Re: [PATCH V1 mlx5-next 11/13] vfio/mlx5: Implement vfio_pci driver for mlx5 devices

[Yishai Hadas <yishaih@nvidia.com>]

On 10/19/2021 12:59 PM, Shameerali Kolothum Thodi wrote:
>
>> -----Original Message-----
>> From: Yishai Hadas [mailto:yishaih@nvidia.com]
>> Sent: 13 October 2021 10:47
>> To: alex.williamson@redhat.com; bhelgaas@google.com; jgg@nvidia.com;
>> saeedm@nvidia.com
>> Cc: linux-pci@vger.kernel.org; kvm@vger.kernel.org; netdev@vger.kernel.org;
>> kuba@kernel.org; leonro@nvidia.com; kwankhede@nvidia.com;
>> mgurtovoy@nvidia.com; yishaih@nvidia.com; maorg@nvidia.com
>> Subject: [PATCH V1 mlx5-next 11/13] 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.
>>
>> Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
>> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
>> ---
>>   MAINTAINERS                    |   6 +
>>   drivers/vfio/pci/Kconfig       |   3 +
>>   drivers/vfio/pci/Makefile      |   2 +
>>   drivers/vfio/pci/mlx5/Kconfig  |  11 +
>>   drivers/vfio/pci/mlx5/Makefile |   4 +
>>   drivers/vfio/pci/mlx5/main.c   | 692 +++++++++++++++++++++++++++++++++
>>   6 files changed, 718 insertions(+)
>>   create mode 100644 drivers/vfio/pci/mlx5/Kconfig
>>   create mode 100644 drivers/vfio/pci/mlx5/Makefile
>>   create mode 100644 drivers/vfio/pci/mlx5/main.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index abdcbcfef73d..e824bfab4a01 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -19699,6 +19699,12 @@ 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
>> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
>> index 860424ccda1b..187b9c259944 100644
>> --- a/drivers/vfio/pci/Kconfig
>> +++ b/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
>> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
>> index 349d68d242b4..ed9d6f2e0555 100644
>> --- a/drivers/vfio/pci/Makefile
>> +++ b/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/
>> diff --git a/drivers/vfio/pci/mlx5/Kconfig b/drivers/vfio/pci/mlx5/Kconfig
>> new file mode 100644
>> index 000000000000..a3ce00add4fe
>> --- /dev/null
>> +++ b/drivers/vfio/pci/mlx5/Kconfig
>> @@ -0,0 +1,11 @@
>> +# SPDX-License-Identifier: GPL-2.0-only
>> +config MLX5_VFIO_PCI
>> +	tristate "VFIO support for MLX5 PCI devices"
>> +	depends on MLX5_CORE
>> +	select VFIO_PCI_CORE
>> +	help
>> +	  This provides a PCI support for MLX5 devices using the VFIO
>> +	  framework. The device specific driver supports suspend/resume
>> +	  of the MLX5 device.
>> +
>> +	  If you don't know what to do here, say N.
>> diff --git a/drivers/vfio/pci/mlx5/Makefile b/drivers/vfio/pci/mlx5/Makefile
>> new file mode 100644
>> index 000000000000..689627da7ff5
>> --- /dev/null
>> +++ b/drivers/vfio/pci/mlx5/Makefile
>> @@ -0,0 +1,4 @@
>> +# SPDX-License-Identifier: GPL-2.0-only
>> +obj-$(CONFIG_MLX5_VFIO_PCI) += mlx5-vfio-pci.o
>> +mlx5-vfio-pci-y := main.o cmd.o
>> +
>> diff --git a/drivers/vfio/pci/mlx5/main.c b/drivers/vfio/pci/mlx5/main.c
>> new file mode 100644
>> index 000000000000..e36302b444a6
>> --- /dev/null
>> +++ b/drivers/vfio/pci/mlx5/main.c
>> @@ -0,0 +1,692 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved
>> + */
>> +
>> +#include <linux/device.h>
>> +#include <linux/eventfd.h>
>> +#include <linux/file.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/iommu.h>
