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Subject: Re: [PATCH v10 04/11] vfio/pci: Add VFIO_REGION_TYPE_NESTED region
 type
To:     Zenghui Yu <yuzenghui@huawei.com>, eric.auger.pro@gmail.com,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, joro@8bytes.org,
        alex.williamson@redhat.com, jacob.jun.pan@linux.intel.com,
        yi.l.liu@intel.com, robin.murphy@arm.com
References: <20200320161911.27494-1-eric.auger@redhat.com>
 <20200320161911.27494-5-eric.auger@redhat.com>
 <d21e74e5-00a7-79f9-24d2-c9385409cc05@huawei.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <ce21ef1e-5ffd-586c-0925-d3a59eb0c30d@redhat.com>
Date:   Fri, 13 Nov 2020 17:12:14 +0100
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Hi Zenghui,
On 9/24/20 10:23 AM, Zenghui Yu wrote:
> Hi Eric,
> 
> On 2020/3/21 0:19, Eric Auger wrote:
>> Add a new specific DMA_FAULT region aiming to exposed nested mode
>> translation faults.
>>
>> The region has a ring buffer that contains the actual fault
>> records plus a header allowing to handle it (tail/head indices,
>> max capacity, entry size). At the moment the region is dimensionned
>> for 512 fault records.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> [...]
> 
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index 379a02c36e37..586b89debed5 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -260,6 +260,69 @@ int vfio_pci_set_power_state(struct
>> vfio_pci_device *vdev, pci_power_t state)
>>       return ret;
>>   }
>>   +static void vfio_pci_dma_fault_release(struct vfio_pci_device *vdev,
>> +                       struct vfio_pci_region *region)
>> +{
>> +}
>> +
>> +static int vfio_pci_dma_fault_add_capability(struct vfio_pci_device
>> *vdev,
>> +                         struct vfio_pci_region *region,
>> +                         struct vfio_info_cap *caps)
>> +{
>> +    struct vfio_region_info_cap_fault cap = {
>> +        .header.id = VFIO_REGION_INFO_CAP_DMA_FAULT,
>> +        .header.version = 1,
>> +        .version = 1,
>> +    };
>> +    return vfio_info_add_capability(caps, &cap.header, sizeof(cap));
>> +}
>> +
>> +static const struct vfio_pci_regops vfio_pci_dma_fault_regops = {
>> +    .rw        = vfio_pci_dma_fault_rw,
>> +    .release    = vfio_pci_dma_fault_release,
>> +    .add_capability = vfio_pci_dma_fault_add_capability,
>> +};
>> +
>> +#define DMA_FAULT_RING_LENGTH 512
>> +
>> +static int vfio_pci_init_dma_fault_region(struct vfio_pci_device *vdev)
>> +{
>> +    struct vfio_region_dma_fault *header;
>> +    size_t size;
>> +    int ret;
>> +
>> +    mutex_init(&vdev->fault_queue_lock);
>> +
>> +    /*
>> +     * We provision 1 page for the header and space for
>> +     * DMA_FAULT_RING_LENGTH fault records in the ring buffer.
>> +     */
>> +    size = ALIGN(sizeof(struct iommu_fault) *
>> +             DMA_FAULT_RING_LENGTH, PAGE_SIZE) + PAGE_SIZE;
>> +
>> +    vdev->fault_pages = kzalloc(size, GFP_KERNEL);
>> +    if (!vdev->fault_pages)
>> +        return -ENOMEM;
>> +
>> +    ret = vfio_pci_register_dev_region(vdev,
>> +        VFIO_REGION_TYPE_NESTED,
>> +        VFIO_REGION_SUBTYPE_NESTED_DMA_FAULT,
>> +        &vfio_pci_dma_fault_regops, size,
>> +        VFIO_REGION_INFO_FLAG_READ | VFIO_REGION_INFO_FLAG_WRITE,
>> +        vdev->fault_pages);
>> +    if (ret)
>> +        goto out;
>> +
>> +    header = (struct vfio_region_dma_fault *)vdev->fault_pages;
>> +    header->entry_size = sizeof(struct iommu_fault);
>> +    header->nb_entries = DMA_FAULT_RING_LENGTH;
>> +    header->offset = sizeof(struct vfio_region_dma_fault);
>> +    return 0;
>> +out:
>> +    kfree(vdev->fault_pages);
>> +    return ret;
>> +}
>> +
>>   static int vfio_pci_enable(struct vfio_pci_device *vdev)
>>   {
>>       struct pci_dev *pdev = vdev->pdev;
>> @@ -358,6 +421,10 @@ static int vfio_pci_enable(struct vfio_pci_device
>> *vdev)
>>           }
>>       }
>>   +    ret = vfio_pci_init_dma_fault_region(vdev);
>> +    if (ret)
>> +        goto disable_exit;
>> +
>>       vfio_pci_probe_mmaps(vdev);
>>         return 0;
>> @@ -1383,6 +1450,7 @@ static void vfio_pci_remove(struct pci_dev *pdev)
>>         vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
>>       kfree(vdev->region);
>> +    kfree(vdev->fault_pages);
>>       mutex_destroy(&vdev->ioeventfds_lock);
>>         if (!disable_idle_d3)
>> diff --git a/drivers/vfio/pci/vfio_pci_private.h
>> b/drivers/vfio/pci/vfio_pci_private.h
>> index 8a2c7607d513..a392f50e3a99 100644
>> --- a/drivers/vfio/pci/vfio_pci_private.h
>> +++ b/drivers/vfio/pci/vfio_pci_private.h
>> @@ -119,6 +119,8 @@ struct vfio_pci_device {
>>       int            ioeventfds_nr;
>>       struct eventfd_ctx    *err_trigger;
>>       struct eventfd_ctx    *req_trigger;
>> +    u8            *fault_pages;
> 
> What's the reason to use 'u8'? It doesn't match the type of header, nor
> the type of ring buffer.
actually it matches
	u8                      *pci_config_map;
        u8                      *vconfig;

