On Tue, Aug 14, 2012 at 05:00:33PM +0300, Avi Kivity wrote: > On 08/10/2012 09:14 PM, Marcelo Tosatti wrote: > > On Tue, Aug 07, 2012 at 05:47:15PM +0800, Xiao Guangrong wrote: > >> Changelog: > >> - introduce KVM_PFN_ERR_RO_FAULT instead of dummy page > >> - introduce KVM_HVA_ERR_BAD and optimize error hva indicators > >> > >> The test case can be found at: > >> http://lkml.indiana.edu/hypermail/linux/kernel/1207.2/00819/migrate-perf.tar.bz2 > >> > >> In current code, 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. > >> > >> As Avi's suggestion, We introduce readonly memory region to map ROM/ROMD > >> to the guest, read access is happy for readonly memslot, write access on > >> readonly memslot will cause KVM_EXIT_MMIO exit. > > > > Memory slots whose QEMU mapping is write protected is supported > > today, as long as there are no write faults. > > > > What prevents the use of mmap(!MAP_WRITE) to handle read-only memslots > > again? > > Userspace may want to modify the ROM (for example, when programming a > flash device). It is also possible to map an hva range rw through one > slot and ro through another. Right, can do that with multiple userspace maps to the same anonymous memory region (see other email). The bugs noticed should be fixed. -- 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
