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Subject: Re: [PATCH v4 09/10] vfio/fsl-mc: Add read/write support for fsl-mc
 devices
To:     Diana Craciun <diana.craciun@oss.nxp.com>,
        alex.williamson@redhat.com, kvm@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, bharatb.linux@gmail.com,
        laurentiu.tudor@nxp.com, Bharat Bhushan <Bharat.Bhushan@nxp.com>
References: <20200826093315.5279-1-diana.craciun@oss.nxp.com>
 <20200826093315.5279-10-diana.craciun@oss.nxp.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <182a6686-a1ca-398b-2ccc-8a5638ffe7aa@redhat.com>
Date:   Fri, 4 Sep 2020 10:18:56 +0200
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Hi Diana,

On 8/26/20 11:33 AM, Diana Craciun wrote:
> The software uses a memory-mapped I/O command interface (MC portals) to
> communicate with the MC hardware. This command interface is used to
> discover, enumerate, configure and remove DPAA2 objects. The DPAA2
> objects use MSIs, so the command interface needs to be emulated
> such that the correct MSI is configured in the hardware (the guest
> has the virtual MSIs).
What I don't get is all the regions are mmappable too.
And this patch does not seem to introduce special handling with respect
to MSIs. Please could you clarify?
> 
> This patch is adding read/write support for fsl-mc devices. The mc
> commands are emulated by the userspace. The host is just passing
> the correct command to the hardware.
> 
> Also the current patch limits userspace to write complete
> 64byte command once and read 64byte response by one ioctl.
> 
> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@nxp.com>
> Signed-off-by: Diana Craciun <diana.craciun@oss.nxp.com>
> ---
>  drivers/vfio/fsl-mc/vfio_fsl_mc.c         | 115 +++++++++++++++++++++-
>  drivers/vfio/fsl-mc/vfio_fsl_mc_private.h |   1 +
>  2 files changed, 114 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> index 73834f488a94..27713aa86878 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> @@ -12,6 +12,7 @@
>  #include <linux/types.h>
>  #include <linux/vfio.h>
>  #include <linux/fsl/mc.h>
> +#include <linux/delay.h>
>  
>  #include "vfio_fsl_mc_private.h"
>  
> @@ -106,6 +107,9 @@ static int vfio_fsl_mc_regions_init(struct vfio_fsl_mc_device *vdev)
>  		vdev->regions[i].size = resource_size(res);
>  		vdev->regions[i].flags = VFIO_REGION_INFO_FLAG_MMAP;
>  		vdev->regions[i].type = mc_dev->regions[i].flags & IORESOURCE_BITS;
> +		vdev->regions[i].flags |= VFIO_REGION_INFO_FLAG_READ;
> +		if (!(mc_dev->regions[i].flags & IORESOURCE_READONLY))
> +			vdev->regions[i].flags |= VFIO_REGION_INFO_FLAG_WRITE;
>  	}
>  
>  	vdev->num_regions = mc_dev->obj_desc.region_count;
> @@ -114,6 +118,11 @@ static int vfio_fsl_mc_regions_init(struct vfio_fsl_mc_device *vdev)
>  
>  static void vfio_fsl_mc_regions_cleanup(struct vfio_fsl_mc_device *vdev)
>  {
> +	int i;
> +
> +	for (i = 0; i < vdev->num_regions; i++)
> +		iounmap(vdev->regions[i].ioaddr);
> +
>  	vdev->num_regions = 0;
>  	kfree(vdev->regions);
>  }
> @@ -311,13 +320,115 @@ static long vfio_fsl_mc_ioctl(void *device_data, unsigned int cmd,
>  static ssize_t vfio_fsl_mc_read(void *device_data, char __user *buf,
>  				size_t count, loff_t *ppos)
>  {
> -	return -EINVAL;
> +	struct vfio_fsl_mc_device *vdev = device_data;
> +	unsigned int index = VFIO_FSL_MC_OFFSET_TO_INDEX(*ppos);
