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authorTakuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>2013-01-30 19:40:41 +0900
committerMarcelo Tosatti <mtosatti@redhat.com>2013-02-04 22:56:47 -0200
commit75d61fbcf563373696578570e914f555e12c8d97 (patch)
tree8835d8a5cf79704569f568675792672c930746ae /Documentation/virtual
parentf64c0398939483eb1d8951f24fbc21e94ed54457 (diff)
KVM: set_memory_region: Disallow changing read-only attribute later
As Xiao pointed out, there are a few problems with it: - kvm_arch_commit_memory_region() write protects the memory slot only for GET_DIRTY_LOG when modifying the flags. - FNAME(sync_page) uses the old spte value to set a new one without checking KVM_MEM_READONLY flag. Since we flush all shadow pages when creating a new slot, the simplest fix is to disallow such problematic flag changes: this is safe because no one is doing such things. Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Cc: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt12
1 files changed, 6 insertions, 6 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 09905cbcbb0..0e03b196827 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -874,12 +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 two flag, KVM_MEM_LOG_DIRTY_PAGES, which instructs
-kvm to keep track of writes to memory within the slot. See KVM_GET_DIRTY_LOG
-ioctl. The KVM_CAP_READONLY_MEM capability indicates the availability of the
-KVM_MEM_READONLY flag. When this flag is set for a memory region, KVM only
-allows read accesses. Writes will be posted to userspace as KVM_EXIT_MMIO
-exits.
+The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
+KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of
+writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to
+use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
+to make a new slot read-only. In this case, writes to this memory will be
+posted to userspace as KVM_EXIT_MMIO exits.
When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
the memory region are automatically reflected into the guest. For example, an