linux-kernel - [RFC PATCH 0/6] x86/kvm: Virtual suspend time injection support

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Message-Id: <20210426090644.2218834-1-hikalium@chromium.org>
Date:   Mon, 26 Apr 2021 18:06:39 +0900
From:   Hikaru Nishida <hikalium@...omium.org>
To:     kvm@...r.kernel.org
Cc:     suleiman@...gle.com, Hikaru Nishida <hikalium@...omium.org>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        John Stultz <john.stultz@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [RFC PATCH 0/6] x86/kvm: Virtual suspend time injection support

Hi,

This patch series adds virtual suspend time injection support to KVM.

Before this change, if the host goes into suspended state while the
guest is running, the guest will experience a time jump after the host's
resume. This can confuse some services in the guest since they can't
detect if the system went into suspend or not by comparing
CLOCK_BOOTTIME and CLOCK_MONOTONIC.

To solve this problem, we wanted to add a way to adjust the guest clocks
without actually suspending the guests. However, there was no way to
modify a gap between CLOCK_BOOTTIME and CLOCK_MONOTONIC without actually
suspending the guests. Therefore, this series introduce a new struct
called kvm_host_suspend_time to share the suspend time between host and
guest and a mechanism to inject a suspend time to the guest while
keeping
monotonicity of the clocks.

Could you take a look and let me know how we can improve the patches if
they are doing something wrong?

Thanks,

Hikaru Nishida

Hikaru Nishida (6):
  x86/kvm: Reserve KVM_FEATURE_HOST_SUSPEND_TIME and
    MSR_KVM_HOST_SUSPEND_TIME
  x86/kvm: Add a struct and constants for virtual suspend time injection
  x86/kvm: Add CONFIG_KVM_VIRT_SUSPEND_TIMING
  x86/kvm: Add a host side support for virtual suspend time injection
  x86/kvm: Add CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
  x86/kvm: Add a guest side support for virtual suspend time injection

 Documentation/virt/kvm/cpuid.rst     |  3 +
 Documentation/virt/kvm/msr.rst       | 29 +++++++++
 arch/x86/Kconfig                     | 13 ++++
 arch/x86/include/asm/kvm_host.h      |  5 ++
 arch/x86/include/asm/kvm_para.h      |  9 +++
 arch/x86/include/uapi/asm/kvm_para.h |  6 ++
 arch/x86/kernel/kvmclock.c           | 25 ++++++++
 arch/x86/kvm/Kconfig                 | 13 ++++
 arch/x86/kvm/cpuid.c                 |  4 ++
 arch/x86/kvm/x86.c                   | 89 +++++++++++++++++++++++++++-
 include/linux/kvm_host.h             |  7 +++
 include/linux/timekeeper_internal.h  |  4 ++
 kernel/time/timekeeping.c            | 31 ++++++++++
 13 files changed, 237 insertions(+), 1 deletion(-)

-- 
2.31.1.498.g6c1eba8ee3d-goog