to one time warning in 2 minutes >>>> - Include vmbus relid and stuck PCI msg. >>>> Link to v1: >>>> https://lore.kernel.org/all/[email protected]/ >>>> drivers/pci/controller/pci-hyperv.c | 46 ++++++++++++++++++++++------- >>>> 1 file changed, 36 insertions(+), 10 deletions(-) >>>> >>>> diff --git a/drivers/pci/controller/pci-hyperv.c >>>> b/drivers/pci/controller/pci-hyperv.c >>>> index 89816a2bd7cd..bd07402c47ed 100644 >>>> --- a/drivers/pci/controller/pci-hyperv.c >>>> +++ b/drivers/pci/controller/pci-hyperv.c >>>> @@ -1040,19 +1040,38 @@ static void put_pcichild(struct hv_pci_dev *hpdev) >>>> >>>> /* >>>> * There is no good way to get notified from vmbus_onoffer_rescind(), >>>> - * so let's use polling here, since this is not a hot path. >>>> + * so let's use polling here, since this is not a hot path. If >>>> + * wait_for_response() has been polling for 2 minutes >>>> + * without either a rescind or completion, add a warning. >>>> */ >>>> +#define PCI_RESPONSE_HANG_TICKS 1200 >>>> + >>> >>> Nit, I think this variable name could be misleading, as this represents a >>> loop counter for a retry logic, but not exactly *ticks* from kernel >>> terminology. >>> >>> I would have preferred something like: PCI_RESPONSE_WARN_POLL_COUNT. Ack, I have added in v4. >>> >> >> PCI_RESPONSE_POLL_COUNT? > Hi Mani, i am inclining towards PCI_RESPONSE_WARN_POLL_COUNT as intention of change is to emit a warning when counter has exceeded a set threshold.
> Sahil, let me know if you will send out another version. If it is only > changing one macro name, I can do that. > Hi Wei, I have sent out v4. Regards, Sahil > Wei
