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Diffstat (limited to 'Documentation/virt/kvm/x86/errata.rst')
| -rw-r--r-- | Documentation/virt/kvm/x86/errata.rst | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/virt/kvm/x86/errata.rst b/Documentation/virt/kvm/x86/errata.rst index 37c79362a48f..a9cf0e004651 100644 --- a/Documentation/virt/kvm/x86/errata.rst +++ b/Documentation/virt/kvm/x86/errata.rst @@ -48,7 +48,14 @@ versus "has_error_code", i.e. KVM's ABI follows AMD behavior. Nested virtualization features ------------------------------ -TBD +On AMD CPUs, when GIF is cleared, #DB exceptions or traps due to a breakpoint +register match are ignored and discarded by the CPU. The CPU relies on the VMM +to fully virtualize this behavior, even when vGIF is enabled for the guest +(i.e. vGIF=0 does not cause the CPU to drop #DBs when the guest is running). +KVM does not virtualize this behavior as the complexity is unjustified given +the rarity of the use case. One way to handle this would be for KVM to +intercept the #DB, temporarily disable the breakpoint, single-step over the +instruction, then re-enable the breakpoint. x2APIC ------ |