On Tue, Sep 03, 2013 at 07:45:47PM +0800, Arthur Chunqi Li wrote: > On Tue, Sep 3, 2013 at 7:19 PM, Gleb Natapov <gleb@xxxxxxxxxx> wrote: > > On Mon, Aug 12, 2013 at 08:35:57PM +0800, Arthur Chunqi Li wrote: > >> Hi Gleb and Paolo, > >> There are some corner cases when testing I/O bitmaps, and I don't know > >> the exact action of HW. > >> > > A little bit late but... > A little earlier mail, but you are warming up quickly, maybe it's a > tough time in the past week ;) > > > >> 1. If we set bit of 0x4000 in bitmap and call inl(0x3FFFF) or > >> inl(0x4000) in guest, what will get of exit information? > >> > > Spec says; > > execution of an I/O instruction causes a VM exit if any bit in the I/O > > bitmaps corresponding to a port it accesses is 1. Note "any" here. The > > exit will have address that instruction used, otherwise how can we be > > able to emulate it properly. > > > >> 2. What will we get when calling inl(0xFFFF) in guest with/without > >> “unconditional I/O exiting” VM-execution control and “use I/O bitmaps” > >> VM-execution control? > > In other words are you asking what happens if you do inl(0xFFFF) on real > > HW? > > > > "The result of an attempt to address beyond the I/O address space limit of > > FFFFH is implementation-specific" > > > >> > >> I test the two cases in nested env. For the first one, I got normal > >> exit if any of the port accessed is masked in bitmap. For the second, > >> it will acts the same as other ports. And the SDM says "If an I/O > >> operation “wraps around” the 16-bit I/O-port space (accesses ports > >> FFFFH and 0000H), the I/O instruction causes a VM exit." I cannot find > >> the exact reaction of this case. > > What do you mean by "exact reaction"? > As to my understanding, any "wrap around" access to 0xFFFF will cause > VM exit even though mask of 0xFFFF is not set, but this is only my > guess. I cannot get what inl(0xFFFF) will result described in SDM. But > as what you said above, we do not need to test inl(0xFFFF) because we > are not expected to get a determined result. > Implementation-specific behaviour is only for what happens on real HW. In non root operation spec says VM exit should happen and we should test for that. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
