vfio/mlx5: Implement vfio_pci driver for mlx5 devices

This patch adds support for vfio_pci driver for mlx5 devices.

It uses vfio_pci_core to register to the VFIO subsystem and then
implements the mlx5 specific logic in the migration area.

The migration implementation follows the definition from uapi/vfio.h and
uses the mlx5 VF->PF command channel to achieve it.

This patch implements the suspend/resume flows.

Link: https://lore.kernel.org/all/20220224142024.147653-14-yishaih@nvidia.comReviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>

MAINTAINERS

@@ -20320,6 +20320,12 @@ L:	kvm@vger.kernel.org
 S:	Maintained
 F:	drivers/vfio/platform/
 
+VFIO MLX5 PCI DRIVER
+M:	Yishai Hadas <yishaih@nvidia.com>
+L:	kvm@vger.kernel.org
+S:	Maintained
+F:	drivers/vfio/pci/mlx5/
+
 VGA_SWITCHEROO
 R:	Lukas Wunner <lukas@wunner.de>
 S:	Maintained

drivers/vfio/pci/Kconfig

@@ -43,4 +43,7 @@ config VFIO_PCI_IGD
 
 	  To enable Intel IGD assignment through vfio-pci, say Y.
 endif
+
+source "drivers/vfio/pci/mlx5/Kconfig"
+
 endif

drivers/vfio/pci/Makefile

@@ -7,3 +7,5 @@ obj-$(CONFIG_VFIO_PCI_CORE) += vfio-pci-core.o
 vfio-pci-y := vfio_pci.o
 vfio-pci-$(CONFIG_VFIO_PCI_IGD) += vfio_pci_igd.o
 obj-$(CONFIG_VFIO_PCI) += vfio-pci.o
+
+obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/

drivers/vfio/pci/mlx5/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+config MLX5_VFIO_PCI
+	tristate "VFIO support for MLX5 PCI devices"
+	depends on MLX5_CORE
+	depends on VFIO_PCI_CORE
+	help
+	  This provides migration support for MLX5 devices using the VFIO
+	  framework.
+
+	  If you don't know what to do here, say N.

drivers/vfio/pci/mlx5/Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_MLX5_VFIO_PCI) += mlx5-vfio-pci.o
+mlx5-vfio-pci-y := main.o cmd.o
+

drivers/vfio/pci/mlx5/cmd.h

@@ -12,6 +12,7 @@
 struct mlx5_vf_migration_file {
 	struct file *filp;
 	struct mutex lock;
+	bool disabled;
 
 	struct sg_append_table table;
 	size_t total_length;