From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Subject: [PATCH v5 00/12] KVM: introduce readonly memslot
Date: Tue, 07 Aug 2012 17:47:15 +0800
Message-ID: <5020E423.9080004@linux.vnet.ibm.com>
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Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
To: Avi Kivity <avi@redhat.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

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.