linux-kernel - [PATCH 5.15 120/177] PCI/MSI: Mask MSI-X vectors only on success

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Date:   Mon, 20 Dec 2021 15:34:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stefan Roese <sr@...x.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Michal Simek <michal.simek@...inx.com>,
        Marek Vasut <marex@...x.de>
Subject: [PATCH 5.15 120/177] PCI/MSI: Mask MSI-X vectors only on success

From: Stefan Roese <sr@...x.de>

commit 83dbf898a2d45289be875deb580e93050ba67529 upstream.

Masking all unused MSI-X entries is done to ensure that a crash kernel
starts from a clean slate, which correponds to the reset state of the
device as defined in the PCI-E specificion 3.0 and later:

 Vector Control for MSI-X Table Entries
 --------------------------------------

 "00: Mask bit:  When this bit is set, the function is prohibited from
                 sending a message using this MSI-X Table entry.
                 ...
                 This bit’s state after reset is 1 (entry is masked)."

A Marvell NVME device fails to deliver MSI interrupts after trying to
enable MSI-X interrupts due to that masking. It seems to take the MSI-X
mask bits into account even when MSI-X is disabled.

While not specification compliant, this can be cured by moving the masking
into the success path, so that the MSI-X table entries stay in device reset
state when the MSI-X setup fails.

[ tglx: Move it into the success path, add comment and amend changelog ]

Fixes: aa8092c1d1f1 ("PCI/MSI: Mask all unused MSI-X entries")
Signed-off-by: Stefan Roese <sr@...x.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-pci@...r.kernel.org
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Michal Simek <michal.simek@...inx.com>
Cc: Marek Vasut <marex@...x.de>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20211210161025.3287927-1-sr@denx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/pci/msi.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -721,9 +721,6 @@ static int msix_capability_init(struct p
 		goto out_disable;
 	}
 
-	/* Ensure that all table entries are masked. */
-	msix_mask_all(base, tsize);
-
 	ret = msix_setup_entries(dev, base, entries, nvec, affd);
 	if (ret)
 		goto out_disable;
@@ -750,6 +747,16 @@ static int msix_capability_init(struct p
 	/* Set MSI-X enabled bits and unmask the function */
 	pci_intx_for_msi(dev, 0);
 	dev->msix_enabled = 1;
+
+	/*
+	 * Ensure that all table entries are masked to prevent
+	 * stale entries from firing in a crash kernel.
+	 *
+	 * Done late to deal with a broken Marvell NVME device
+	 * which takes the MSI-X mask bits into account even
+	 * when MSI-X is disabled, which prevents MSI delivery.
+	 */
+	msix_mask_all(base, tsize);
 	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
 
 	pcibios_free_irq(dev);