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    SubjectRe: [PATCH v5 00/12] KVM: introduce readonly memslot
    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?

    The initial objective was to fix a vm crash, can you explain that
    initial problem?



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