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authorSean Christopherson <sean.j.christopherson@intel.com>2020-04-16 03:07:39 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2020-04-21 16:13:09 +0300
commitb8d295f96b6c9745d7eebee622690e0e835c63af (patch)
tree1ea185121d41d5ec121422bf758397870f05b554 /Documentation/virt
parentc36b71503a2268206ebeda6697094ffb4e7e94c2 (diff)
downloadlinux-b8d295f96b6c9745d7eebee622690e0e835c63af.tar.xz
KVM: nVMX: Remove non-functional "support" for CR3 target values
Remove all references to cr3_target_value[0-3] and replace the fields in vmcs12 with "dead_space" to preserve the vmcs12 layout. KVM doesn't support emulating CR3-target values, despite a variety of code that implies otherwise, as KVM unconditionally reports '0' for the number of supported CR3-target values. This technically fixes a bug where KVM would incorrectly allow VMREAD and VMWRITE to nonexistent fields, i.e. cr3_target_value[0-3]. Per Intel's SDM, the number of supported CR3-target values reported in VMX_MISC also enumerates the existence of the associated VMCS fields: If a future implementation supports more than 4 CR3-target values, they will be encoded consecutively following the 4 encodings given here. Alternatively, the "bug" could be fixed by actually advertisting support for 4 CR3-target values, but that'd likely just enable kvm-unit-tests given that no one has complained about lack of support for going on ten years, e.g. KVM, Xen and HyperV don't use CR3-target values. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200416000739.9012-1-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt')
-rw-r--r--Documentation/virt/kvm/nested-vmx.rst5
1 files changed, 1 insertions, 4 deletions
diff --git a/Documentation/virt/kvm/nested-vmx.rst b/Documentation/virt/kvm/nested-vmx.rst
index 592b0ab6970b..89851cbb7df9 100644
--- a/Documentation/virt/kvm/nested-vmx.rst
+++ b/Documentation/virt/kvm/nested-vmx.rst
@@ -116,10 +116,7 @@ struct shadow_vmcs is ever changed.
natural_width cr4_guest_host_mask;
natural_width cr0_read_shadow;
natural_width cr4_read_shadow;
- natural_width cr3_target_value0;
- natural_width cr3_target_value1;
- natural_width cr3_target_value2;
- natural_width cr3_target_value3;
+ natural_width dead_space[4]; /* Last remnants of cr3_target_value[0-3]. */
natural_width exit_qualification;
natural_width guest_linear_address;
natural_width guest_cr0;