On 07/28/2010 02:25 PM, Roedel, Joerg wrote:
On Wed, Jul 28, 2010 at 06:28:06AM -0400, Avi Kivity wrote:
We have a slightly different problem, if the nested guest manages to get
an instruction to be emulated by the host (if the guest assigned it the
cirrus framebuffer, for example, so from L1's point of view it is RAM,
but from L0's point of view it is emulated), then we miss the
intercept. L2 could take over L1 this way.
I wonder how this could happen. Shouldn't the shadow paging code take
care of this?
L1 thinks the memory is RAM, so it maps it directly and forgets about
it. L0 knows it isn't, so it leaves it unmapped and emulates any
instruction which accesses it. The emulator needs to check whether the
instruction is intercepted or not.
Note, I think if the instruction operand is in mmio, we're safe, since
the intercept has higher priority than memory access. But if the
instruction itself is on mmio, or if we entered the emulator through smp
trickery, then the emulator will execute the instruction in nested guest
context.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
--
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
