git: 2c713c35b430 - stable/15 - mlx5ib: advertise write-combining support for dynamic BlueFlame UARs

The branch stable/15 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=2c713c35b4304eca5e940db6eed2519071e3a87e

commit 2c713c35b4304eca5e940db6eed2519071e3a87e
Author:     Ariel Ehrenberg <aehrenberg@nvidia.com>
AuthorDate: 2026-06-08 10:56:04 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-07-20 20:26:08 +0000

    mlx5ib: advertise write-combining support for dynamic BlueFlame UARs
    
    (cherry picked from commit 80902b8b7cd409ade11048dc78212e7d43475c65)
---
 sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c b/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c
index c6175570734c..6e7eceb0755a 100644
--- a/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c
+++ b/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c
@@ -3579,6 +3579,16 @@ static void *mlx5_ib_add(struct mlx5_core_dev *mdev)
 
 	dev->mdev = mdev;
 
+	/*
+	 * Write-combining is required to expose BlueFlame (WC) UARs through the
+	 * dynamic MLX5_IB_OBJECT_UAR ioctl path.  The legacy static UAR path
+	 * already maps doorbell pages with pgprot_writecombine(), so advertise
+	 * WC support whenever the platform actually provides it.
+	 */
+#if defined(VM_MEMATTR_WRITE_COMBINING)
+	dev->wc_support = true;
+#endif
+
 	dev->port = kcalloc(MLX5_CAP_GEN(mdev, num_ports), sizeof(*dev->port),
 			    GFP_KERNEL);
 	if (!dev->port)