Re: [Xen-devel] [PATCH 3/8] x86/vm-event/monitor: relocate code-motion more appropriately

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.07.16 at 13:02, <czuzu@xxxxxxxxxxxxxxx> wrote:
> On 7/4/2016 1:22 PM, Jan Beulich wrote:
>>>>> On 30.06.16 at 20:43, <czuzu@xxxxxxxxxxxxxxx> wrote:
>>> @@ -119,6 +156,55 @@ bool_t monitored_msr(const struct domain *d, u32 msr)
>>>       return test_bit(msr, bitmap);
>>>   }
>>>   
>>> +static void write_ctrlreg_adjust_traps(struct domain *d)
>>> +{
>>> +    struct vcpu *v;
>>> +    struct arch_vmx_struct *avmx;
>>> +    unsigned int cr3_bitmask;
>>> +    bool_t cr3_vmevent, cr3_ldexit;
>>> +
>>> +    /* Adjust CR3 load-exiting. */
>>> +
>>> +    /* vmx only */
>>> +    ASSERT(cpu_has_vmx);
>>> +
>>> +    /* non-hap domains trap CR3 writes unconditionally */
>>> +    if ( !paging_mode_hap(d) )
>>> +    {
>>> +        for_each_vcpu ( d, v )
>>> +            ASSERT(v->arch.hvm_vmx.exec_control & 
>>> CPU_BASED_CR3_LOAD_EXITING);
>>> +        return;
>>> +    }
>>> +
>>> +    cr3_bitmask = monitor_ctrlreg_bitmask(VM_EVENT_X86_CR3);
>>> +    cr3_vmevent = !!(d->arch.monitor.write_ctrlreg_enabled & cr3_bitmask);
>>> +
>>> +    for_each_vcpu ( d, v )
>>> +    {
>>> +        avmx = &v->arch.hvm_vmx;
>>> +        cr3_ldexit = !!(avmx->exec_control & CPU_BASED_CR3_LOAD_EXITING);
>>> +
>>> +        if ( cr3_vmevent == cr3_ldexit )
>>> +            continue;
>>> +
>>> +        /*
>>> +         * If CR0.PE=0, CR3 load exiting must remain enabled.
>>> +         * See vmx_update_guest_cr code motion for cr = 0.
>>> +         */
>>> +        if ( cr3_ldexit && !hvm_paging_enabled(v) && 
>>> !vmx_unrestricted_guest(v)
>>> )
>>> +            continue;
>>> +
>>> +        if ( cr3_vmevent )
>>> +            avmx->exec_control |= CPU_BASED_CR3_LOAD_EXITING;
>>> +        else
>>> +            avmx->exec_control &= ~CPU_BASED_CR3_LOAD_EXITING;
>>> +
>>> +        vmx_vmcs_enter(v);
>>> +        vmx_update_cpu_exec_control(v);
>>> +        vmx_vmcs_exit(v);
>>> +    }
>>> +}
>> While Razvan gave his ack already, I wonder whether it's really a
>> good idea to put deeply VMX-specific code outside of a VMX-specific
>> file.
> 
> Well, a summary of what this function does would sound like: "adjusts 
> CR3 load-exiting for cr-write monitor vm-events". IMHO that's (monitor) 
> vm-event specific enough to be placed within the vm-event subsystem.
> Could you suggest concretely how this separation would look like? (where 
> to put this function/parts of it (and what parts), what name should it 
> have once moved).

I won't go into that level of detail. Fact is that VMX-specific code
should be kept out of here. Whether you move the entire function
behind a hvm_funcs hook or just part of it is of no interest to me.
In no case should, if and when SVM eventually gets supported for
vm-event/monitor too, this function end up doing both VMX and SVM
specific things.

Jan


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