[PATCH][v4] PV extension of HVM(hybrid) support in Xen

[PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Sheng Yang]

[-- Attachment #1: Type: Text/Plain, Size: 581 bytes --]

Hi Keir

Here is the latest (hybrid) patchset.

Change from v3:

1. Minor polish the patchset. Replace several specific 
is_hvm_pv_evtchn_domain() judgement.
2. Name changed...

Change from v2:

1. Change the name "hybrid" to "PV featured HVM", as well as flag and macro 
names.
2. Merge the hypercall page with HVM.
3. Clean up VIRQ delivery mechanism, fixing the lock issue.
4. Remove the reserved the region in E820(but another issue remains, I can't 
get location of grant table elegantly, as I described in Linux part patches)

Please review, thanks!

-- 
regards
Yang, Sheng

[-- Attachment #2: hybrid-xen.patch --]
[-- Type: text/x-patch, Size: 11691 bytes --]

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -682,7 +682,16 @@
 
     if ( is_hvm_vcpu(v) )
     {
+        unsigned long eip, cs;
+
         hvm_set_info_guest(v);
+
+        eip = c(user_regs.eip);
+        if (eip != 0) {
+            cs = eip >> 12 << 8;
+            hvm_vcpu_reset_state(v, cs, 0);
+            hvm_funcs.set_tsc_offset(v, 0);
+        }
         goto out;
     }
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2239,6 +2239,13 @@
     {
     case VCPUOP_register_runstate_memory_area:
     case VCPUOP_get_runstate_info:
+    /* For evtchn on HVM */
+    case VCPUOP_initialise:
+    case VCPUOP_up:
+    case VCPUOP_set_periodic_timer:
+    case VCPUOP_stop_periodic_timer:
+    case VCPUOP_set_singleshot_timer:
+    case VCPUOP_stop_singleshot_timer:
         rc = do_vcpu_op(cmd, vcpuid, arg);
         break;
     default:
@@ -2310,6 +2317,7 @@
     [ __HYPERVISOR_grant_table_op ] = (hvm_hypercall_t *)hvm_grant_table_op,
     [ __HYPERVISOR_vcpu_op ] = (hvm_hypercall_t *)hvm_vcpu_op,
     HYPERCALL(xen_version),
+    HYPERCALL(console_io),
     HYPERCALL(event_channel_op),
     HYPERCALL(sched_op),
     HYPERCALL(hvm_op)
@@ -3109,6 +3117,36 @@
         break;
     }
 
+    case HVMOP_enable_pv: {
+        struct xen_hvm_pv_type a;
+        struct domain *d;
+
+        if ( copy_from_guest(&a, arg, 1) )
+            return -EFAULT;
+
+        rc = rcu_lock_target_domain_by_id(a.domid, &d);
+        if ( rc != 0 )
+            return rc;
+
+        rc = -EINVAL;
+        if ( !is_hvm_domain(d) )
+            goto param_fail5;
+
+        rc = xsm_hvm_param(d, op);
+        if ( rc )
+            goto param_fail5;
+
+        if (a.flags & HVM_PV_EVTCHN) {
+            update_domain_wallclock_time(d);
+            hvm_funcs.set_tsc_offset(d->vcpu[0], 0);
+            d->hvm_pv_enabled |= XEN_HVM_PV_EVTCHN_ENABLED;
+            printk("HVM: PV featured evtchn enabled\n");
+        }
+param_fail5:
+        rcu_unlock_domain(d);
+        break;
+    }
+
     default:
     {
         gdprintk(XENLOG_WARNING, "Bad HVM op %ld.\n", op);
diff --git a/xen/arch/x86/hvm/irq.c b/xen/arch/x86/hvm/irq.c
--- a/xen/arch/x86/hvm/irq.c
+++ b/xen/arch/x86/hvm/irq.c
@@ -26,6 +26,32 @@
 #include <asm/hvm/domain.h>
 #include <asm/hvm/support.h>
 