>> +#include <linux/module.h>
>> +#include <linux/mutex.h>
>> +#include <linux/notifier.h>
>> +#include <linux/pci.h>
>> +#include <linux/pm_runtime.h>
>> +#include <linux/types.h>
>> +#include <linux/uaccess.h>
>> +#include <linux/vfio.h>
>> +#include <linux/sched/mm.h>
>> +#include <linux/vfio_pci_core.h>
>> +
>> +#include "cmd.h"
>> +
>> +enum {
>> +	MLX5VF_PCI_FREEZED = 1 << 0,
>> +};
>> +
>> +enum {
>> +	MLX5VF_REGION_PENDING_BYTES = 1 << 0,
>> +	MLX5VF_REGION_DATA_SIZE = 1 << 1,
>> +};
>> +
>> +#define MLX5VF_MIG_REGION_DATA_SIZE SZ_128K
>> +/* Data section offset from migration region */
>> +#define MLX5VF_MIG_REGION_DATA_OFFSET
>> \
>> +	(sizeof(struct vfio_device_migration_info))
>> +
>> +#define VFIO_DEVICE_MIGRATION_OFFSET(x)
>> \
>> +	(offsetof(struct vfio_device_migration_info, x))
>> +
>> +struct mlx5vf_pci_migration_info {
>> +	u32 vfio_dev_state; /* VFIO_DEVICE_STATE_XXX */
>> +	u32 dev_state; /* device migration state */
>> +	u32 region_state; /* Use MLX5VF_REGION_XXX */
>> +	u16 vhca_id;
>> +	struct mlx5_vhca_state_data vhca_state_data;
>> +};
>> +
>> +struct mlx5vf_pci_core_device {
>> +	struct vfio_pci_core_device core_device;
>> +	u8 migrate_cap:1;
>> +	/* protect migartion state */
>> +	struct mutex state_mutex;
>> +	struct mlx5vf_pci_migration_info vmig;
>> +};
>> +
>> +static int mlx5vf_pci_unquiesce_device(struct mlx5vf_pci_core_device
>> *mvdev)
>> +{
>> +	return mlx5vf_cmd_resume_vhca(mvdev->core_device.pdev,
>> +				      mvdev->vmig.vhca_id,
>> +
>> MLX5_RESUME_VHCA_IN_OP_MOD_RESUME_MASTER);
>> +}
>> +
>> +static int mlx5vf_pci_quiesce_device(struct mlx5vf_pci_core_device *mvdev)
>> +{
>> +	return mlx5vf_cmd_suspend_vhca(
>> +		mvdev->core_device.pdev, mvdev->vmig.vhca_id,
>> +		MLX5_SUSPEND_VHCA_IN_OP_MOD_SUSPEND_MASTER);
>> +}
>> +
>> +static int mlx5vf_pci_unfreeze_device(struct mlx5vf_pci_core_device
>> *mvdev)
>> +{
>> +	int ret;
>> +
>> +	ret = mlx5vf_cmd_resume_vhca(mvdev->core_device.pdev,
>> +				     mvdev->vmig.vhca_id,
>> +
>> MLX5_RESUME_VHCA_IN_OP_MOD_RESUME_SLAVE);
>> +	if (ret)
>> +		return ret;
>> +
>> +	mvdev->vmig.dev_state &= ~MLX5VF_PCI_FREEZED;
>> +	return 0;
>> +}
>> +
>> +static int mlx5vf_pci_freeze_device(struct mlx5vf_pci_core_device *mvdev)
>> +{
>> +	int ret;
>> +
>> +	ret = mlx5vf_cmd_suspend_vhca(
>> +		mvdev->core_device.pdev, mvdev->vmig.vhca_id,
>> +		MLX5_SUSPEND_VHCA_IN_OP_MOD_SUSPEND_SLAVE);
>> +	if (ret)
>> +		return ret;
>> +
>> +	mvdev->vmig.dev_state |= MLX5VF_PCI_FREEZED;
>> +	return 0;
>> +}
>> +
>> +static int mlx5vf_pci_save_device_data(struct mlx5vf_pci_core_device
>> *mvdev)
>> +{
>> +	u32 state_size = 0;
>> +	int ret;
>> +
>> +	if (!(mvdev->vmig.dev_state & MLX5VF_PCI_FREEZED))
>> +		return -EFAULT;
>> +
>> +	/* If we already read state no reason to re-read */
>> +	if (mvdev->vmig.vhca_state_data.state_size)
>> +		return 0;
>> +
>> +	ret = mlx5vf_cmd_query_vhca_migration_state(
>> +		mvdev->core_device.pdev, mvdev->vmig.vhca_id, &state_size);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return mlx5vf_cmd_save_vhca_state(mvdev->core_device.pdev,
>> +					  mvdev->vmig.vhca_id, state_size,
>> +					  &mvdev->vmig.vhca_state_data);
>> +}
>> +
>> +static int mlx5vf_pci_new_write_window(struct mlx5vf_pci_core_device
>> *mvdev)
>> +{
>> +	struct mlx5_vhca_state_data *state_data =
