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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2/2] x86/HVM: Use fixed TSC value when saving or restoring domain
When a domain is saved each VCPU's TSC value needs to be preserved. To get it we
use hvm_get_guest_tsc(). This routine (either itself or via get_s_time() which
it may call) calculates VCPU's TSC based on current host's TSC value (by doing a
rdtscll()). Since this is performed for each VCPU separately we end up with
un-synchronized TSCs.
Similarly, during a restore each VCPU is assigned its TSC based on host's
current
tick, causing virtual TSCs to diverge further.
With this, we can easily get into situation where a guest may see time going
backwards.
Instead of reading new TSC value for each VCPU when saving/restoring it we
should
use the same value across all VCPUs.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
xen/arch/x86/hvm/hvm.c | 18 ++++++++++++------
xen/arch/x86/hvm/save.c | 36 ++++++++++++++++++++++++++----------
xen/arch/x86/hvm/svm/svm.c | 4 ++--
xen/arch/x86/hvm/vmx/vmx.c | 4 ++--
xen/arch/x86/hvm/vpt.c | 16 ++++++++++------
xen/arch/x86/time.c | 7 +++++--
xen/common/hvm/save.c | 5 +++++
xen/include/asm-x86/domain.h | 2 ++
xen/include/asm-x86/hvm/hvm.h | 9 ++++++---
xen/include/xen/hvm/save.h | 2 ++
xen/include/xen/time.h | 3 ++-
11 files changed, 74 insertions(+), 32 deletions(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index ae24211..98de16a 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -248,19 +248,22 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
return 1;
}
-void hvm_set_guest_tsc(struct vcpu *v, u64 guest_tsc)
+void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
{
uint64_t tsc;
uint64_t delta_tsc;
if ( v->domain->arch.vtsc )
{
- tsc = hvm_get_guest_time(v);
+ tsc = hvm_get_guest_time_fixed(v, at_tsc);
tsc = gtime_to_gtsc(v->domain, tsc);
}
else
{
- rdtscll(tsc);
+ if ( at_tsc )
+ tsc = at_tsc;
+ else
+ rdtscll(tsc);
}
delta_tsc = guest_tsc - tsc;
@@ -279,19 +282,22 @@ void hvm_set_guest_tsc_adjust(struct vcpu *v, u64
tsc_adjust)
v->arch.hvm_vcpu.msr_tsc_adjust = tsc_adjust;
}
-u64 hvm_get_guest_tsc(struct vcpu *v)
+u64 hvm_get_guest_tsc_fixed(struct vcpu *v, uint64_t at_tsc)
{
uint64_t tsc;
if ( v->domain->arch.vtsc )
{
- tsc = hvm_get_guest_time(v);
+ tsc = hvm_get_guest_time_fixed(v, at_tsc);
tsc = gtime_to_gtsc(v->domain, tsc);
v->domain->arch.vtsc_kerncount++;
}
else
{
- rdtscll(tsc);
+ if ( at_tsc )
+ tsc = at_tsc;
+ else
+ rdtscll(tsc);
}
return tsc + v->arch.hvm_vcpu.cache_tsc_offset;
diff --git a/xen/arch/x86/hvm/save.c b/xen/arch/x86/hvm/save.c
index 066fdb2..6b0767e 100644
--- a/xen/arch/x86/hvm/save.c
+++ b/xen/arch/x86/hvm/save.c
@@ -24,7 +24,7 @@
#include <asm/hvm/support.h>
#include <public/hvm/save.h>
-void arch_hvm_save(struct domain *d, struct hvm_save_header *hdr)
+void arch_hvm_save(struct domain *dom, struct hvm_save_header *hdr)
{
uint32_t eax, ebx, ecx, edx;
@@ -33,24 +33,32 @@ void arch_hvm_save(struct domain *d, struct hvm_save_header
*hdr)
hdr->cpuid = eax;
/* Save guest's preferred TSC. */
- hdr->gtsc_khz = d->arch.tsc_khz;
+ hdr->gtsc_khz = dom->arch.tsc_khz;
+
+ /* Time when saving started */
+ rdtscll(dom->arch.chkpt_tsc);
+}
+
+void arch_hvm_save_done(struct domain *dom)
+{
+ dom->arch.chkpt_tsc = 0;
}
-int arch_hvm_load(struct domain *d, struct hvm_save_header *hdr)
+int arch_hvm_load(struct domain *dom, struct hvm_save_header *hdr)
{
uint32_t eax, ebx, ecx, edx;
if ( hdr->magic != HVM_FILE_MAGIC )
{
printk(XENLOG_G_ERR "HVM%d restore: bad magic number %#"PRIx32"\n",
- d->domain_id, hdr->magic);
+ dom->domain_id, hdr->magic);
return -1;
}
