Re: [Xen-devel] [PATCH v5 1/4] x86/HVM: fix miscellaneous aspects of x2APIC emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.09.14 at 17:57, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 24/09/14 16:34, Jan Beulich wrote:
>> @@ -877,8 +854,16 @@ static int vlapic_write(struct vcpu *v, 
>>  
>>  int vlapic_apicv_write(struct vcpu *v, unsigned int offset)
>>  {
>> -    uint32_t val = vlapic_get_reg(vcpu_vlapic(v), offset);
>> -    return vlapic_reg_write(v, offset, val);
>> +    struct vlapic *vlapic = vcpu_vlapic(v);
>> +    uint32_t val = vlapic_get_reg(vlapic, offset);
>> +
>> +    if ( !vlapic_x2apic_mode(vlapic) )
>> +        return vlapic_reg_write(v, offset, val);
>> +
>> +    if ( offset != APIC_SELF_IPI )
>> +        return X86EMUL_UNHANDLEABLE;
>> +
>> +    return vlapic_reg_write(v, APIC_ICR, APIC_DEST_SELF | (uint8_t)val);
> 
> (val & APIC_VECTOR_MASK) instead of a uint8_t cast?

Ah, one more case I failed to convert.

>> @@ -891,16 +876,69 @@ int hvm_x2apic_msr_write(struct vcpu *v,
>>  
>>      switch ( offset )
>>      {
>> -        int rc;
>> +    case APIC_TASKPRI:
>> +        if ( msr_content & ~APIC_TPRI_MASK )
>> +            return X86EMUL_UNHANDLEABLE;
>> +        break;
>> +
>> +    case APIC_SPIV:
>> +        if ( msr_content & ~(APIC_VECTOR_MASK | APIC_SPIV_APIC_ENABLED |
>> +                             (VLAPIC_VERSION & APIC_LVR_DIRECTED_EOI
> 
> Need brackets for the logical (VLAPIC_VERSION & APIC_LVR_DIRECTED_EOI)
> test to avoid making a constant expression with the precedence of the
> ternary operator.

Not sure what you mean or what you're thinking here: & has higher
precedence than even &&, not to speak of ?:, so the expression is
quite fine without further parentheses. And yes, the whole ?: is
intended to be a compile time constant, just being prepared for
directed-EOI support to be added (and as this doesn't seem to need
any kind of conditional code, I'm expecting that to get added
directly to the VLAPIC_VERSION #define).

Jan


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