Re: What's the difference between EPT_MISCONFIG and EPT_VIOLATION?

["Zhang Haoyu" <zhanghy@sangfor.com>]

> > Hi,
> > 
> > EXIT_REASON_EPT_VIOLATION's corresponding handle is handle_ept_violation(),
> > and EXIT_REASON_EPT_MISCONFIG's corresponding handle is handle_ept_misconfig(),
> > what's the difference between them?
> > 
> > I read the SDM-3C 28.2.3 EPT-Induced VM Exits, and found below description,
> > "An EPT misconfiguration occurs when, in the course of translating 
> > a guest-physical address, the logical processor encounters an EPT 
> > paging-structure entry that contains an unsupported value. An EPT 
> > violation occurs when there is no EPT misconfiguration but the EPT 
> > paging-structure entries disallow an access using the guest physical
> > address."
> > 
> > According to above description, EPT-MISCONFIG is from error settings ,
> > but from the its exit-handle handle_ept_misconfig(),
> > it seems that handle_ept_misconfig() handles mmio pagefault,
> > I'm really confused, I think I'm missing something,
> > any advices?
> > 
> EXIT_REASON_EPT_VIOLATION is similar to a "page not present" pagefault
> EXIT_REASON_EPT_MISCONFIG is similar to a "reserved bit set" pagefault.
> handle_ept_misconfig() handles mmio pagefault because KVM has an
> optimization that uses reserved bits to mark mmio regions.
>
Thanks, Gleb, 
where does kvm use the reserved bits to mark mmio regions?

> --
> 			Gleb.