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

[Gleb Natapov <gleb@cloudius-systems.com>]

On Wed, Dec 03, 2014 at 05:50:33PM +0800, Zhang Haoyu wrote:
> 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.

--
			Gleb.