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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>,
        Dusty Mabe <dustymabe@redhat.com>,
        Salvatore Bonaccorso <carnil@debian.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Noah Meyerhans <noahm@debian.org>,
        Noah Meyerhans <nmeyerha@amazon.com>
Subject: [PATCH 5.4 02/34] x86/pci/xen: Disable PCI/MSI[-X] masking for XEN_HVM guests
Date:   Fri,  3 Jun 2022 19:42:58 +0200
Message-Id: <20220603173816.063706442@linuxfoundation.org>
In-Reply-To: <20220603173815.990072516@linuxfoundation.org>
References: <20220603173815.990072516@linuxfoundation.org>
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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 5.4]
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