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    Subject[PATCH 4.14 01/23] x86/pci/xen: Disable PCI/MSI[-X] masking for XEN_HVM guests
    Date
    From: Thomas Gleixner <tglx@linutronix.de>

    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@linux.microsoft.com>
    Reported-by: Dusty Mabe <dustymabe@redhat.com>
    Reported-by: Salvatore Bonaccorso <carnil@debian.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Noah Meyerhans <noahm@debian.org>
    Cc: stable@vger.kernel.org
    Link: https://lore.kernel.org/r/87tuaduxj5.ffs@tglx
    [nmeyerha@amazon.com: backported to 4.14]
    Signed-off-by: Noah Meyerhans <nmeyerha@amazon.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/pci/xen.c | 5 +++++
    1 file changed, 5 insertions(+)

    --- a/arch/x86/pci/xen.c
    +++ b/arch/x86/pci/xen.c
    @@ -442,6 +442,11 @@ 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


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