This is a note to let you know that I've just added the patch titled
hv_netvsc: Calculate correct ring size when PAGE_SIZE is not 4 Kbytes
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hv_netvsc-calculate-correct-ring-size-when-page_size-is-not-4-kbytes.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6941f67ad37d5465b75b9ffc498fcf6897a3c00e Mon Sep 17 00:00:00 2001
From: Michael Kelley <mhklinux@xxxxxxxxxxx>
Date: Mon, 22 Jan 2024 08:20:28 -0800
Subject: hv_netvsc: Calculate correct ring size when PAGE_SIZE is not 4 Kbytes
From: Michael Kelley <mhklinux@xxxxxxxxxxx>
commit 6941f67ad37d5465b75b9ffc498fcf6897a3c00e upstream.
Current code in netvsc_drv_init() incorrectly assumes that PAGE_SIZE
is 4 Kbytes, which is wrong on ARM64 with 16K or 64K page size. As a
result, the default VMBus ring buffer size on ARM64 with 64K page size
is 8 Mbytes instead of the expected 512 Kbytes. While this doesn't break
anything, a typical VM with 8 vCPUs and 8 netvsc channels wastes 120
Mbytes (8 channels * 2 ring buffers/channel * 7.5 Mbytes/ring buffer).
Unfortunately, the module parameter specifying the ring buffer size
is in units of 4 Kbyte pages. Ideally, it should be in units that
are independent of PAGE_SIZE, but backwards compatibility prevents
changing that now.
Fix this by having netvsc_drv_init() hardcode 4096 instead of using
PAGE_SIZE when calculating the ring buffer size in bytes. Also
use the VMBUS_RING_SIZE macro to ensure proper alignment when running
with page size larger than 4K.
Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x
Fixes: 7aff79e297ee ("Drivers: hv: Enable Hyper-V code to be built on ARM64")
Signed-off-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240122162028.348885-1-mhklinux@xxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/hyperv/netvsc_drv.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -44,7 +44,7 @@
static unsigned int ring_size __ro_after_init = 128;
module_param(ring_size, uint, 0444);
-MODULE_PARM_DESC(ring_size, "Ring buffer size (# of pages)");
+MODULE_PARM_DESC(ring_size, "Ring buffer size (# of 4K pages)");
unsigned int netvsc_ring_bytes __ro_after_init;
static const u32 default_msg = NETIF_MSG_DRV | NETIF_MSG_PROBE |
@@ -2805,7 +2805,7 @@ static int __init netvsc_drv_init(void)
pr_info("Increased ring_size to %u (min allowed)\n",
ring_size);
}
- netvsc_ring_bytes = ring_size * PAGE_SIZE;
+ netvsc_ring_bytes = VMBUS_RING_SIZE(ring_size * 4096);
register_netdevice_notifier(&netvsc_netdev_notifier);
Patches currently in stable-queue which might be from mhklinux@xxxxxxxxxxx are
queue-6.6/hv_netvsc-calculate-correct-ring-size-when-page_size-is-not-4-kbytes.patch
