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SubjectRe: [PATCH net-next 8/8] vhost: event suppression for packed ring
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On 2018年07月04日 12:13, Wei Xu wrote:
> On Tue, Jul 03, 2018 at 01:38:04PM +0800, Jason Wang wrote:
>> This patch introduces support for event suppression. This is done by
>> have a two areas: device area and driver area. One side could then try
>> to disable or enable (delayed) notification from other side by using a
>> boolean hint or event index interface in the areas.
>>
>> For more information, please refer Virtio spec.
>>
>> Signed-off-by: Jason Wang<jasowang@redhat.com>
>> ---
>> drivers/vhost/vhost.c | 191 ++++++++++++++++++++++++++++++++++++++++++++++----
>> drivers/vhost/vhost.h | 10 ++-
>> 2 files changed, 185 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> index 0f3f07c..cccbc82 100644
>> --- a/drivers/vhost/vhost.c
>> +++ b/drivers/vhost/vhost.c
>> @@ -1115,10 +1115,15 @@ static int vq_access_ok_packed(struct vhost_virtqueue *vq, unsigned int num,
>> struct vring_used __user *used)
>> {
>> struct vring_desc_packed *packed = (struct vring_desc_packed *)desc;
>> + struct vring_packed_desc_event *driver_event =
>> + (struct vring_packed_desc_event *)avail;
>> + struct vring_packed_desc_event *device_event =
>> + (struct vring_packed_desc_event *)used;
>>
>> - /* TODO: check device area and driver area */
>> return access_ok(VERIFY_READ, packed, num * sizeof(*packed)) &&
>> - access_ok(VERIFY_WRITE, packed, num * sizeof(*packed));
>> + access_ok(VERIFY_WRITE, packed, num * sizeof(*packed)) &&
> R/W parameter doesn't make sense to most architectures and the comment in x86
> says WRITE is a superset of READ, is it possible to converge them here?
>
> /**
> * access_ok: - Checks if a user space pointer is valid
> * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE. Note that
> * %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
> * to write to a block, it is always safe to read from it.
> * @addr: User space pointer to start of block to check
> * @size: Size of block to check
> *
> * Context: User context only. This function may sleep if pagefaults are
> * enabled.
> *
> * Checks if a pointer to a block of memory in user space is valid.
> *
> * Returns true (nonzero) if the memory block may be valid, false (zero)
> * if it is definitely invalid.
> *
> * Note that, depending on architecture, this function probably just
> * checks that the pointer is in the user space range - after calling
> * this function, memory access functions may still return -EFAULT.
> */
> #define access_ok(type, addr, size)
> ......
>
> Thanks,
> Wei
>

Well, this is a question that beyond the scope of this patch.

My understanding is we should keep it unless type was meaningless on all
archs.

Thanks

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