>> &mvdev->vmig.vhca_state_data;
>> +	u32 num_pages_needed;
>> +	u64 allocated_ready;
>> +	u32 bytes_needed;
>> +
>> +	/* Check how many bytes are available from previous flows */
>> +	WARN_ON(state_data->num_pages * PAGE_SIZE <
>> +		state_data->win_start_offset);
>> +	allocated_ready = (state_data->num_pages * PAGE_SIZE) -
>> +			  state_data->win_start_offset;
>> +	WARN_ON(allocated_ready > MLX5VF_MIG_REGION_DATA_SIZE);
>> +
>> +	bytes_needed = MLX5VF_MIG_REGION_DATA_SIZE - allocated_ready;
>> +	if (!bytes_needed)
>> +		return 0;
>> +
>> +	num_pages_needed = DIV_ROUND_UP_ULL(bytes_needed, PAGE_SIZE);
>> +	return mlx5vf_add_migration_pages(state_data, num_pages_needed);
>> +}
>> +
>> +static ssize_t
>> +mlx5vf_pci_handle_migration_data_size(struct mlx5vf_pci_core_device
>> *mvdev,
>> +				      char __user *buf, bool iswrite)
>> +{
>> +	struct mlx5vf_pci_migration_info *vmig = &mvdev->vmig;
>> +	u64 data_size;
>> +	int ret;
>> +
>> +	if (iswrite) {
>> +		/* data_size is writable only during resuming state */
>> +		if (vmig->vfio_dev_state != VFIO_DEVICE_STATE_RESUMING)
>> +			return -EINVAL;
>> +
>> +		ret = copy_from_user(&data_size, buf, sizeof(data_size));
>> +		if (ret)
>> +			return -EFAULT;
>> +
>> +		vmig->vhca_state_data.state_size += data_size;
>> +		vmig->vhca_state_data.win_start_offset += data_size;
>> +		ret = mlx5vf_pci_new_write_window(mvdev);
>> +		if (ret)
>> +			return ret;
>> +
>> +	} else {
>> +		if (vmig->vfio_dev_state != VFIO_DEVICE_STATE_SAVING)
>> +			return -EINVAL;
>> +
>> +		data_size = min_t(u64, MLX5VF_MIG_REGION_DATA_SIZE,
>> +				  vmig->vhca_state_data.state_size -
>> +				  vmig->vhca_state_data.win_start_offset);
>> +		ret = copy_to_user(buf, &data_size, sizeof(data_size));
>> +		if (ret)
>> +			return -EFAULT;
>> +	}
>> +
>> +	vmig->region_state |= MLX5VF_REGION_DATA_SIZE;
>> +	return sizeof(data_size);
>> +}
>> +
>> +static ssize_t
>> +mlx5vf_pci_handle_migration_data_offset(struct mlx5vf_pci_core_device
>> *mvdev,
>> +					char __user *buf, bool iswrite)
>> +{
>> +	static const u64 data_offset = MLX5VF_MIG_REGION_DATA_OFFSET;
>> +	int ret;
>> +
>> +	/* RO field */
>> +	if (iswrite)
>> +		return -EFAULT;
>> +
>> +	ret = copy_to_user(buf, &data_offset, sizeof(data_offset));
>> +	if (ret)
>> +		return -EFAULT;
>> +
>> +	return sizeof(data_offset);
>> +}
>> +
>> +static ssize_t
>> +mlx5vf_pci_handle_migration_pending_bytes(struct mlx5vf_pci_core_device
>> *mvdev,
>> +					  char __user *buf, bool iswrite)
>> +{
>> +	struct mlx5vf_pci_migration_info *vmig = &mvdev->vmig;
>> +	u64 pending_bytes;
>> +	int ret;
>> +
>> +	/* RO field */
>> +	if (iswrite)
>> +		return -EFAULT;
>> +
>> +	if (vmig->vfio_dev_state == (VFIO_DEVICE_STATE_SAVING |
>> +				     VFIO_DEVICE_STATE_RUNNING)) {
>> +		/* In pre-copy state we have no data to return for now,
>> +		 * return 0 pending bytes
>> +		 */
>> +		pending_bytes = 0;
>> +	} else {
>> +		if (!vmig->vhca_state_data.state_size)
>> +			return 0;
>> +		pending_bytes = vmig->vhca_state_data.state_size -
>> +				vmig->vhca_state_data.win_start_offset;
>> +	}
>> +
>> +	ret = copy_to_user(buf, &pending_bytes, sizeof(pending_bytes));
>> +	if (ret)
>> +		return -EFAULT;
>> +
>> +	/* Window moves forward once data from previous iteration was read */
>> +	if (vmig->region_state & MLX5VF_REGION_DATA_SIZE)
