On 05/22/2012 10:27 PM, Avi Kivity wrote: > On 05/22/2012 08:31 AM, Gleb Natapov wrote: >> On Mon, May 21, 2012 at 04:30:41PM -0300, Marcelo Tosatti wrote: >>> On Mon, May 21, 2012 at 04:15:50PM +0800, Xiao Guangrong wrote: >>>> On 05/21/2012 04:08 PM, Gleb Natapov wrote: >>>> >>>>> On Mon, May 21, 2012 at 02:45:45PM +0800, Xiao Guangrong wrote: >>>>>> If we map a readonly memory space from host to guest and the page is >>>>>> not currently mapped in the host, we will get a fault-pfn and async >>>>>> is not allowed, then the vm will crash >>>>>> >>>>> Why would we want to map a readonly memory space from host to guest? >>>>> We may want to do it to support memory semantics on read and mmio on >>>>> write, but do not right now unless something changed while I was not >>>>> looking. >>>> >>>> >>>> Some test cases in kvm-unit-tests and the benchmark i am writing for KVM >>>> need map the function on host to guest. >>> >>> Or ROM. Or read-only mappings of IVSHMEM (which don't exist yet). >> True. KVM should ignore writes to such areas, not kill a guest. Is this >> how the code works today? >> > > Right now qemu maps ROM as RAM. There is no way to tell kvm that > something is ROM (or ROMD). > > There are two options for that: > - mprotect() the ROM, and teach kvm about read-only areas (this patch); > but that doesn't work if we have a read-only and a writable alias of the > same area > - add a flag indicating that an area is ROM or ROMD > > I prefer the latter, because of the alias issue. > I agree. Will post a new patch to do it if other guys do not object it. :) -- 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