+/* Must be called with hvm_domain->irq_lock hold */
+static void assert_irq(struct domain *d, unsigned ioapic_gsi, unsigned pic_irq)
+{
+    struct vcpu *v = d->vcpu[0];
+    int virq_pin = VIRQ_EMUL_PIN(pic_irq);
+
+    if ( v->virq_to_evtchn[virq_pin] != 0 )
+    {
+        send_guest_global_virq(d, virq_pin);
+        return;
+    }
+    vioapic_irq_positive_edge(d, ioapic_gsi);
+    vpic_irq_positive_edge(d, pic_irq);
+}
+
+/* Must be called with hvm_domain->irq_lock hold */
+static void deassert_irq(struct domain *d, unsigned isa_irq)
+{
+    struct vcpu *v = d->vcpu[0];
+    int virq_pin = VIRQ_EMUL_PIN(isa_irq);
+
+    if ( v->virq_to_evtchn[virq_pin] == 0 )
+        /* Not VIRQ drove */
+        vpic_irq_negative_edge(d, isa_irq);
+}
+
 static void __hvm_pci_intx_assert(
     struct domain *d, unsigned int device, unsigned int intx)
 {
@@ -45,10 +71,7 @@
     isa_irq = hvm_irq->pci_link.route[link];
     if ( (hvm_irq->pci_link_assert_count[link]++ == 0) && isa_irq &&
          (hvm_irq->gsi_assert_count[isa_irq]++ == 0) )
-    {
-        vioapic_irq_positive_edge(d, isa_irq);
-        vpic_irq_positive_edge(d, isa_irq);
-    }
+        assert_irq(d, isa_irq, isa_irq);
 }
 
 void hvm_pci_intx_assert(
@@ -77,7 +100,7 @@
     isa_irq = hvm_irq->pci_link.route[link];
     if ( (--hvm_irq->pci_link_assert_count[link] == 0) && isa_irq &&
          (--hvm_irq->gsi_assert_count[isa_irq] == 0) )
-        vpic_irq_negative_edge(d, isa_irq);
+        deassert_irq(d, isa_irq);
 }
 
 void hvm_pci_intx_deassert(
@@ -100,10 +123,7 @@
 
     if ( !__test_and_set_bit(isa_irq, &hvm_irq->isa_irq.i) &&
          (hvm_irq->gsi_assert_count[gsi]++ == 0) )
-    {
-        vioapic_irq_positive_edge(d, gsi);
-        vpic_irq_positive_edge(d, isa_irq);
-    }
+        assert_irq(d, gsi, isa_irq);
 
     spin_unlock(&d->arch.hvm_domain.irq_lock);
 }
@@ -120,7 +140,7 @@
 
     if ( __test_and_clear_bit(isa_irq, &hvm_irq->isa_irq.i) &&
          (--hvm_irq->gsi_assert_count[gsi] == 0) )
-        vpic_irq_negative_edge(d, isa_irq);
+        deassert_irq(d, isa_irq);
 
     spin_unlock(&d->arch.hvm_domain.irq_lock);
 }
@@ -185,16 +205,16 @@
 
 void hvm_assert_evtchn_irq(struct vcpu *v)
 {
-    if ( v->vcpu_id != 0 )
-        return;
-
     if ( unlikely(in_irq() || !local_irq_is_enabled()) )
     {
         tasklet_schedule(&v->arch.hvm_vcpu.assert_evtchn_irq_tasklet);
         return;
     }
 
-    hvm_set_callback_irq_level(v);
+    if (is_hvm_pv_evtchn_vcpu(v))
+        vcpu_kick(v);
+    else
+        hvm_set_callback_irq_level(v);
 }
 
 void hvm_set_pci_link_route(struct domain *d, u8 link, u8 isa_irq)
@@ -251,7 +271,7 @@
 
     via_type = (uint8_t)(via >> 56) + 1;
     if ( ((via_type == HVMIRQ_callback_gsi) && (via == 0)) ||
-         (via_type > HVMIRQ_callback_pci_intx) )
+         (via_type > HVMIRQ_callback_vector) )
         via_type = HVMIRQ_callback_none;
 
     spin_lock(&d->arch.hvm_domain.irq_lock);
@@ -297,6 +317,9 @@
         if ( hvm_irq->callback_via_asserted )
              __hvm_pci_intx_assert(d, pdev, pintx);
         break;
+    case HVMIRQ_callback_vector:
+        hvm_irq->callback_via.vector = (uint8_t)via;
+        break;
     default:
         break;
     }
@@ -312,6 +335,10 @@
     case HVMIRQ_callback_pci_intx:
         printk("PCI INTx Dev 0x%02x Int%c\n", pdev, 'A' + pintx);
         break;
+    case HVMIRQ_callback_vector:
+        printk("Set HVMIRQ_callback_vector to %u\n",
+               hvm_irq->callback_via.vector);
+        break;
     default:
         printk("None\n");
         break;
@@ -322,6 +349,10 @@
 {
     struct hvm_domain *plat = &v->domain->arch.hvm_domain;
     int vector;
+
+    if (plat->irq.callback_via_type == HVMIRQ_callback_vector &&
+            vcpu_info(v, evtchn_upcall_pending))
+        return hvm_intack_vector(plat->irq.callback_via.vector);
 
