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KVM: introduce readonly memslot

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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

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

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Xiao Guangrong
2012-08-21 11:02:51 +08:00
committed by Avi Kivity
parent 7068d09715
commit 4d8b81abc4
7 changed files with 102 additions and 28 deletions
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10
Documentation/virtual/kvm/api.txt
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@@ -857,7 +857,8 @@ struct kvm_userspace_memory_region {
};
/* for kvm_memory_region::flags */
#define KVM_MEM_LOG_DIRTY_PAGES 1UL
#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
#define KVM_MEM_READONLY (1UL << 1)
This ioctl allows the user to create or modify a guest physical memory
slot. When changing an existing slot, it may be moved in the guest
@@ -873,9 +874,12 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
be identical. This allows large pages in the guest to be backed by large
pages in the host.
The flags field supports just one flag, KVM_MEM_LOG_DIRTY_PAGES, which
The flags field supports two flag, KVM_MEM_LOG_DIRTY_PAGES, which
instructs kvm to keep track of writes to memory within the slot. See
the KVM_GET_DIRTY_LOG ioctl.
the KVM_GET_DIRTY_LOG ioctl. Another flag is KVM_MEM_READONLY when the
KVM_CAP_READONLY_MEM capability, it indicates the guest memory is read-only,
that means, guest is only allowed to read it. Writes will be posted to
userspace as KVM_EXIT_MMIO exits.
When the KVM_CAP_SYNC_MMU capability, changes in the backing of the memory
region are automatically reflected into the guest. For example, an mmap()