On Tue, Aug 21, 2012 at 05:06:57PM +0300, Avi Kivity wrote: > It turns out that our big real mode implementation was based on a miconception: > I believed that loading a segment register in real mode causes the limit to be > reset to 0xffff (thus undoing the effect), while in reality, the limit is preserved > across segment changes. This bug was hidden by another bug: we didn't do limit checks > in real mode. So even though segment loads corrupted the limit, the guest still > functioned because that limit isn't checked. > > This patchset fixes both bugs, and introduces an optimization: we can now use > vm86 mode to virtualize big real mode (under usually-met conditions). This > both speeds up big real mode, and makes it more robust, since fewer instructions > need to be emulated. > > I think this patchset means we can remove emulate_invalid_guest_state=0, since it > offers no advantages now. > > Avi Kivity (13): > KVM: VMX: Separate saving pre-realmode state from setting segments > KVM: VMX: Fix incorrect lookup of segment S flag in > fix_pmode_dataseg() > KVM: VMX: Use kvm_segment to save protected-mode segments when > entering realmode > KVM: VMX: Retain limit and attributes when entering protected mode > KVM: VMX: Allow real mode emulation using vm86 with dpl=0 > KVM: VMX: Allow vm86 virtualization of big real mode > KVM: x86 emulator: Leave segment limit and attributs alone in real > mode > KVM: x86 emulator: Check segment limits in real mode too > KVM: x86 emulator: Fix #GP error code during linearization > KVM: VMX: Return real real-mode segment data even if > emulate_invalid_guest_state=1 > KVM: VMX: Preserve segment limit and access rights in real mode > KVM: VMX: Save all segment data in real mode > KVM: VMX: Ignore segment G and D bits when considering whether we can > virtualize > > arch/x86/kvm/emulate.c | 19 ++++------ > arch/x86/kvm/vmx.c | 100 ++++++++++++++++++------------------------------- > 2 files changed, 44 insertions(+), 75 deletions(-) Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
