On 9/27/19 11:45 PM, Sean Christopherson wrote: > *sigh* > > v2 was shaping up to be a trivial update, until I started working on > Vitaly's suggestion to add a helper to test for register availability. > > The primary purpose of this series is to fix a CR3 corruption in L2 > reported by Reto Buerki when running with HLT interception disabled in L1. > On a nested VM-Enter that puts L2 into HLT, KVM never actually enters L2 > and instead mimics HLT interception by canceling the nested run and > pretending that VM-Enter to L2 completed and then exited on HLT (which > KVM intercepted). Because KVM never actually runs L2, KVM skips the > pending MMU update for L2 and so leaves a stale value in vmcs02.GUEST_CR3. > If the next wake event for L2 triggers a nested VM-Exit, KVM will refresh > vmcs12->guest_cr3 from vmcs02.GUEST_CR3 and consume the stale value. > > Fix the issue by unconditionally writing vmcs02.GUEST_CR3 during nested > VM-Enter instead of deferring the update to vmx_set_cr3(), and skip the > update of GUEST_CR3 in vmx_set_cr3() when running L2. I.e. make the > nested code fully responsible for vmcs02.GUEST_CR3. > > Patch 02/08 is a minor optimization to skip the GUEST_CR3 update if > vmcs01 is already up-to-date. > > Patches 03 and beyond are Vitaly's fault ;-). > > Patches 03 and 04 are tangentially related cleanup to vmx_set_rflags() > that was discovered when working through the avail/dirty testing code. > Ideally they'd be sent as a separate series, but they conflict with the > avail/dirty helper changes and are themselves minor and straightforward. > > Patches 05 and 06 clean up the register caching code so that there is a > single enum for all registers which use avail/dirty tracking. While not > a true prerequisite for the avail/dirty helpers, the cleanup allows the > new helpers to take an 'enum kvm_reg' instead of a less helpful 'int reg'. > > Patch 07 is the helpers themselves, as suggested by Vitaly. > > Patch 08 is a truly optional change to ditch decache_cr3() in favor of > handling CR3 via cache_reg() like any other avail/dirty register. > > > Note, I collected the Reviewed-by and Tested-by tags for patches 01 and 02 > even though I inverted the boolean from 'skip_cr3' to 'update_guest_cr3'. > Please drop the tags if that constitutes a non-trivial functional change. > > v2: > - Invert skip_cr3 to update_guest_cr3. [Liran] > - Reword the changelog and comment to be more explicit in detailing > how/when KVM will process a nested VM-Enter without runnin L2. [Liran] > - Added Reviewed-by and Tested-by tags. > - Add a comment in vmx_set_cr3() to explicitly state that nested > VM-Enter is responsible for loading vmcs02.GUEST_CR3. [Jim] > - All of the loveliness in patches 03-08. [Vitaly] > > Sean Christopherson (8): > KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter > KVM: VMX: Skip GUEST_CR3 VMREAD+VMWRITE if the VMCS is up-to-date > KVM: VMX: Consolidate to_vmx() usage in RFLAGS accessors > KVM: VMX: Optimize vmx_set_rflags() for unrestricted guest > KVM: x86: Add WARNs to detect out-of-bounds register indices > KVM: x86: Fold 'enum kvm_ex_reg' definitions into 'enum kvm_reg' > KVM: x86: Add helpers to test/mark reg availability and dirtiness > KVM: x86: Fold decache_cr3() into cache_reg() > > arch/x86/include/asm/kvm_host.h | 5 +- > arch/x86/kvm/kvm_cache_regs.h | 67 +++++++++++++++++------ > arch/x86/kvm/svm.c | 5 -- > arch/x86/kvm/vmx/nested.c | 14 ++++- > arch/x86/kvm/vmx/vmx.c | 94 ++++++++++++++++++--------------- > arch/x86/kvm/x86.c | 13 ++--- > arch/x86/kvm/x86.h | 6 +-- > 7 files changed, 123 insertions(+), 81 deletions(-) Series: Tested-by: Reto Buerki <reet@xxxxxxxxxxx> Thanks.
