[PATCH 0/2] provide disable clock functionality.

[PATCH 0/2] provide disable clock functionality.

[Glauber Costa]

Avi,

Hope this is better



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[PATCH 1/2] [PATCH] use per cpu variables instead of a vector

[Glauber Costa]

replace hv_clock vector in kvmclock with a percpu variable
that is cacheline aligned.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
---
 arch/x86/kernel/kvmclock.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 9c4a0f4..7c481a3 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -20,6 +20,7 @@ #include <linux/clocksource.h>
 #include <linux/kvm_para.h>
 #include <asm/arch_hooks.h>
 #include <asm/msr.h>
+#include <linux/percpu.h>
 
 #define KVM_SCALE 22
 
@@ -33,8 +34,8 @@ static int parse_no_kvmclock(char *arg)
 early_param("no-kvmclock", parse_no_kvmclock);
 
 /* The hypervisor will put information about time periodically here */
-static struct kvm_vcpu_time_info hv_clock[NR_CPUS];
-#define get_clock(cpu, field) hv_clock[cpu].field
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct kvm_vcpu_time_info, hv_clock);
+#define get_clock(cpu, field) per_cpu(hv_clock, cpu).field
 
 static inline u64 kvm_get_delta(u64 last_tsc)
 {
@@ -124,8 +125,8 @@ static int kvm_register_clock(void)
 {
 	int cpu = smp_processor_id();
 	int low, high;
-	low = (int)__pa(&hv_clock[cpu]);
-	high = ((u64)__pa(&hv_clock[cpu]) >> 32);
+	low = (int)__pa(&per_cpu(hv_clock, cpu));
+	high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
 
 	return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
 }
-- 
1.4.2


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[PATCH 2/2] [PATCH] disable kvm clock unless addr's LSB is set.

[Glauber Costa]

Use LSB of the address passed through the msr to enable/disable
the clock. Setting it to 1 enables it, setting it to 0 disables it.

As the guest data structures are aligned anyway, this
won't be a problem, as this bit is free.

Guest is changed accordingly

Signed-off-by: Glauber Costa <gcosta@redhat.com>
---
 arch/x86/kernel/kvmclock.c |    2 +-
 arch/x86/kvm/x86.c         |    9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 7c481a3..f654a12 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -125,7 +125,7 @@ static int kvm_register_clock(void)
 {
 	int cpu = smp_processor_id();
 	int low, high;
-	low = (int)__pa(&per_cpu(hv_clock, cpu));
+	low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
 	high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
 
 	return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6abd784..64beff6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -591,8 +591,15 @@ int kvm_set_msr_common(struct kvm_vcpu *
 		if (vcpu->arch.time_page)
 			kvm_release_page_dirty(vcpu->arch.time_page);
 
+		/* we verify if the enable bit is set... */
+		if (!(data & 1)) {
+			vcpu->arch.time = NULL;
+			break;
+		}
+
 		vcpu->arch.time = data & PAGE_MASK;
-		vcpu->arch.time_offset = data & ~PAGE_MASK;
+		/* ...but clean it before doing the actual write */
+		vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);
 
 		vcpu->arch.hv_clock.tsc_to_system_mul =
 					clocksource_khz2mult(tsc_khz, 22);
-- 
1.4.2


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Re: [PATCH 2/2] [PATCH] disable kvm clock unless addr's LSB is set.

[Yang, Sheng]

On Thursday 06 March 2008 22:45:44 Glauber Costa wrote:
> Use LSB of the address passed through the msr to enable/disable
> the clock. Setting it to 1 enables it, setting it to 0 disables it.
>
> As the guest data structures are aligned anyway, this
> won't be a problem, as this bit is free.
>
> Guest is changed accordingly
>
> Signed-off-by: Glauber Costa <gcosta@redhat.com>
> ---
>  arch/x86/kernel/kvmclock.c |    2 +-
>  arch/x86/kvm/x86.c         |    9 ++++++++-
>  2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index 7c481a3..f654a12 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -125,7 +125,7 @@ static int kvm_register_clock(void)
>  {
>  	int cpu = smp_processor_id();
>  	int low, high;
> -	low = (int)__pa(&per_cpu(hv_clock, cpu));
> +	low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
>  	high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
>
>  	return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6abd784..64beff6 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -591,8 +591,15 @@ int kvm_set_msr_common(struct kvm_vcpu *
>  		if (vcpu->arch.time_page)
>  			kvm_release_page_dirty(vcpu->arch.time_page);
>
> +		/* we verify if the enable bit is set... */
> +		if (!(data & 1)) {
> +			vcpu->arch.time = NULL;

This line made compiler complaining...

Thanks
Yang, Sheng

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Re: [PATCH 0/2] provide disable clock functionality.

[Avi Kivity]

Glauber Costa wrote:
> Avi,
>
> Hope this is better
>   

Applied, thanks.

-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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