Re: [PATCH] KVM: fix async page fault working for readonly mapping

From: Marcelo Tosatti
Date: Mon May 21 2012 - 15:35:35 EST


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).

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