nEPT: Fix wrong test in kvm_set_cr3
authorNadav Har'El <nyh@il.ibm.com>
Mon, 5 Aug 2013 08:07:08 +0000 (11:07 +0300)
committerPaolo Bonzini <pbonzini@redhat.com>
Wed, 7 Aug 2013 13:57:35 +0000 (15:57 +0200)
commitb7e914501c1d92edc0c30e3bae35c14481642e55
treeeaaed8544710f69976af0b2126dcaa9525256b30
parent3633cfc3e8656a660953e701c189444831f44075
nEPT: Fix wrong test in kvm_set_cr3

kvm_set_cr3() attempts to check if the new cr3 is a valid guest physical
address. The problem is that with nested EPT, cr3 is an *L2* physical
address, not an L1 physical address as this test expects.

As the comment above this test explains, it isn't necessary, and doesn't
correspond to anything a real processor would do. So this patch removes it.

Note that this wrong test could have also theoretically caused problems
in nested NPT, not just in nested EPT. However, in practice, the problem
was avoided: nested_svm_vmexit()/vmrun() do not call kvm_set_cr3 in the
nested NPT case, and instead set the vmcb (and arch.cr3) directly, thus
circumventing the problem. Additional potential calls to the buggy function
are avoided in that we don't trap cr3 modifications when nested NPT is
enabled. However, because in nested VMX we did want to use kvm_set_cr3()
(as requested in Avi Kivity's review of the original nested VMX patches),
we can't avoid this problem and need to fix it.

Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
arch/x86/kvm/x86.c