     if ( unlikely(v->nmi_pending) )
         return hvm_intack_nmi;
@@ -363,6 +394,8 @@
     case hvm_intsrc_lapic:
         if ( !vlapic_ack_pending_irq(v, intack.vector) )
             intack = hvm_intack_none;
+        break;
+    case hvm_intsrc_vector:
         break;
     default:
         intack = hvm_intack_none;
diff --git a/xen/arch/x86/hvm/vmx/intr.c b/xen/arch/x86/hvm/vmx/intr.c
--- a/xen/arch/x86/hvm/vmx/intr.c
+++ b/xen/arch/x86/hvm/vmx/intr.c
@@ -164,7 +164,8 @@
     {
         HVMTRACE_2D(INJ_VIRQ, intack.vector, /*fake=*/ 0);
         vmx_inject_extint(intack.vector);
-        pt_intr_post(v, intack);
+        if (intack.source != hvm_intsrc_vector)
+             pt_intr_post(v, intack);
     }
 
     /* Is there another IRQ to queue up behind this one? */
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -686,6 +686,7 @@
     struct domain *d = current->domain;
     /* Optionally shift out of the way of Viridian architectural leaves. */
     uint32_t base = is_viridian_domain(d) ? 0x40000100 : 0x40000000;
+    unsigned int tmp_eax, tmp_ebx, tmp_ecx, tmp_edx;
 
     idx -= base;
     if ( idx > 3 ) 
@@ -716,6 +717,14 @@
         *edx = 0;          /* Features 2 */
         if ( !is_hvm_vcpu(current) )
             *ecx |= XEN_CPUID_FEAT1_MMU_PT_UPDATE_PRESERVE_AD;
+
+        /* Check if additional feature specified, e.g. Hybrid */
+        if ( !is_viridian_domain(d) ) {
+            domain_cpuid(d, 0x40000002, 0,
+                         &tmp_eax, &tmp_ebx, &tmp_ecx, &tmp_edx);
+            if (tmp_edx != 0)
+                *edx = tmp_edx & XEN_CPUID_FEAT2_MASK;
+        }
         break;
 
     case 3:
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -33,7 +33,8 @@
     hvm_intsrc_pic,
     hvm_intsrc_lapic,
     hvm_intsrc_nmi,
-    hvm_intsrc_mce
+    hvm_intsrc_mce,
+    hvm_intsrc_vector,
 };
 struct hvm_intack {
     uint8_t source; /* enum hvm_intsrc */
@@ -44,6 +45,7 @@
 #define hvm_intack_lapic(vec) ( (struct hvm_intack) { hvm_intsrc_lapic, vec } )
 #define hvm_intack_nmi        ( (struct hvm_intack) { hvm_intsrc_nmi,   2 } )
 #define hvm_intack_mce        ( (struct hvm_intack) { hvm_intsrc_mce,   18 } )
+#define hvm_intack_vector(vec)( (struct hvm_intack) { hvm_intsrc_vector, vec } )
 enum hvm_intblk {
     hvm_intblk_none,      /* not blocked (deliverable) */
     hvm_intblk_shadow,    /* MOV-SS or STI shadow */
diff --git a/xen/include/asm-x86/hvm/irq.h b/xen/include/asm-x86/hvm/irq.h
--- a/xen/include/asm-x86/hvm/irq.h
+++ b/xen/include/asm-x86/hvm/irq.h
@@ -54,12 +54,14 @@
         enum {
             HVMIRQ_callback_none,
             HVMIRQ_callback_gsi,
-            HVMIRQ_callback_pci_intx
+            HVMIRQ_callback_pci_intx,
+            HVMIRQ_callback_vector,
         } callback_via_type;
     };
     union {
         uint32_t gsi;
         struct { uint8_t dev, intx; } pci;
+        uint32_t vector;
     } callback_via;
 
