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

From: Vincent Whitchurch
Date: Thu Jan 26 2023 - 05:48:05 EST


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@xxxxxxxx>
---
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@xxxxxxxx>