linux-kernel - Re: [PATCH v3 0/6] KVM: my debug patch queue

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Date:   Wed, 11 Aug 2021 15:10:43 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Kieran Bingham <kbingham@...nel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Andrew Jones <drjones@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Johannes Berg <johannes.berg@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        "H. Peter Anvin" <hpa@...or.com>, Jessica Yu <jeyu@...nel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Yang Weijiang <weijiang.yang@...el.com>,
        linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Shuah Khan <shuah@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 0/6] KVM: my debug patch queue

On 11/08/21 14:29, 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.
> 
> 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_BLOCKIRQ 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.
> 
> V3:
>   * Modified a selftest to cover the KVM_GUESTDBG_BLOCKIRQ
>   * Rebased on kvm/queue
> 
> Best regards,
>          Maxim Levitsky
> 
> Maxim Levitsky (6):
>    KVM: SVM: split svm_handle_invalid_exit
>    KVM: x86: add force_intercept_exceptions_mask
>    KVM: SVM: implement force_intercept_exceptions_mask
>    scripts/gdb: rework lx-symbols gdb script
>    KVM: x86: implement KVM_GUESTDBG_BLOCKIRQ
>    KVM: selftests: test KVM_GUESTDBG_BLOCKIRQ
> 
>   Documentation/virt/kvm/api.rst                |   1 +
>   arch/x86/include/asm/kvm_host.h               |   5 +-
>   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                            |  12 +-
>   arch/x86/kvm/x86.h                            |   2 +
>   kernel/module.c                               |   8 +-
>   scripts/gdb/linux/symbols.py                  | 203 ++++++++++++------
>   .../testing/selftests/kvm/x86_64/debug_regs.c |  24 ++-
>   10 files changed, 266 insertions(+), 83 deletions(-)
> 

Queued 1-5-6.

For patches 2 and 3, please add VMX support too.

For patch 4, it's not KVM :) so please submit it separately.

Paolo