     /* Number of INTx wires asserting each PCI-ISA link. */
diff --git a/xen/include/public/arch-x86/cpuid.h b/xen/include/public/arch-x86/cpuid.h
--- a/xen/include/public/arch-x86/cpuid.h
+++ b/xen/include/public/arch-x86/cpuid.h
@@ -65,4 +65,11 @@
 #define _XEN_CPUID_FEAT1_MMU_PT_UPDATE_PRESERVE_AD 0
 #define XEN_CPUID_FEAT1_MMU_PT_UPDATE_PRESERVE_AD  (1u<<0)
 
+/* Mask unsupported CPUID specified by user */
+#define XEN_CPUID_FEAT2_MASK 0x3ul
+#define _XEN_CPUID_FEAT2_HVM_PV 0
+#define XEN_CPUID_FEAT2_HVM_PV (1u<<0)
+#define _XEN_CPUID_FEAT2_HVM_PV_EVTCHN 1
+#define XEN_CPUID_FEAT2_HVM_PV_EVTCHN (1u<<1)
+
 #endif /* __XEN_PUBLIC_ARCH_X86_CPUID_H__ */
diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
--- a/xen/include/public/hvm/hvm_op.h
+++ b/xen/include/public/hvm/hvm_op.h
@@ -127,6 +127,12 @@
 typedef struct xen_hvm_set_mem_type xen_hvm_set_mem_type_t;
 DEFINE_XEN_GUEST_HANDLE(xen_hvm_set_mem_type_t);
 
+#define HVMOP_enable_pv 9
+struct xen_hvm_pv_type {
+    domid_t domid;
+    uint32_t flags;
+#define HVM_PV_EVTCHN (1ull<<1)
+};
 
 #endif /* defined(__XEN__) || defined(__XEN_TOOLS__) */
 
diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -158,7 +158,12 @@
 #define VIRQ_ARCH_6    22
 #define VIRQ_ARCH_7    23
 
-#define NR_VIRQS       24
+#define VIRQ_EMUL_PIN_START 24
+#define VIRQ_EMUL_PIN_END 39
+#define VIRQ_EMUL_PIN_NUM 16
+#define VIRQ_EMUL_PIN(x) (VIRQ_EMUL_PIN_START + x)
+
+#define NR_VIRQS       40
 
 /*
  * HYPERVISOR_mmu_update(reqs, count, pdone, foreigndom)
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -309,6 +309,9 @@
 
     /* Memory paging support */
     struct mem_event_domain mem_event;
+
+#define XEN_HVM_PV_EVTCHN_ENABLED   (1u << 1)
+    uint64_t hvm_pv_enabled;
 };
 
 struct domain_setup_info
@@ -595,6 +598,9 @@
 #define is_hvm_vcpu(v)   (is_hvm_domain(v->domain))
 #define need_iommu(d)    ((d)->need_iommu)
 
+#define is_hvm_pv_evtchn_domain(d) ((d)->hvm_pv_enabled & XEN_HVM_PV_EVTCHN_ENABLED)
+#define is_hvm_pv_evtchn_vcpu(v) (is_hvm_pv_evtchn_domain(v->domain))
+
 void set_vcpu_migration_delay(unsigned int delay);
 unsigned int get_vcpu_migration_delay(void);
 

[-- Attachment #3: Type: text/plain, Size: 138 bytes --]

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Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Keir Fraser]

If the Linux guys are happy with the interface then this looks fine to me
and it can go in as soon as 4.0 is out the door.

 -- Keir

On 01/03/2010 09:43, "Sheng Yang" <sheng@linux.intel.com> wrote:

> Hi Keir
> 
> Here is the latest (hybrid) patchset.
> 
> Change from v3:
> 
> 1. Minor polish the patchset. Replace several specific
> is_hvm_pv_evtchn_domain() judgement.
> 2. Name changed...
> 
> Change from v2:
> 
> 1. Change the name "hybrid" to "PV featured HVM", as well as flag and macro
> names.
> 2. Merge the hypercall page with HVM.
> 3. Clean up VIRQ delivery mechanism, fixing the lock issue.
> 4. Remove the reserved the region in E820(but another issue remains, I can't
> get location of grant table elegantly, as I described in Linux part patches)
> 
> Please review, thanks!

