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

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Date:   Mon, 26 Apr 2021 15:43:48 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Cc:     "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        open list <linux-kernel@...r.kernel.org>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Jonathan Corbet <corbet@....net>, Jessica Yu <jeyu@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Will Deacon <will@...nel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <kvmarm@...ts.cs.columbia.edu>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Joerg Roedel <joro@...tes.org>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Jim Mattson <jmattson@...gle.com>,
        Cornelia Huck <cohuck@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "open list:S390" <linux-s390@...r.kernel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Kieran Bingham <kbingham@...nel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "moderated list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <linux-arm-kernel@...ts.infradead.org>,
        James Morse <james.morse@....com>
Subject: Re: [PATCH v2 0/9] KVM: my debug patch queue

On Fri, 2021-04-02 at 10:38 -0700, Paolo Bonzini wrote:
> 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.
Do you mean to add a kvm-unit-test or to add a test to kernel's kvm unit tests
for this?

Best regards,
	Maxim Levitsky

> 
> 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(-)
> >