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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id dh16sm622370edb.63.2021.09.21.23.42.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Sep 2021 23:42:33 -0700 (PDT) Subject: Re: [PATCH v3 00/16] perf: KVM: Fix, optimize, and clean up callbacks To: Sean Christopherson , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Will Deacon , Mark Rutland , Marc Zyngier , Guo Ren , Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Boris Ostrovsky , Juergen Gross Cc: Alexander Shishkin , Jiri Olsa , Namhyung Kim , James Morse , Alexandru Elisei , Suzuki K Poulose , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Stefano Stabellini , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-csky@vger.kernel.org, linux-riscv@lists.infradead.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, Artem Kashkanov , Like Xu , Zhu Lingshan References: <20210922000533.713300-1-seanjc@google.com> From: Paolo Bonzini Message-ID: Date: Wed, 22 Sep 2021 08:42:31 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210922000533.713300-1-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/09/21 02:05, Sean Christopherson wrote: > Peter, I left the Intel PT mess as-is. Having to pass a NULL pointer > from KVM arm64 seemed to be a lesser evil than more exports and multiple > registration paths. > > This is a combination of ~2 series to fix bugs in the perf+KVM callbacks, > optimize the callbacks by employing static_call, and do a variety of > cleanup in both perf and KVM. > > Patch 1 fixes a mostly-theoretical bug where perf can deref a NULL > pointer if KVM unregisters its callbacks while they're being accessed. > In practice, compilers tend to avoid problematic reloads of the pointer > and the PMI handler doesn't lose the race against module unloading, > i.e doesn't hit a use-after-free. > > Patches 2 and 3 fix an Intel PT handling bug where KVM incorrectly > eats PT interrupts when PT is supposed to be owned entirely by the host. > > Patches 4-9 clean up perf's callback infrastructure and switch to > static_call for arm64 and x86 (the only survivors). > > Patches 10-16 clean up related KVM code and unify the arm64/x86 callbacks. > > Based on "git://git.kernel.org/pub/scm/virt/kvm/kvm.git queue", commit > 680c7e3be6a3 ("KVM: x86: Exit to userspace ..."). Looks nice apart from a couple nits, I will gladly accept a topic branch with both the perf and the KVM parts. Thanks, Paolo > v3: > - Add wrappers for guest callbacks to that stubs can be provided when > GUEST_PERF_EVENTS=n. > - s/HAVE_GUEST_PERF_EVENTS/GUEST_PERF_EVENTS and select it from KVM > and XEN_PV instead of from top-level arm64/x86. [Paolo] > - Drop an unnecessary synchronize_rcu() when registering callbacks. [Peter] > - Retain a WARN_ON_ONCE() when unregistering callbacks if the caller > didn't provide the correct pointer. [Peter] > - Rework the static_call patch to move it all to common perf. > - Add a patch to drop the (un)register stubs, made possible after > having KVM+XEN_PV select GUEST_PERF_EVENTS. > - Split dropping guest callback "support" for arm, csky, etc... to a > separate patch, to make introducing GUEST_PERF_EVENTS cleaner. > > v2 (relative to static_call v10): > - Split the patch into the semantic change (multiplexed ->state) and > introduction of static_call. > - Don't use '0' for "not a guest RIP". > - Handle unregister path. > - Drop changes for architectures that can be culled entirely. > > v2 (relative to v1): > - https://lkml.kernel.org/r/20210828003558.713983-6-seanjc@google.com > - Drop per-cpu approach. [Peter] > - Fix mostly-theoretical reload and use-after-free with READ_ONCE(), > WRITE_ONCE(), and synchronize_rcu(). [Peter] > - Avoid new exports like the plague. [Peter] > > v1: > - https://lkml.kernel.org/r/20210827005718.585190-1-seanjc@google.com > > v10 static_call: > - https://lkml.kernel.org/r/20210806133802.3528-2-lingshan.zhu@intel.com > > > Like Xu (1): > perf/core: Rework guest callbacks to prepare for static_call support > > Sean Christopherson (15): > perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and > deref > KVM: x86: Register perf callbacks after calling vendor's > hardware_setup() > KVM: x86: Register Processor Trace interrupt hook iff PT enabled in > guest > perf: Stop pretending that perf can handle multiple guest callbacks > perf: Drop dead and useless guest "support" from arm, csky, nds32 and > riscv > perf: Add wrappers for invoking guest callbacks > perf: Force architectures to opt-in to guest callbacks > perf/core: Use static_call to optimize perf_guest_info_callbacks > KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu > variable > KVM: x86: More precisely identify NMI from guest when handling PMI > KVM: Move x86's perf guest info callbacks to generic KVM > KVM: x86: Move Intel Processor Trace interrupt handler to vmx.c > KVM: arm64: Convert to the generic perf callbacks > KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / > pmu.c > perf: Drop guest callback (un)register stubs > > arch/arm/kernel/perf_callchain.c | 28 ++------------ > arch/arm64/include/asm/kvm_host.h | 9 ++++- > arch/arm64/kernel/perf_callchain.c | 13 ++++--- > arch/arm64/kvm/Kconfig | 1 + > arch/arm64/kvm/Makefile | 2 +- > arch/arm64/kvm/arm.c | 11 +++++- > arch/arm64/kvm/perf.c | 62 ------------------------------ > arch/arm64/kvm/pmu.c | 8 ++++ > arch/csky/kernel/perf_callchain.c | 10 ----- > arch/nds32/kernel/perf_event_cpu.c | 29 ++------------ > arch/riscv/kernel/perf_callchain.c | 10 ----- > arch/x86/events/core.c | 13 ++++--- > arch/x86/events/intel/core.c | 5 +-- > arch/x86/include/asm/kvm_host.h | 7 +++- > arch/x86/kvm/Kconfig | 1 + > arch/x86/kvm/pmu.c | 2 +- > arch/x86/kvm/svm/svm.c | 2 +- > arch/x86/kvm/vmx/vmx.c | 25 +++++++++++- > arch/x86/kvm/x86.c | 58 +++++----------------------- > arch/x86/kvm/x86.h | 17 ++++++-- > arch/x86/xen/Kconfig | 1 + > arch/x86/xen/pmu.c | 32 +++++++-------- > include/kvm/arm_pmu.h | 1 + > include/linux/kvm_host.h | 10 +++++ > include/linux/perf_event.h | 41 ++++++++++++++------ > init/Kconfig | 4 ++ > kernel/events/core.c | 39 +++++++++++++------ > virt/kvm/kvm_main.c | 44 +++++++++++++++++++++ > 28 files changed, 235 insertions(+), 250 deletions(-) > delete mode 100644 arch/arm64/kvm/perf.c >