Re: Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Stefano Stabellini]

On Mon, 1 Mar 2010, Keir Fraser wrote:
> If the Linux guys are happy with the interface then this looks fine to me
> and it can go in as soon as 4.0 is out the door.
> 

Could you please wait for a week or two before applying this patch
series?
I am working on a different approach on interrupt remapping, basically
a replacement for patch 5, it also requires some modifications on the
xen side.
The basic idea is that from the kernel perspective asking event channel
delivery for real physical interrupts or event channel delivery for
emulated interrupts should be same thing. The code to do the former
is basically xen_setup_pirqs() in the pvops tree. I got it to work for
the first time a couple of days ago but it still needs to be polished
before I can send it to the list.

Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Tim Deegan]

At 09:43 +0000 on 01 Mar (1267436621), Sheng Yang wrote:
> @@ -3109,6 +3117,36 @@
>          break;
>      }
>  
> +    case HVMOP_enable_pv: {

Why does this have to be explicitly enabled?  Can't you just notice that
a domain is using the evtchnop hypercalls?

> +        struct xen_hvm_pv_type a;
> +        struct domain *d;
> +
> +        if ( copy_from_guest(&a, arg, 1) )
> +            return -EFAULT;
> +
> +        rc = rcu_lock_target_domain_by_id(a.domid, &d);

Domains do this to each other?  It looks like it has surprising side-effects.

> +        if ( rc != 0 )
> +            return rc;
> +
> +        rc = -EINVAL;
> +        if ( !is_hvm_domain(d) )
> +            goto param_fail5;
> +
> +        rc = xsm_hvm_param(d, op);
> +        if ( rc )
> +            goto param_fail5;
> +
> +        if (a.flags & HVM_PV_EVTCHN) {
> +            update_domain_wallclock_time(d);
> +            hvm_funcs.set_tsc_offset(d->vcpu[0], 0);

Only vcpu 0?  Doesn't this do horrible things to timekeeping in the guest?

> +            d->hvm_pv_enabled |= XEN_HVM_PV_EVTCHN_ENABLED;
> +            printk("HVM: PV featured evtchn enabled\n");

Please remove your debugging printks.

> +        }
> +param_fail5:
> +        rcu_unlock_domain(d);
> +        break;
> +    }
> +
>      default:
>      {
>          gdprintk(XENLOG_WARNING, "Bad HVM op %ld.\n", op);

Tim.

-- 
Tim Deegan <Tim.Deegan@citrix.com>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Sheng Yang]

On Monday 01 March 2010 18:21:27 Tim Deegan wrote:
> At 09:43 +0000 on 01 Mar (1267436621), Sheng Yang wrote:
> > @@ -3109,6 +3117,36 @@
> >          break;
> >      }
> >
> > +    case HVMOP_enable_pv: {
> 
> Why does this have to be explicitly enabled?  Can't you just notice that
> a domain is using the evtchnop hypercalls?

The issue is pv timer. It assumed the tsc start from 0, which is different 
from HVM. So I'd like to give it a explicit call here. Otherwise it can be 
hooked in evtchn binding, but I don't think that's clear...
 
> > +        struct xen_hvm_pv_type a;
> > +        struct domain *d;
> > +
> > +        if ( copy_from_guest(&a, arg, 1) )
> > +            return -EFAULT;
> > +
> > +        rc = rcu_lock_target_domain_by_id(a.domid, &d);
> 
> Domains do this to each other?  It looks like it has surprising
>  side-effects.

Should not allowed... I think a.domid should always be the current domain. 
Replace it with DOMID_SELF?
 
> > +        if ( rc != 0 )
> > +            return rc;
> > +
> > +        rc = -EINVAL;
> > +        if ( !is_hvm_domain(d) )
> > +            goto param_fail5;
> > +
> > +        rc = xsm_hvm_param(d, op);
> > +        if ( rc )
> > +            goto param_fail5;
> > +
> > +        if (a.flags & HVM_PV_EVTCHN) {
> > +            update_domain_wallclock_time(d);
> > +            hvm_funcs.set_tsc_offset(d->vcpu[0], 0);
> 
> Only vcpu 0?  Doesn't this do horrible things to timekeeping in the guest?

