From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CAA33C07E95 for ; Mon, 19 Jul 2021 18:50:06 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 3A4F56108B for ; Mon, 19 Jul 2021 18:50:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A4F56108B Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8D0EB4B0D7; Mon, 19 Jul 2021 14:50:05 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@google.com Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 257LkT+cUjBl; Mon, 19 Jul 2021 14:50:03 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id CB2804B0B5; Mon, 19 Jul 2021 14:50:03 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8A0894B0BB for ; Mon, 19 Jul 2021 14:50:02 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id dX+Z-u-L5rxz for ; Mon, 19 Jul 2021 14:50:01 -0400 (EDT) Received: from mail-io1-f74.google.com (mail-io1-f74.google.com [209.85.166.74]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 0E88A4086D for ; Mon, 19 Jul 2021 14:50:01 -0400 (EDT) Received: by mail-io1-f74.google.com with SMTP id s203-20020a6b2cd40000b0290528db19d5b3so11949075ios.5 for ; Mon, 19 Jul 2021 11:50:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=TW3Lwfo6iV3YWWKfTQZnRqKolgBnoTBJnEoEOlUBBIU=; b=Ka7NIFYp8eL6xwNwJff+OsKuklDUlOD9dQVG8L4hhr8zIJMW0+qvq3OmyK3dBb39aM dVauf6jg209m/BQbQ6WkBJl/Hi6q/5zWGvlKuZw1OhXPVhqAFOnnBf+ntdqe2DLKCRDb SI9Kk4VLposrYS16Prq2KpqODez2UdyxnMY6SyXquz0GumkWt1cSa2TmBAGvCPZExGf6 0IhUVBp5oReWE9HG9T4D8o6rEkh0BmrtjlmhVaHK+1KMWwnGRh7ERe5wbCCmI2aigQRd iS4kdmz3knct394pqegei0v3g0IySWFV+Qai5NY/SheK2Fj1Fq8vI5+bGXjvuJdjFEeN mtUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=TW3Lwfo6iV3YWWKfTQZnRqKolgBnoTBJnEoEOlUBBIU=; b=gpNiwBg51tob7XWviJZjcwVpJ19OEKWlz6yE6Hf6ikz1YAgKhoLLuG7NZLglOjKaYh 5hBwS768cNBeq7CB5U+eaPgniA9nECBkRu1k8b/YrDh1+23r8dyu24sQ9IlhImpQFD1N gnO43mtf0+0izvS0jgdWF+B3rFyaNg0iUhUR+J4qs6Eiq8gWaySftGLx4wWgKryjT2YN 08bNcBDSeOZifsB/M0Y9wrSHkPP1U25UGIoUqXpJoZ+eQ9cDS19dFfIfEyc4tzZ7Htpo BDAmbnICC2mimm3uuXNafYPmK3+yxHA77yycJaj8iYsQVMZuDvpinGDBhJ9iqFe9uS0C pB7w== X-Gm-Message-State: AOAM533j/qWPh/vYNEKsuICvNxaxcIPMDZwmyJuVRZP1zXtvQey8UCLB 9qeC8tbeJ+ZhBCzuQakj6l7H4xV2tqw= X-Google-Smtp-Source: ABdhPJxAZWRt/inMp7xN5+GhnqHLkGfanEok2D7yX9AeIFdWV2Eh47/OPmYvAnECuaXJ0ytjYuFl7s1PqIk= X-Received: from oupton.c.googlers.com ([fda3:e722:ac3:cc00:2b:ff92:c0a8:404]) (user=oupton job=sendgmr) by 2002:a05:6602:2099:: with SMTP id a25mr1891457ioa.143.1626720600237; Mon, 19 Jul 2021 11:50:00 -0700 (PDT) Date: Mon, 19 Jul 2021 18:49:37 +0000 Message-Id: <20210719184949.1385910-1-oupton@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.32.0.402.g57bb445576-goog Subject: [PATCH v3 00/12] KVM: Add idempotent controls for migrating system counter state From: Oliver Upton To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: Marc Zyngier , Raghavendra Rao Anata , Peter Shier , Sean Christopherson , David Matlack , Paolo Bonzini , linux-arm-kernel@lists.infradead.org, Jim Mattson X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu KVM's current means of saving/restoring system counters is plagued with temporal issues. At least on ARM64 and x86, we migrate the guest's system counter by-value through the respective guest system register values (cntvct_el0, ia32_tsc). Restoring system counters by-value is brittle as the state is not idempotent: the host system counter is still oscillating between the attempted save and restore. Furthermore, VMMs may wish to transparently live migrate guest VMs, meaning that they include the elapsed time due to live migration blackout in the guest system counter view. The VMM thread could be preempted for any number of reasons (scheduler, L0 hypervisor under nested) between the time that it calculates the desired guest counter value and when KVM actually sets this counter state. Despite the value-based interface that we present to userspace, KVM actually has idempotent guest controls by way of system counter offsets. We can avoid all of the issues associated with a value-based interface by abstracting these offset controls in new ioctls. This series introduces new vCPU device attributes to provide userspace access to the vCPU's system counter offset. Patch 1 adopts Paolo's suggestion, augmenting the KVM_{GET,SET}_CLOCK ioctls to provide userspace with a (host_tsc, realtime) instant. This is essential for a VMM to perform precise migration of the guest's system counters. Patches 2-3 add support for x86 by shoehorning the new controls into the pre-existing synchronization heuristics. Patches 4-5 implement a test for the new additions to KVM_{GET,SET}_CLOCK. Patches 6-7 implement at test for the tsc offset attribute introduced in patch 3. Patch 8 adds a device attribute for the arm64 virtual counter-timer offset. Patch 9 extends the test from patch 7 to cover the arm64 virtual counter-timer offset. Patch 10 adds a device attribute for the arm64 physical