if ( hdr->version != HVM_FILE_VERSION )
{
printk(XENLOG_G_ERR "HVM%d restore: unsupported version %u\n",
- d->domain_id, hdr->version);
+ dom->domain_id, hdr->version);
return -1;
}
@@ -59,20 +67,28 @@ int arch_hvm_load(struct domain *d, struct hvm_save_header
*hdr)
if ( (hdr->cpuid & ~0x0fUL) != (eax & ~0x0fUL) )
printk(XENLOG_G_INFO "HVM%d restore: VM saved on one CPU "
"(%#"PRIx32") and restored on another (%#"PRIx32").\n",
- d->domain_id, hdr->cpuid, eax);
+ dom->domain_id, hdr->cpuid, eax);
/* Restore guest's preferred TSC frequency. */
if ( hdr->gtsc_khz )
- d->arch.tsc_khz = hdr->gtsc_khz;
- if ( d->arch.vtsc )
- hvm_set_rdtsc_exiting(d, 1);
+ dom->arch.tsc_khz = hdr->gtsc_khz;
+ if ( dom->arch.vtsc )
+ hvm_set_rdtsc_exiting(dom, 1);
+
+ /* Time when restore started */
+ rdtscll(dom->arch.chkpt_tsc);
/* VGA state is not saved/restored, so we nobble the cache. */
- d->arch.hvm_domain.stdvga.cache = 0;
+ dom->arch.hvm_domain.stdvga.cache = 0;
return 0;
}
+void arch_hvm_load_done(struct domain *dom)
+{
+ dom->arch.chkpt_tsc = 0;
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 4fd5376..7aa55c3 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -318,7 +318,7 @@ static void svm_save_cpu_state(struct vcpu *v, struct
hvm_hw_cpu *data)
data->msr_efer = v->arch.hvm_vcpu.guest_efer;
data->msr_flags = -1ULL;
- data->tsc = hvm_get_guest_tsc(v);
+ data->tsc = hvm_get_guest_tsc_fixed(v, v->domain->arch.chkpt_tsc);
}
@@ -334,7 +334,7 @@ static void svm_load_cpu_state(struct vcpu *v, struct
hvm_hw_cpu *data)
v->arch.hvm_vcpu.guest_efer = data->msr_efer;
svm_update_guest_efer(v);
- hvm_set_guest_tsc(v, data->tsc);
+ hvm_set_guest_tsc_fixed(v, data->tsc, v->domain->arch.chkpt_tsc);
}
static void svm_save_vmcb_ctxt(struct vcpu *v, struct hvm_hw_cpu *ctxt)
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 8395e86..f10d34c 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -540,7 +540,7 @@ static void vmx_save_cpu_state(struct vcpu *v, struct
hvm_hw_cpu *data)
data->msr_star = guest_state->msrs[VMX_INDEX_MSR_STAR];
data->msr_syscall_mask = guest_state->msrs[VMX_INDEX_MSR_SYSCALL_MASK];
- data->tsc = hvm_get_guest_tsc(v);
+ data->tsc = hvm_get_guest_tsc_fixed(v, v->domain->arch.chkpt_tsc);
}
static void vmx_load_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data)
@@ -556,7 +556,7 @@ static void vmx_load_cpu_state(struct vcpu *v, struct
hvm_hw_cpu *data)
v->arch.hvm_vmx.cstar = data->msr_cstar;
v->arch.hvm_vmx.shadow_gs = data->shadow_gs;
- hvm_set_guest_tsc(v, data->tsc);
+ hvm_set_guest_tsc_fixed(v, data->tsc, v->domain->arch.chkpt_tsc);
}
diff --git a/xen/arch/x86/hvm/vpt.c b/xen/arch/x86/hvm/vpt.c
index f7af688..38541cf 100644
--- a/xen/arch/x86/hvm/vpt.c
+++ b/xen/arch/x86/hvm/vpt.c
@@ -36,7 +36,7 @@ void hvm_init_guest_time(struct domain *d)
pl->last_guest_time = 0;
}
-u64 hvm_get_guest_time(struct vcpu *v)
+u64 hvm_get_guest_time_fixed(struct vcpu *v, u64 at_tsc)
{
struct pl_time *pl = &v->domain->arch.hvm_domain.pl_time;
u64 now;
@@ -45,11 +45,15 @@ u64 hvm_get_guest_time(struct vcpu *v)
ASSERT(is_hvm_vcpu(v));
spin_lock(&pl->pl_time_lock);
- now = get_s_time() + pl->stime_offset;
- if ( (int64_t)(now - pl->last_guest_time) > 0 )
- pl->last_guest_time = now;
- else
- now = ++pl->last_guest_time;
+ now = get_s_time_fixed(at_tsc) + pl->stime_offset;
+
+ if ( !at_tsc )
+ {
+ if ( (int64_t)(now - pl->last_guest_time) > 0 )
+ pl->last_guest_time = now;
+ else
+ now = ++pl->last_guest_time;
+ }
spin_unlock(&pl->pl_time_lock);
return now + v->arch.hvm_vcpu.stime_offset;
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 000191b..d424c70 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -712,13 +712,16 @@ static unsigned long get_cmos_time(void)
