| Message ID | 20210426090644.2218834-1-hikalium@chromium.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | x86/kvm: Virtual suspend time injection support | expand |
On Mon, 2021-04-26 at 18:06 +0900, Hikaru Nishida wrote: > 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 > I haven't yet looked at that, but in my experience when I suspend the host with VMs running, after resume all my VMs complain something about TSC watchdog and stop using it. The TSC is stable/synchornized, but after resume it does reset to 0 on all CPUs. I use INVTSC flag for all my VMs. I haven't investigated this futher yet. Just my 0.2 cents. Best regards, Maxim Levitsky > > > 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(-) >
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(-)