Re: [PATCH v2 0/9] KVM: my debug patch queue

Paolo Bonzini
2021-04-02T17:38:51Z

On 01/04/21 15:54, Maxim Levitsky wrote:
> Hi!
>
> I would like to publish two debug features which were needed for other stuff
> I work on.
>
> One is the reworked lx-symbols script which now actually works on at least
> gdb 9.1 (gdb 9.2 was reported to fail to load the debug symbols from the kernel
> for some reason, not related to this patch) and upstream qemu.

Queued patches 2-5 for now. 6 is okay but it needs a selftest. (e.g.
using KVM_VCPU_SET_EVENTS) and the correct name for the constant.

Paolo

> The other feature is the ability to trap all guest exceptions (on SVM for now)
> and see them in kvmtrace prior to potential merge to double/triple fault.
>
> This can be very useful and I already had to manually patch KVM a few
> times for this.
> I will, once time permits, implement this feature on Intel as well.
>
> V2:
>
> * Some more refactoring and workarounds for lx-symbols script
>
> * added KVM_GUESTDBG_BLOCKEVENTS flag to enable 'block interrupts on
> single step' together with KVM_CAP_SET_GUEST_DEBUG2 capability
> to indicate which guest debug flags are supported.
>
> This is a replacement for unconditional block of interrupts on single
> step that was done in previous version of this patch set.
> Patches to qemu to use that feature will be sent soon.
>
> * Reworked the the 'intercept all exceptions for debug' feature according
> to the review feedback:
>
> - renamed the parameter that enables the feature and
> moved it to common kvm module.
> (only SVM part is currently implemented though)
>
> - disable the feature for SEV guests as was suggested during the review
> - made the vmexit table const again, as was suggested in the review as well.
>
> Best regards,
> Maxim Levitsky
>
> Maxim Levitsky (9):
> scripts/gdb: rework lx-symbols gdb script
> KVM: introduce KVM_CAP_SET_GUEST_DEBUG2
> KVM: x86: implement KVM_CAP_SET_GUEST_DEBUG2
> KVM: aarch64: implement KVM_CAP_SET_GUEST_DEBUG2
> KVM: s390x: implement KVM_CAP_SET_GUEST_DEBUG2
> KVM: x86: implement KVM_GUESTDBG_BLOCKEVENTS
> KVM: SVM: split svm_handle_invalid_exit
> KVM: x86: add force_intercept_exceptions_mask
> KVM: SVM: implement force_intercept_exceptions_mask
>
> Documentation/virt/kvm/api.rst | 4 +
> arch/arm64/include/asm/kvm_host.h | 4 +
> arch/arm64/kvm/arm.c | 2 +
> arch/arm64/kvm/guest.c | 5 -
> arch/s390/include/asm/kvm_host.h | 4 +
> arch/s390/kvm/kvm-s390.c | 3 +
> arch/x86/include/asm/kvm_host.h | 12 ++
> arch/x86/include/uapi/asm/kvm.h | 1 +
> arch/x86/kvm/svm/svm.c | 87 +++++++++++--
> arch/x86/kvm/svm/svm.h | 6 +-
> arch/x86/kvm/x86.c | 14 ++-
> arch/x86/kvm/x86.h | 2 +
> include/uapi/linux/kvm.h | 1 +
> kernel/module.c | 8 +-
> scripts/gdb/linux/symbols.py | 203 ++++++++++++++++++++----------
> 15 files changed, 272 insertions(+), 84 deletions(-)
>