The other vcpus are initialized when it is brought up. TSC started from 0 is a 
fundamental assumption for pv clock in Linux... 
> 
> > +            d->hvm_pv_enabled |= XEN_HVM_PV_EVTCHN_ENABLED;
> > +            printk("HVM: PV featured evtchn enabled\n");
> 
> Please remove your debugging printks.

OK...

-- 
regards
Yang, Sheng

> 
> > +        }
> > +param_fail5:
> > +        rcu_unlock_domain(d);
> > +        break;
> > +    }
> > +
> >      default:
> >      {
> >          gdprintk(XENLOG_WARNING, "Bad HVM op %ld.\n", op);
> 
> Tim.
> 

Re: Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Jeremy Fitzhardinge]

On 03/01/2010 03:40 AM, Sheng Yang wrote:
> The issue is pv timer. It assumed the tsc start from 0, which is different
> from HVM. So I'd like to give it a explicit call here. Otherwise it can be
> hooked in evtchn binding, but I don't think that's clear...
>
>    
[...]
>> Only vcpu 0?  Doesn't this do horrible things to timekeeping in the guest?
>>      
> The other vcpus are initialized when it is brought up. TSC started from 0 is a
> fundamental assumption for pv clock in Linux...
>    

Could you expand on this?  Do you mean in the pvops Xen time code?  What 
do you mean?

     J

Re: Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Sheng Yang]

On Tuesday 02 March 2010 09:49:55 Jeremy Fitzhardinge wrote:
> On 03/01/2010 03:40 AM, Sheng Yang wrote:
> > The issue is pv timer. It assumed the tsc start from 0, which is
> > different from HVM. So I'd like to give it a explicit call here.
> > Otherwise it can be hooked in evtchn binding, but I don't think that's
> > clear...
> 
> [...]
> 
> >> Only vcpu 0?  Doesn't this do horrible things to timekeeping in the
> >> guest?
> >
> > The other vcpus are initialized when it is brought up. TSC started from 0
> > is a fundamental assumption for pv clock in Linux...
> 
> Could you expand on this?  Do you mean in the pvops Xen time code?  What
> do you mean?
> 

The function pvclock_get_nsec_offset() in Linux kernel have this:

>static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
>{
>        u64 delta = native_read_tsc() - shadow->tsc_timestamp;
>        return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow-
>tsc_shift);
>}

tsc_timestamp take the vcpu beginning at 0, so that's the assumption. So I 
adjusted guest TSC(the return value of native_read_tsc()) to satisfy this 
assumption. 

-- 
regards
Yang, Sheng

Re: Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Jeremy Fitzhardinge]

On 03/01/2010 07:36 PM, Sheng Yang wrote:
>> static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
>> {
>>         u64 delta = native_read_tsc() - shadow->tsc_timestamp;
>>         return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow-
>> tsc_shift);
>> }
>>      
> tsc_timestamp take the vcpu beginning at 0, so that's the assumption.

Why would it be 0?  Xen sets tsc_timestamp to the current tsc when it 
updates the time parameters, which is whenever the vcpu is scheduled on 
a pcpu (and other times).  There's no expectation that the tsc starts 
from 0, since that won't ever be the case.

     J

Re: Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Sheng Yang]

On Tuesday 02 March 2010 12:39:34 Jeremy Fitzhardinge wrote:
> On 03/01/2010 07:36 PM, Sheng Yang wrote:
> >> static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
> >> {
> >>         u64 delta = native_read_tsc() - shadow->tsc_timestamp;
> >>         return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow-
> >> tsc_shift);
> >> }
> >
> > tsc_timestamp take the vcpu beginning at 0, so that's the assumption.
> 
> Why would it be 0?  Xen sets tsc_timestamp to the current tsc when it
> updates the time parameters, which is whenever the vcpu is scheduled on
> a pcpu (and other times).  There's no expectation that the tsc starts
> from 0, since that won't ever be the case.
> 
Sorry, I misunderstood. HVM assume it start from 0... PV is following the 
native. We set the offset to 0, so that PV tsc is the same as native.

-- 
regards
Yang, Sheng

Re: Re: [PATCH][v4] PV extension of HVM(hybrid) support in Xen

[Jeremy Fitzhardinge]

On 03/01/2010 09:04 PM, Sheng Yang wrote:
> Sorry, I misunderstood. HVM assume it start from 0... PV is following the
> native. We set the offset to 0, so that PV tsc is the same as native.
>    

OK, I see.

     J