> From: Dexuan Cui > Sent: Wednesday, March 7, 2018 13:40 > To: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > Cc: bhelgaas@xxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; KY Srinivasan > <kys@xxxxxxxxxxxxx>; Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>; > olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx; Haiyang > Zhang <haiyangz@xxxxxxxxxxxxx>; vkuznets@xxxxxxxxxx; > marcelo.cerri@xxxxxxxxxxxxx; Michael Kelley (EOSG) > <Michael.H.Kelley@xxxxxxxxxxxxx>; stable@xxxxxxxxxxxxxxx; Jack > Morgenstein <jackm@xxxxxxxxxxxx> > Subject: RE: [PATCH v3 6/6] PCI: hv: fix 2 hang issues in hv_compose_msi_msg() > > > From: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > > Sent: Wednesday, March 7, 2018 04:35 > > On Tue, Mar 06, 2018 at 06:21:56PM +0000, Dexuan Cui wrote: > > > 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. > > > > If you are fixing a problem you should report what commit you are fixing > > with a Fixes: tag and add a CC: stable@xxxxxxxxxxxxxxx to the commit log > > to send it to stable kernels to which it should be applied; mentioning > > kernel versions in the commit log is useless and should be omitted. > > Hi Lorenzo, > Thanks for your comments! > This patch does have a "Cc: stable@xxxxxxxxxxxxxxx" in the sign-off area. :-) > > Here the patch is made to resolve 2 issues: > #1 is triggered by the x86 global reservation mode (4900be8360) patch. > 4900be8360 in itself is good. It's just that drivers/pci/host/pci-hyperv.c > should be fixed. > > #2 is a longstanding issue since the first day the pci-hyperv driver was > accepted into the kernel. > > So IMO actually we don't really need to add a Fixes: tag, which is usually > used to specify a specific commit that introduces a bug that is being fixed. > > > Side note: you should not have stable@xxxxxxxxxxxxxxx in the email > > addresses CC list you are sending the patches to (you mark patches for > > stable by adding an appropriate CC tag in the commit log). > > Sorry, I didn't know this, but actually I didn't add stable@xxxxxxxxxxxxxxx > manually. Instead I used "git send-email" to send this patchset, and it told > me "The Cc list above has been expanded by additional addresses found > in the patch commit message." > > I didn't find a way to disable this behavior of "git send-email" by checking > its manual and googling it. This is strange. > > > Here: > > > > git.kernel.org/.../Documentation/process/stable-kernel-rules.rst > > > > Last but not least, most of the patches in this series do not justify > > sending them to stable kernels at all so you should remove the > > corresponding tag from the patches. > > I hope at least these 2 patches can go into the stable kernels: > [PATCH v3 3/6] PCI: hv: serialize the present/eject work items > [PATCH v3 6/6] PCI: hv: fix 2 hang issues in hv_compose_msi_msg() > Especially the second one, which fixes a real hang issue for UP virtual > machines running v4.15 and newer. > And, IMO the patches are small enough (<100 lines) , but definitely > the maintainers make the final call. > > > > > Thanks, > > Lorenzo > > > > > 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@xxxxxxxxxxxxx> > > > Tested-by: Adrian Suhov <v-adsuho@xxxxxxxxxxxxx> > > > Tested-by: Chris Valean <v-chvale@xxxxxxxxxxxxx> > > > Cc: stable@xxxxxxxxxxxxxxx > > > Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx> > > > Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx> > > > Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > > > Cc: Jack Morgenstein <jackm@xxxxxxxxxxxx> > > > --- > > > drivers/pci/host/pci-hyperv.c | 58 > > > Thanks, > -- Dexuan Hi Lorenzo, Bjorn, and all, Do you need more ACKs? Currently Michael and Haiyang reviewed and ack'd the patchset. Should I send a v4 that just removes the "CC: stable@xxxxxxxxxxxxxxx" tag for patches 1, 2, 4 and 5? I tend to avoid a v4 as I supppose it would be easier if you just remove the tags if you belive it's necessary (IMHO all the 6 paches are not big and it would be great if we can have all of them in the old stable kernels, but I respect your decision). Please let me know if I missed something when addressing the comments, and if I should send a v4. Thanks! -- Dexuan
