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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.12.13 at 14:55, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> On 03/12/13 13:44, Jan Beulich wrote:
>> For multi-byte operations all affected ports' bits in the bitmap need
>> to be checked, not just the first port's one.
>>
>> Reported-by: Matthew Daley <mattd@xxxxxxxxxxx>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>> --- a/xen/arch/x86/hvm/vmx/vvmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
>> @@ -2134,7 +2134,6 @@ int nvmx_n2_vmexit_handler(struct cpu_us
>>      struct nestedvcpu *nvcpu = &vcpu_nestedhvm(v);
>>      struct nestedvmx *nvmx = &vcpu_2_nvmx(v);
>>      u32 ctrl;
>> -    u8 *bitmap;
>>  
>>      nvcpu->nv_vmexit_pending = 0;
>>      nvmx->intr.intr_info = 0;
>> @@ -2220,15 +2219,22 @@ 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;
>> +            for ( port = qual >> 16, size = (qual & 7) + 1; ; )
>> +            {
>> +                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;
>> +            } while ( !nvcpu->nv_vmexit_pending );
> 
> You have a rather odd looking "for () { } while ()" loop, which appears
> to be a while loop with no body and a constant loop condition.  Is this
> intended?

Oops, no, of course not.

Jan


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