fault_pages is the va of the ring buffer. In the header, offset is the
offset of the ring wrt start of the region.

> 
>> +    struct mutex        fault_queue_lock;
>>       struct list_head    dummy_resources_list;
>>       struct mutex        ioeventfds_lock;
>>       struct list_head    ioeventfds_list;
>> @@ -150,6 +152,14 @@ extern ssize_t vfio_pci_vga_rw(struct
>> vfio_pci_device *vdev, char __user *buf,
>>   extern long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t
>> offset,
>>                      uint64_t data, int count, int fd);
>>   +struct vfio_pci_fault_abi {
>> +    u32 entry_size;
>> +};
> 
> This is not used by this patch (and the whole series).
removed
> 
>> +
>> +extern size_t vfio_pci_dma_fault_rw(struct vfio_pci_device *vdev,
>> +                    char __user *buf, size_t count,
>> +                    loff_t *ppos, bool iswrite);
>> +
>>   extern int vfio_pci_init_perm_bits(void);
>>   extern void vfio_pci_uninit_perm_bits(void);
>>   diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c
>> b/drivers/vfio/pci/vfio_pci_rdwr.c
>> index a87992892a9f..4004ab8cad0e 100644
>> --- a/drivers/vfio/pci/vfio_pci_rdwr.c
>> +++ b/drivers/vfio/pci/vfio_pci_rdwr.c
>> @@ -274,6 +274,51 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device
>> *vdev, char __user *buf,
>>       return done;
>>   }
>>   +size_t vfio_pci_dma_fault_rw(struct vfio_pci_device *vdev, char
>> __user *buf,
>> +                 size_t count, loff_t *ppos, bool iswrite)
>> +{
>> +    unsigned int i = VFIO_PCI_OFFSET_TO_INDEX(*ppos) -
>> VFIO_PCI_NUM_REGIONS;
>> +    loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
>> +    void *base = vdev->region[i].data;
>> +    int ret = -EFAULT;
>> +
>> +    if (pos >= vdev->region[i].size)
>> +        return -EINVAL;
>> +
>> +    count = min(count, (size_t)(vdev->region[i].size - pos));
>> +
>> +    mutex_lock(&vdev->fault_queue_lock);
>> +
>> +    if (iswrite) {
>> +        struct vfio_region_dma_fault *header =
>> +            (struct vfio_region_dma_fault *)base;
>> +        u32 new_tail;
>> +
>> +        if (pos != 0 || count != 4) {
>> +            ret = -EINVAL;
>> +            goto unlock;
>> +        }
>> +
>> +        if (copy_from_user((void *)&new_tail, buf, count))
>> +            goto unlock;
>> +
>> +        if (new_tail > header->nb_entries) {
> 
> Maybe
> 
> new_tail >= header->nb_entries ?
sure

Thanks

Eric
> 
>> +            ret = -EINVAL;
>> +            goto unlock;
>> +        }
>> +        header->tail = new_tail;
>> +    } else {
>> +        if (copy_to_user(buf, base + pos, count))
>> +            goto unlock;
>> +    }
>> +    *ppos += count;
>> +    ret = count;
>> +unlock:
>> +    mutex_unlock(&vdev->fault_queue_lock);
>> +    return ret;
>> +}
>> +
>> +
>>   static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
>>   {
>>       struct vfio_pci_ioeventfd *ioeventfd = opaque;
> 
> 
> Thanks,
> Zenghui
>