> +	loff_t off = *ppos & VFIO_FSL_MC_OFFSET_MASK;
> +	struct vfio_fsl_mc_region *region;
> +	u64 data[8];
> +	int i;
> +
> +	if (index >= vdev->num_regions)
> +		return -EINVAL;
> +
> +	region = &vdev->regions[index];
> +
> +	if (!(region->flags & VFIO_REGION_INFO_FLAG_READ))
> +		return -EINVAL;
> +
> +	if (!region->ioaddr) {
> +		region->ioaddr = ioremap(region->addr, region->size);
> +		if (!region->ioaddr)
> +			return -ENOMEM;
> +	}
> +
> +	if (count != 64 || off != 0)
> +		return -EINVAL;
> +
> +	for (i = 7; i >= 0; i--)
> +		data[i] = readq(region->ioaddr + i * sizeof(uint64_t));
> +
> +	if (copy_to_user(buf, data, 64))
> +		return -EFAULT;
> +
> +	return count;
> +}
> +
> +#define MC_CMD_COMPLETION_TIMEOUT_MS    5000
> +#define MC_CMD_COMPLETION_POLLING_MAX_SLEEP_USECS    500
> +
> +static int vfio_fsl_mc_send_command(void __iomem *ioaddr, uint64_t *cmd_data)
> +{
> +	int i;
> +	enum mc_cmd_status status;
> +	unsigned long timeout_usecs = MC_CMD_COMPLETION_TIMEOUT_MS * 1000;
> +
> +	/* Write at command parameter into portal */
> +	for (i = 7; i >= 1; i--)
> +		writeq_relaxed(cmd_data[i], ioaddr + i * sizeof(uint64_t));
> +
> +	/* Write command header in the end */
> +	writeq(cmd_data[0], ioaddr);
> +
> +	/* Wait for response before returning to user-space
> +	 * This can be optimized in future to even prepare response
> +	 * before returning to user-space and avoid read ioctl.
> +	 */
> +	for (;;) {
> +		u64 header;
> +		struct mc_cmd_header *resp_hdr;
> +
> +		header = cpu_to_le64(readq_relaxed(ioaddr));
> +
> +		resp_hdr = (struct mc_cmd_header *)&header;
> +		status = (enum mc_cmd_status)resp_hdr->status;
> +		if (status != MC_CMD_STATUS_READY)
> +			break;
> +
> +		udelay(MC_CMD_COMPLETION_POLLING_MAX_SLEEP_USECS);
> +		timeout_usecs -= MC_CMD_COMPLETION_POLLING_MAX_SLEEP_USECS;
> +		if (timeout_usecs == 0)
> +			return -ETIMEDOUT;
> +	}
> +
> +	return 0;
>  }
>  
>  static ssize_t vfio_fsl_mc_write(void *device_data, const char __user *buf,
>  				 size_t count, loff_t *ppos)
>  {
> -	return -EINVAL;
> +	struct vfio_fsl_mc_device *vdev = device_data;
> +	unsigned int index = VFIO_FSL_MC_OFFSET_TO_INDEX(*ppos);
> +	loff_t off = *ppos & VFIO_FSL_MC_OFFSET_MASK;
> +	struct vfio_fsl_mc_region *region;
> +	u64 data[8];
> +	int ret;
> +
> +	if (index >= vdev->num_regions)
> +		return -EINVAL;
> +
> +	region = &vdev->regions[index];
> +
> +	if (!(region->flags & VFIO_REGION_INFO_FLAG_WRITE))
> +		return -EINVAL;
> +
> +	if (!region->ioaddr) {
> +		region->ioaddr = ioremap(region->addr, region->size);
> +		if (!region->ioaddr)
> +			return -ENOMEM;
> +	}
> +
> +	if (count != 64 || off != 0)
> +		return -EINVAL;
> +
> +	if (copy_from_user(&data, buf, 64))
> +		return -EFAULT;
> +
> +	ret = vfio_fsl_mc_send_command(region->ioaddr, data);
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +
>  }
>  
>  static int vfio_fsl_mc_mmap_mmio(struct vfio_fsl_mc_region region,
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h b/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
> index bbfca8b55f8a..e6804e516c4a 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
> @@ -32,6 +32,7 @@ struct vfio_fsl_mc_region {
>  	u32			type;
>  	u64			addr;
>  	resource_size_t		size;
> +	void __iomem		*ioaddr;
>  };
>  
>  struct vfio_fsl_mc_device {
> 
Thanks

Eric