Re: [PATCH v5 4/9] KVM-HV: KVM Steal time implementation
From: Glauber Costa
Date: Thu Jul 07 2011 - 13:08:59 EST
On 07/07/2011 07:51 AM, Marcelo Tosatti wrote:
On Mon, Jul 04, 2011 at 11:32:23AM -0400, Glauber Costa wrote:
To implement steal time, we need the hypervisor to pass the guest
information about how much time was spent running other processes
outside the VM, while the vcpu had meaningful work to do - halt
time does not count.
This information is acquired through the run_delay field of
delayacct/schedstats infrastructure, that counts time spent in a
runqueue but not running.
Steal time is a per-cpu information, so the traditional MSR-based
infrastructure is used. A new msr, KVM_MSR_STEAL_TIME, holds the
memory area address containing information about steal time
This patch contains the hypervisor part of the steal time infrasructure,
and can be backported independently of the guest portion.
Signed-off-by: Glauber Costa<glommer@xxxxxxxxxx>
CC: Rik van Riel<riel@xxxxxxxxxx>
CC: Jeremy Fitzhardinge<jeremy.fitzhardinge@xxxxxxxxxx>
CC: Peter Zijlstra<peterz@xxxxxxxxxxxxx>
CC: Avi Kivity<avi@xxxxxxxxxx>
CC: Anthony Liguori<aliguori@xxxxxxxxxx>
CC: Eric B Munson<emunson@xxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 8 +++++
arch/x86/include/asm/kvm_para.h | 4 +++
arch/x86/kvm/Kconfig | 1 +
arch/x86/kvm/x86.c | 56 ++++++++++++++++++++++++++++++++++++--
4 files changed, 66 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index da6bbee..9ba354d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -389,6 +389,14 @@ struct kvm_vcpu_arch {
unsigned int hw_tsc_khz;
unsigned int time_offset;
struct page *time_page;
+
+ struct {
+ u64 msr_val;
+ u64 last_steal;
+ struct gfn_to_hva_cache stime;
+ struct kvm_steal_time steal;
+ } st;
+
u64 last_guest_tsc;
u64 last_kernel_ns;
u64 last_tsc_nsec;
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 65f8bb9..c484ba8 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -45,6 +45,10 @@ struct kvm_steal_time {
__u32 pad[12];
};
+#define KVM_STEAL_ALIGNMENT_BITS 5
+#define KVM_STEAL_VALID_BITS ((-1ULL<< (KVM_STEAL_ALIGNMENT_BITS + 1)))
+#define KVM_STEAL_RESERVED_MASK (((1<< KVM_STEAL_ALIGNMENT_BITS) - 1 )<< 1)
+
#define KVM_MAX_MMU_OP_BATCH 32
#define KVM_ASYNC_PF_ENABLED (1<< 0)
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 50f6364..99c3f05 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -31,6 +31,7 @@ config KVM
select KVM_ASYNC_PF
select USER_RETURN_NOTIFIER
select KVM_MMIO
+ select TASK_DELAY_ACCT
---help---
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7167717..237bcdc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -808,12 +808,12 @@ EXPORT_SYMBOL_GPL(kvm_get_dr);
* kvm-specific. Those are put in the beginning of the list.
*/
-#define KVM_SAVE_MSRS_BEGIN 8
+#define KVM_SAVE_MSRS_BEGIN 9
static u32 msrs_to_save[] = {
MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
- HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN,
+ HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
MSR_STAR,
#ifdef CONFIG_X86_64
@@ -1491,6 +1491,27 @@ static void kvmclock_reset(struct kvm_vcpu *vcpu)
}
}
+static void record_steal_time(struct kvm_vcpu *vcpu)
+{
+ u64 delta;
+
+ if (!(vcpu->arch.st.msr_val& KVM_MSR_ENABLED))
+ return;
+
+ if (unlikely(kvm_read_guest_cached(vcpu->kvm,&vcpu->arch.st.stime,
+ &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
+ return;
The guest memory page is not pinned, sleeping via
__copy_from_user/to_user is not allowed in vcpu_load context. Either pin
it or use atomic acessors.
I do recognize the problem.
Avi, what's your take here?
+ case MSR_KVM_STEAL_TIME:
+ vcpu->arch.st.msr_val = data;
+
+ if (!(data& KVM_MSR_ENABLED)) {
+ break;
+ }
On failure below this point, msr_val should be cleared of KVM_MSR_ENABLED?
No, msr_val has to hold whatever the guest wrote into it.
We should probably use an independent variable here to indicate that we
failed to activate it.
+
+ if (unlikely(!sched_info_on()))
+ break;
+
+ if (data& KVM_STEAL_RESERVED_MASK)
+ return 1;
+
+ if (kvm_gfn_to_hva_cache_init(vcpu->kvm,&vcpu->arch.st.stime,
+ data& KVM_STEAL_VALID_BITS))
+ return 1;
+
+ vcpu->arch.st.last_steal = current->sched_info.run_delay;
+
+ record_steal_time(vcpu);
+ break;
+
--
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