linux-kernel - [PATCH] um-virt-pci: Make max delay configurable

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Date:   Thu, 26 Jan 2023 11:47:10 +0100
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>
CC:     <linux-um@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <kernel@...s.com>, Vincent Whitchurch <vincent.whitchurch@...s.com>
Subject: [PATCH] um-virt-pci: Make max delay configurable

There is a hard coded maximum time for which the driver busy-loops
waiting for a response from the virtio device.  This default time may be
too short for some systems, so make it a module parameter so that it can
be set via the kernel command line.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 arch/um/drivers/virt-pci.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
index 3ac220dafec4..33183f6f9f2a 100644
--- a/arch/um/drivers/virt-pci.c
+++ b/arch/um/drivers/virt-pci.c
@@ -54,7 +54,8 @@ static struct irq_domain *um_pci_inner_domain;
 static struct irq_domain *um_pci_msi_domain;
 static unsigned long um_pci_msi_used[BITS_TO_LONGS(MAX_MSI_VECTORS)];
 
-#define UM_VIRT_PCI_MAXDELAY 40000
+static unsigned int um_pci_max_delay_us = 40000;
+module_param_named(max_delay_us, um_pci_max_delay_us, uint, 0644);
 
 struct um_pci_message_buffer {
 	struct virtio_pcidev_msg hdr;
@@ -155,7 +156,7 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
 			kfree(completed);
 
 		if (WARN_ONCE(virtqueue_is_broken(dev->cmd_vq) ||
-			      ++delay_count > UM_VIRT_PCI_MAXDELAY,
+			      ++delay_count > um_pci_max_delay_us,
 			      "um virt-pci delay: %d", delay_count)) {
 			ret = -EIO;
 			break;

---
base-commit: 1b929c02afd37871d5afb9d498426f83432e71c2
change-id: 20230126-uml-pci-delay-2a9c9530eeb6

Best regards,
-- 
Vincent Whitchurch <vincent.whitchurch@...s.com>