Messages in this thread | | | Date | Tue, 01 Nov 2011 14:34:27 -0500 | From | Anthony Liguori <> | Subject | Re: [PATCH 6/6 V2] Add age out of guest paused flag |
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On 10/31/2011 03:07 PM, Eric B Munson wrote: > The KVM_GUEST_PAUSED flag will prevent a guest from compaining about a soft > lockup but it can mask real soft lockups if the flag isn't cleared when it is > no longer relevant. This patch adds a kvm ioctl that the hypervisor will use > when it resumes a guest to start a timer for aging out the flag. The time out > will be specified by the hypervisor in the ioctl call. > > Signed-off-by: Eric B Munson<emunson@mgebm.net>
Why not have the guest clear the flag when it acknowledges it?
The hypervisor would unconditionally set the bit, and the guest would do a testandclear to check if the bit is set. I think that avoids the whole aging business.
Regards,
Anthony Liguori
> --- > Cahnges from V1: > Add host functions for flag management to arch/x86/kvm/x86.c instead of > kvmclock.c > > arch/x86/include/asm/pvclock.h | 2 ++ > arch/x86/kvm/x86.c | 32 ++++++++++++++++++++++++++++++++ > include/linux/kvm.h | 2 ++ > include/linux/kvm_host.h | 2 ++ > 4 files changed, 38 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h > index 9312814..e8460b9 100644 > --- a/arch/x86/include/asm/pvclock.h > +++ b/arch/x86/include/asm/pvclock.h > @@ -18,6 +18,8 @@ void kvm_set_host_stopped(struct kvm_vcpu *vcpu); > > bool kvm_check_and_clear_host_stopped(int cpu); > > +void kvm_clear_guest_paused(struct kvm_vcpu *vcpu, unsigned int length); > + > /* > * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction, > * yielding a 64-bit result. > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 592ac3b..fb0132a 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -46,6 +46,7 @@ > #include<linux/hash.h> > #include<linux/pci.h> > #include<trace/events/kvm.h> > +#include<linux/timer.h> > > #define CREATE_TRACE_POINTS > #include "trace.h" > @@ -3300,6 +3301,15 @@ long kvm_arch_vcpu_ioctl(struct file *filp, > kvm_set_host_stopped(vcpu); > break; > } > + case KVM_CLEAR_GUEST_PAUSED: { > + unsigned int length; > + r = -EFAULT; > + if (copy_from_user(&length, argp, sizeof length)) > + goto out; > + r = 0; > + kvm_clear_guest_paused(vcpu, length); > + break; > + } > default: > r = -EINVAL; > } > @@ -6133,6 +6143,28 @@ void kvm_set_host_stopped(struct kvm_vcpu *vcpu) > } > EXPORT_SYMBOL_GPL(kvm_set_host_stopped); > > +static void kvm_timer_clear_guest_paused(unsigned long vcpu_addr) > +{ > + struct kvm_vcpu *vcpu = (struct kvm_vcpu *)vcpu_addr; > + struct pvclock_vcpu_time_info *src =&vcpu->arch.hv_clock; > + src->flags = src->flags& (~PVCLOCK_GUEST_STOPPED); > +} > + > +/* > + * Host has resumed the guest, we need to clear the guest paused flag so we > + * don't mask any real soft lockups. > + */ > +void kvm_clear_guest_paused(struct kvm_vcpu *vcpu, unsigned int length) > +{ > + if (!timer_pending(&vcpu->flag_timer)) > + setup_timer(&vcpu->flag_timer, > + kvm_timer_clear_guest_paused, > + (unsigned long)vcpu); > + mod_timer(&vcpu->flag_timer, > + jiffies + (length * HZ)); > +} > +EXPORT_SYMBOL_GPL(kvm_clear_guest_paused); > + > int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, > struct kvm_sregs *sregs) > { > diff --git a/include/linux/kvm.h b/include/linux/kvm.h > index 87cab0d..bd9724c 100644 > --- a/include/linux/kvm.h > +++ b/include/linux/kvm.h > @@ -765,6 +765,8 @@ struct kvm_clock_data { > #define KVM_ALLOCATE_RMA _IOR(KVMIO, 0xa9, struct kvm_allocate_rma) > /* VM is being stopped by host */ > #define KVM_GUEST_PAUSED _IO(KVMIO, 0xaa) > +/* Start the timer to clear the paused flag */ > +#define KVM_CLEAR_GUEST_PAUSED _IO(KVMIO, 0xab) > > #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1<< 0) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index d526231..043af4d 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -19,6 +19,7 @@ > #include<linux/slab.h> > #include<linux/rcupdate.h> > #include<linux/ratelimit.h> > +#include<linux/timer.h> > #include<asm/signal.h> > > #include<linux/kvm.h> > @@ -154,6 +155,7 @@ struct kvm_vcpu { > #endif > > struct kvm_vcpu_arch arch; > + struct timer_list flag_timer; > }; > > static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
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