>> +		vmig->vhca_state_data.win_start_offset +=
>> +			min_t(u64, MLX5VF_MIG_REGION_DATA_SIZE, pending_bytes);
>> +
>> +	WARN_ON(vmig->vhca_state_data.win_start_offset >
>> +		vmig->vhca_state_data.state_size);
>> +
>> +	/* New iteration started */
>> +	vmig->region_state = MLX5VF_REGION_PENDING_BYTES;
>> +	return sizeof(pending_bytes);
>> +}
>> +
>> +static int mlx5vf_load_state(struct mlx5vf_pci_core_device *mvdev)
>> +{
>> +	if (!mvdev->vmig.vhca_state_data.state_size)
>> +		return 0;
>> +
>> +	return mlx5vf_cmd_load_vhca_state(mvdev->core_device.pdev,
>> +					  mvdev->vmig.vhca_id,
>> +					  &mvdev->vmig.vhca_state_data);
>> +}
>> +
>> +static void mlx5vf_reset_mig_state(struct mlx5vf_pci_core_device *mvdev)
>> +{
>> +	struct mlx5vf_pci_migration_info *vmig = &mvdev->vmig;
>> +
>> +	vmig->region_state = 0;
>> +	mlx5vf_reset_vhca_state(&vmig->vhca_state_data);
>> +}
>> +
>> +static int mlx5vf_pci_set_device_state(struct mlx5vf_pci_core_device
>> *mvdev,
>> +				       u32 state)
>> +{
>> +	struct mlx5vf_pci_migration_info *vmig = &mvdev->vmig;
>> +	u32 old_state = vmig->vfio_dev_state;
>> +	int ret = 0;
>> +
>> +	if (vfio_is_state_invalid(state) || vfio_is_state_invalid(old_state))
>> +		return -EINVAL;
>> +
>> +	/* Running switches off */
>> +	if ((old_state & VFIO_DEVICE_STATE_RUNNING) !=
>> +	    (state & VFIO_DEVICE_STATE_RUNNING) &&
>> +	    (old_state & VFIO_DEVICE_STATE_RUNNING)) {
>> +		ret = mlx5vf_pci_quiesce_device(mvdev);
>> +		if (ret)
>> +			return ret;
>> +		ret = mlx5vf_pci_freeze_device(mvdev);
>> +		if (ret) {
>> +			vmig->vfio_dev_state = VFIO_DEVICE_STATE_INVALID;
>> +			return ret;
>> +		}
>> +	}
>> +
>> +	/* Resuming switches off */
>> +	if ((old_state & VFIO_DEVICE_STATE_RESUMING) !=
>> +	    (state & VFIO_DEVICE_STATE_RESUMING) &&
>> +	    (old_state & VFIO_DEVICE_STATE_RESUMING)) {
>> +		/* deserialize state into the device */
>> +		ret = mlx5vf_load_state(mvdev);
>> +		if (ret) {
>> +			vmig->vfio_dev_state = VFIO_DEVICE_STATE_INVALID;
>> +			return ret;
>> +		}
>> +	}
>> +
>> +	/* Resuming switches on */
>> +	if ((old_state & VFIO_DEVICE_STATE_RESUMING) !=
>> +	    (state & VFIO_DEVICE_STATE_RESUMING) &&
>> +	    (state & VFIO_DEVICE_STATE_RESUMING)) {
>> +		mlx5vf_reset_mig_state(mvdev);
>> +		ret = mlx5vf_pci_new_write_window(mvdev);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	/* Saving switches on */
>> +	if ((old_state & VFIO_DEVICE_STATE_SAVING) !=
>> +	    (state & VFIO_DEVICE_STATE_SAVING) &&
>> +	    (state & VFIO_DEVICE_STATE_SAVING)) {
>> +		if (!(state & VFIO_DEVICE_STATE_RUNNING)) {
>> +			/* serialize post copy */
>> +			ret = mlx5vf_pci_save_device_data(mvdev);
> Does it actually get into post-copy here? The pre-copy state(old_state)
> has the _SAVING bit set already and post-copy state( new state) also
> has _SAVING set. It looks like we need to handle the post copy in the above
> "Running switches off" and check for (state & _SAVING).
>
> Or Am I missing something?
>

The above checks for a change in the SAVING bit, if it was turned on and 
we are not RUNNING it means post copy.

Turning on SAVING when we are RUNNING will end-up with returning zero 
bytes upon pending bytes as we don't support for now dirty pages.

see mlx5vf_pci_handle_migration_pending_bytes().

Yishai