counter-timer offset. Currently, this is implemented as a synthetic register, forcing the guest to trap to the host and emulating the offset in the fast exit path. Later down the line we will have hardware with FEAT_ECV, which allows the hypervisor to perform physical counter-timer offsetting in hardware (CNTPOFF_EL2). Patch 11 extends the test from patch 7 to cover the arm64 physical counter-timer offset. Patch 12 introduces a benchmark to measure the overhead of emulation in patch 10. Physical counter benchmark -------------------------- The following data was collected by running 10000 iterations of the benchmark test from Patch 6 on an Ampere Mt. Jade reference server, A 2S machine with 2 80-core Ampere Altra SoCs. Measurements were collected for both VHE and nVHE operation using the `kvm-arm.mode=` command-line parameter. nVHE ---- +--------------------+--------+---------+ | Metric | Native | Trapped | +--------------------+--------+---------+ | Average | 54ns | 148ns | | Standard Deviation | 124ns | 122ns | | 95th Percentile | 258ns | 348ns | +--------------------+--------+---------+ VHE --- +--------------------+--------+---------+ | Metric | Native | Trapped | +--------------------+--------+---------+ | Average | 53ns | 152ns | | Standard Deviation | 92ns | 94ns | | 95th Percentile | 204ns | 307ns | +--------------------+--------+---------+ This series applies cleanly to the following commit: 1889228d80fe ("KVM: selftests: smm_test: Test SMM enter from L2") v1 -> v2: - Reimplemented as vCPU device attributes instead of a distinct ioctl. - Added the (realtime, host_tsc) instant support to KVM_{GET,SET}_CLOCK - Changed the arm64 implementation to broadcast counter offset values to all vCPUs in a guest. This upholds the architectural expectations of a consistent counter-timer across CPUs. - Fixed a bug with traps in VHE mode. We now configure traps on every transition into a guest to handle differing VMs (trapped, emulated). v2 -> v3: - Added documentation for additions to KVM_{GET,SET}_CLOCK - Added documentation for all new vCPU attributes - Added documentation for suggested algorithm to migrate a guest's TSC(s) - Bug fixes throughout series - Rename KVM_CLOCK_REAL_TIME -> KVM_CLOCK_REALTIME v1: https://lore.kernel.org/kvm/20210608214742.1897483-1-oupton@google.com/ v2: https://lore.kernel.org/r/20210716212629.2232756-1-oupton@google.com Oliver Upton (12): KVM: x86: Report host tsc and realtime values in KVM_GET_CLOCK KVM: x86: Refactor tsc synchronization code KVM: x86: Expose TSC offset controls to userspace tools: arch: x86: pull in pvclock headers selftests: KVM: Add test for KVM_{GET,SET}_CLOCK selftests: KVM: Add helpers for vCPU device attributes selftests: KVM: Introduce system counter offset test KVM: arm64: Allow userspace to configure a vCPU's virtual offset selftests: KVM: Add support for aarch64 to system_counter_offset_test KVM: arm64: Provide userspace access to the physical counter offset selftests: KVM: Test physical counter offsetting selftests: KVM: Add counter emulation benchmark Documentation/virt/kvm/api.rst | 42 +- Documentation/virt/kvm/devices/vcpu.rst | 101 +++++ Documentation/virt/kvm/locking.rst | 11 + arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/include/asm/kvm_hyp.h | 2 - arch/arm64/include/asm/sysreg.h | 1 + arch/arm64/include/uapi/asm/kvm.h | 2 + arch/arm64/kvm/arch_timer.c | 118 ++++- arch/arm64/kvm/arm.c | 4 +- arch/arm64/kvm/hyp/include/hyp/switch.h | 23 + arch/arm64/kvm/hyp/include/hyp/timer-sr.h | 26 ++ arch/arm64/kvm/hyp/nvhe/switch.c | 2 - arch/arm64/kvm/hyp/nvhe/timer-sr.c | 21 +- arch/arm64/kvm/hyp/vhe/timer-sr.c | 27 ++ arch/x86/include/asm/kvm_host.h | 4 + arch/x86/include/uapi/asm/kvm.h | 4 + arch/x86/kvm/x86.c | 422 ++++++++++++++---- include/kvm/arm_arch_timer.h | 2 - include/uapi/linux/kvm.h | 7 +- tools/arch/x86/include/asm/pvclock-abi.h | 48 ++ tools/arch/x86/include/asm/pvclock.h | 103 +++++ tools/testing/selftests/kvm/.gitignore | 3 + tools/testing/selftests/kvm/Makefile | 4 + .../kvm/aarch64/counter_emulation_benchmark.c | 215 +++++++++ .../selftests/kvm/include/aarch64/processor.h | 24 + .../testing/selftests/kvm/include/kvm_util.h | 11 + tools/testing/selftests/kvm/lib/kvm_util.c | 38 ++ .../kvm/system_counter_offset_test.c | 206 +++++++++ .../selftests/kvm/x86_64/kvm_clock_test.c | 210 +++++++++ 29 files changed, 1549 insertions(+), 133 deletions(-) create mode 100644 arch/arm64/kvm/hyp/include/hyp/timer-sr.h create mode 100644 tools/arch/x86/include/asm/pvclock-abi.h create mode 100644 tools/arch/x86/include/asm/pvclock.h create mode 100644 tools/testing/selftests/kvm/aarch64/counter_emulation_benchmark.c create mode 100644 tools/testing/selftests/kvm/system_counter_offset_test.c create mode 100644 tools/testing/selftests/kvm/x86_64/kvm_clock_test.c -- 2.32.0.402.g57bb445576-goog _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm