This is a note to let you know that I've just added the patch titled x86/pci/xen: Disable PCI/MSI[-X] masking for XEN_HVM guests to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-pci-xen-disable-pci-msi-masking-for-xen_hvm-guests.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 7e0815b3e09986d2fe651199363e135b9358132a Mon Sep 17 00:00:00 2001 From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Date: Thu, 28 Apr 2022 15:50:54 +0200 Subject: x86/pci/xen: Disable PCI/MSI[-X] masking for XEN_HVM guests From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> commit 7e0815b3e09986d2fe651199363e135b9358132a upstream. When a XEN_HVM guest uses the XEN PIRQ/Eventchannel mechanism, then PCI/MSI[-X] masking is solely controlled by the hypervisor, but contrary to XEN_PV guests this does not disable PCI/MSI[-X] masking in the PCI/MSI layer. This can lead to a situation where the PCI/MSI layer masks an MSI[-X] interrupt and the hypervisor grants the write despite the fact that it already requested the interrupt. As a consequence interrupt delivery on the affected device is not happening ever. Set pci_msi_ignore_mask to prevent that like it's done for XEN_PV guests already. Fixes: 809f9267bbab ("xen: map MSIs into pirqs") Reported-by: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx> Reported-by: Dusty Mabe <dustymabe@xxxxxxxxxx> Reported-by: Salvatore Bonaccorso <carnil@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Tested-by: Noah Meyerhans <noahm@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/87tuaduxj5.ffs@tglx [nmeyerha@xxxxxxxxxx: backported to 4.19] Signed-off-by: Noah Meyerhans <nmeyerha@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/pci/xen.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/arch/x86/pci/xen.c +++ b/arch/x86/pci/xen.c @@ -441,6 +441,11 @@ void __init xen_msi_init(void) x86_msi.setup_msi_irqs = xen_hvm_setup_msi_irqs; x86_msi.teardown_msi_irq = xen_teardown_msi_irq; + /* + * With XEN PIRQ/Eventchannels in use PCI/MSI[-X] masking is solely + * controlled by the hypervisor. + */ + pci_msi_ignore_mask = 1; } #endif Patches currently in stable-queue which might be from tglx@xxxxxxxxxxxxx are queue-4.19/x86-pci-xen-disable-pci-msi-masking-for-xen_hvm-guests.patch