* System Time
***************************************************************************/
-s_time_t get_s_time(void)
+s_time_t get_s_time_fixed(u64 at_tsc)
{
struct cpu_time *t = &this_cpu(cpu_time);
u64 tsc, delta;
s_time_t now;
- rdtscll(tsc);
+ if ( at_tsc )
+ tsc = at_tsc;
+ else
+ rdtscll(tsc);
delta = tsc - t->local_tsc_stamp;
now = t->stime_local_stamp + scale_delta(delta, &t->tsc_scale);
diff --git a/xen/common/hvm/save.c b/xen/common/hvm/save.c
index 6c16399..7db68af 100644
--- a/xen/common/hvm/save.c
+++ b/xen/common/hvm/save.c
@@ -186,6 +186,8 @@ int hvm_save(struct domain *d, hvm_domain_context_t *h)
}
}
+ arch_hvm_save_done(d);
+
/* Save an end-of-file marker */
if ( hvm_save_entry(END, 0, h, &end) != 0 )
{
@@ -236,7 +238,10 @@ int hvm_load(struct domain *d, hvm_domain_context_t *h)
/* Read the typecode of the next entry and check for the end-marker */
desc = (struct hvm_save_descriptor *)(&h->data[h->cur]);
if ( desc->typecode == 0 )
+ {
+ arch_hvm_load_done(d);
return 0;
+ }
/* Find the handler for this entry */
if ( (desc->typecode > HVM_SAVE_CODE_MAX) ||
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index 49f7c0c..201f856 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -308,6 +308,8 @@ struct arch_domain
(possibly other cases in the future */
uint64_t vtsc_kerncount; /* for hvm, counts all vtsc */
uint64_t vtsc_usercount; /* not used for hvm */
+ uint64_t chkpt_tsc; /* TSC value that VCPUs use to calculate their
+ tsc_offset value. Used during save/restore */
/* Pseudophysical e820 map (XENMEM_memory_map). */
spinlock_t e820_lock;
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index dcc3483..d80e763 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -232,12 +232,15 @@ bool_t hvm_send_assist_req(struct vcpu *v);
void hvm_get_guest_pat(struct vcpu *v, u64 *guest_pat);
int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat);
-void hvm_set_guest_tsc(struct vcpu *v, u64 guest_tsc);
-u64 hvm_get_guest_tsc(struct vcpu *v);
+void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc);
+#define hvm_set_guest_tsc(v, t) hvm_set_guest_tsc_fixed((v), (t), 0)
+u64 hvm_get_guest_tsc_fixed(struct vcpu *v, u64 at_tsc);
+#define hvm_get_guest_tsc(v) hvm_get_guest_tsc_fixed((v), 0)
void hvm_init_guest_time(struct domain *d);
void hvm_set_guest_time(struct vcpu *v, u64 guest_time);
-u64 hvm_get_guest_time(struct vcpu *v);
+u64 hvm_get_guest_time_fixed(struct vcpu *v, u64 at_tsc);
+#define hvm_get_guest_time(v) hvm_get_guest_time_fixed((v), 0)
int vmsi_deliver(
struct domain *d, int vector,
diff --git a/xen/include/xen/hvm/save.h b/xen/include/xen/hvm/save.h
index ae6f0bb..70522a9 100644
--- a/xen/include/xen/hvm/save.h
+++ b/xen/include/xen/hvm/save.h
@@ -133,6 +133,8 @@ int hvm_load(struct domain *d, hvm_domain_context_t *h);
/* Arch-specific definitions. */
struct hvm_save_header;
void arch_hvm_save(struct domain *d, struct hvm_save_header *hdr);
+void arch_hvm_save_done(struct domain *d);
int arch_hvm_load(struct domain *d, struct hvm_save_header *hdr);
+void arch_hvm_load_done(struct domain *d);
#endif /* __XEN_HVM_SAVE_H__ */
diff --git a/xen/include/xen/time.h b/xen/include/xen/time.h
index 95b4b91..032eb23 100644
--- a/xen/include/xen/time.h
+++ b/xen/include/xen/time.h
@@ -32,7 +32,8 @@ struct vcpu;
typedef s64 s_time_t;
#define PRI_stime PRId64
-s_time_t get_s_time(void);
+s_time_t get_s_time_fixed(u64 at_tick);
+#define get_s_time() get_s_time_fixed(0)
unsigned long get_localtime(struct domain *d);
uint64_t get_localtime_us(struct domain *d);
--
1.7.10.4
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