Re: [Qemu-devel] [PATCH V7 6/6] Adding VMXNET3 device implementation

[Stefan Hajnoczi]

On Fri, Nov 16, 2012 at 2:55 PM, Dmitry Fleytman <address@hidden> wrote:
> +        /* Whether MSI-X support was installed successfully */
> +        uint8_t msix_used;
> +        /* Whether MSI support was installed successfully */
> +        uint8_t msi_used;

These two fields should be bool.

> +        /* Whether automatic interrupts masking enabled */
> +        uint8_t auto_int_masking;

bool

> +static inline void vmxnet3_flush_shmem_changes(void)
> +{
> +    /*
> +     * Flush shared memory changes
> +     * Needed before sending interrupt to guest to ensure
> +     * it gets consistent memory state
> +     */
> +    smp_wmb();
> +}

It's useful to document why a memory barrier is being used in each
instance.  Therefore hiding smp_wmb() inside a wrapper function isn't
great.

Also, it's suspicious that smb_wmb() is used but no other barriers are
used.  What about a read memory barrier when accessing shared memory
written by the guest?