Date:   Thu, 10 Sep 2020 10:20:00 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Diana Craciun OSS <diana.craciun@....nxp.com>,
        alex.williamson@...hat.com, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, bharatb.linux@...il.com,
        laurentiu.tudor@....com, Bharat Bhushan <Bharat.Bhushan@....com>
Subject: Re: [PATCH v4 09/10] vfio/fsl-mc: Add read/write support for fsl-mc
 devices

Hi Diana,

On 9/7/20 4:34 PM, Diana Craciun OSS wrote:
> Hi Eric,
> 
> On 9/4/2020 11:18 AM, Auger Eric wrote:
>> 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?
> 
> The device can be controlled using commands issued towards a firmware.
> Most of the commands can be passthrough, among exceptions is the command
> that configures the interrupts. In a guest the interrupts are emulated
> and for the hardware the numbers in the guest mean nothing. So, in a
> virtual machine scenario, the DPMCP and DPRC regions are emulated in
> qemu such that the command which configures the interrupts will not go
> to hardware with the information set by the guest.
> However there are other scenarios apart from virtual machines like DPDK
> in which the interrupt configuration command is not used. The problem
> might be that the userspace could issue the command because there is no
> restriction in the VFIO, but in that case the worst thing that may
> happen is for the interrupts for the device not to work.
> However it is possible to restrict the command for this scenario as well
> if I change the code and not allow the DPRC region to be mmapable. In
> practice it proved that it might not gain much by direct assigning that
> area. Also the interrupt configuration command was restricted from the
> firmware to be issued only from the DPRC device region to help such a
> scenario.
Yes actually I meant that the region used to configure MSIs should not
be mmappable then?


Thanks

Eric
> 
> 
>>>
>>> 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@....com>
>>> Signed-off-by: Diana Craciun <diana.craciun@....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
>>
> 
> Thanks,
> Diana
> 

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