Re: [Xen-devel] [PATCH v2] x86/HVM: correct hvmemul_map_linear_addr() for multi-page case

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.09.18 at 13:06, <Paul.Durrant@xxxxxxxxxx> wrote:
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 13 September 2018 11:13
>> 
>> @@ -544,7 +574,7 @@ static void *hvmemul_map_linear_addr(
>>      struct hvm_emulate_ctxt *hvmemul_ctxt)
>>  {
>>      struct vcpu *curr = current;
>> -    void *err, *mapping;
>> +    void *err = ZERO_BLOCK_PTR, *mapping;
> 
> Given the revised logic, can't you just start *err with the value 
> ERR_PTR(~X86EMUL_OKAY) now? You can then lose the extra test in the first if 
> of update_map_err().

No, I don't think I can, because of ...

>>      unsigned int nr_frames = ((linear + bytes - !!bytes) >> PAGE_SHIFT) -
>>          (linear >> PAGE_SHIFT) + 1;
>>      unsigned int i;
>> @@ -600,27 +630,28 @@ static void *hvmemul_map_linear_addr(
>>              goto out;
>> 
>>          case HVMTRANS_bad_gfn_to_mfn:
>> -            err = NULL;
>> -            goto out;
>> +            err = update_map_err(err, NULL);
>> +            continue;
>> 
>>          case HVMTRANS_gfn_paged_out:
>>          case HVMTRANS_gfn_shared:
>> -            err = ERR_PTR(~X86EMUL_RETRY);
>> -            goto out;
>> +            err = update_map_err(err, ERR_PTR(~X86EMUL_RETRY));
>> +            continue;
>> 
>>          default:
>> -            goto unhandleable;
>> +            err = update_map_err(err, ERR_PTR(~X86EMUL_UNHANDLEABLE));
>> +            continue;
>>          }
>> 
>>          *mfn++ = page_to_mfn(page);
>> 
>>          if ( p2m_is_discard_write(p2mt) )
>> -        {
>> -            err = ERR_PTR(~X86EMUL_OKAY);
>> -            goto out;
>> -        }
>> +            err = update_map_err(err, ERR_PTR(~X86EMUL_OKAY));

... this and ...

>>      }
>> 
>> +    if ( err != ZERO_BLOCK_PTR )
>> +        goto out;

... this.

Jan



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