Re: [Xen-devel] [PATCH v7 15/15] x86/hvm: track large memory mapped accesses by buffer offset

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.07.15 at 15:10, <paul.durrant@xxxxxxxxxx> wrote:
> @@ -635,13 +605,49 @@ static int hvmemul_phys_mmio_access(
>      return rc;
>  }
>  
> +/*
> + * Multi-cycle MMIO handling is based upon the assumption that emulation
> + * of the same instruction will not access the same MMIO region more
> + * than once. Hence we can deal with re-emulation (for secondary or
> + * subsequent cycles) by looking up the result or previous I/O in a
> + * cache indexed by linear MMIO address.
> + */
> +static struct hvm_mmio_cache *hvmemul_find_mmio_cache(
> +    struct hvm_vcpu_io *vio, unsigned long gla, uint8_t dir)
> +{
> +    unsigned int i;
> +    struct hvm_mmio_cache *cache;
> +
> +    for ( i = 0; i < vio->mmio_cache_count; i ++ )
> +    {
> +        cache = &vio->mmio_cache[i];
> +
> +        if ( gla == cache->gla &&
> +             dir == cache->dir )
> +            return cache;
> +    }
> +
> +    i = vio->mmio_cache_count++;
> +    if( i == ARRAY_SIZE(vio->mmio_cache) )
> +        domain_crash(current->domain);

But you mustn't continue here, or at least force i into range so you
don't corrupt other data.

And while doing that please also add the missing space on the
if() line.

Jan


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