Re: [Xen-devel] [PATCH v2] nested VMX: fix I/O port exit emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.12.13 at 02:51, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx> wrote:
> Jan Beulich wrote on 2013-12-03:
>> @@ -2220,15 +2219,23 @@ int nvmx_n2_vmexit_handler(struct cpu_us
>>          if ( ctrl & CPU_BASED_ACTIVATE_IO_BITMAP )
>>          {
>>              unsigned long qual;
>> -            u16 port;
>> +            u16 port, size;
>> 
>>              __vmread(EXIT_QUALIFICATION, &qual);
>>              port = qual >> 16;
>> -            bitmap = nvmx->iobitmap[port >> 15];
>> -            if ( bitmap[(port & 0x7fff) >> 3] & (1 << (port & 0x7)) )
>> -                nvcpu->nv_vmexit_pending = 1;
>> +            size = (qual & 7) + 1;
>> +            do {
>> +                const u8 *bitmap = nvmx->iobitmap[port >> 15];
>> +
>> +                if ( bitmap[(port & 0x7fff) >> 3] & (1 << (port & 7)) )
>> +                    nvcpu->nv_vmexit_pending = 1;
>> +                if ( !--size )
>> +                    break;
>> +                if ( !++port )
>> +                    nvcpu->nv_vmexit_pending = 1;
> 
> If port overflow, will it cause vmexit or maybe other fault like GP or just 
> be ignored?

The documentation is explicit here: It causes a VM exit. And hence
the emulation is doing so too.

> Also, you need to check the DF bit to know the string direction 
> before updating the port.

I think Andrew already sufficiently clarified that part.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel