[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 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. (As part of the patch, update rdtscll's definition so that its variables don't clash with outer code) Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx> --- xen/arch/x86/hvm/hvm.c | 16 ++++++++++++---- xen/arch/x86/hvm/save.c | 16 ++++++++++++++++ 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 | 12 ++++++++++-- xen/common/hvm/save.c | 5 +++++ xen/include/asm-x86/domain.h | 2 ++ xen/include/asm-x86/hvm/hvm.h | 9 ++++++--- xen/include/asm-x86/msr.h | 6 +++--- xen/include/xen/hvm/save.h | 2 ++ xen/include/xen/time.h | 1 + 12 files changed, 71 insertions(+), 22 deletions(-) diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index ae24211..edf2824 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -248,16 +248,20 @@ 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 if ( at_tsc ) + { + tsc = at_tsc; + } else { rdtscll(tsc); @@ -279,16 +283,20 @@ 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 if ( at_tsc ) + { + tsc = at_tsc; + } else { rdtscll(tsc); diff --git a/xen/arch/x86/hvm/save.c b/xen/arch/x86/hvm/save.c index 066fdb2..309a1fd 100644 --- a/xen/arch/x86/hvm/save.c +++ b/xen/arch/x86/hvm/save.c @@ -34,6 +34,14 @@ void arch_hvm_save(struct domain *d, struct hvm_save_header *hdr) /* Save guest's preferred TSC. */ hdr->gtsc_khz = d->arch.tsc_khz; + + /* Time when saving started */ + rdtscll(d->arch.chkpt_tsc); +} + +void arch_hvm_save_done(struct domain *d) +{ + d->arch.chkpt_tsc = 0; } int arch_hvm_load(struct domain *d, struct hvm_save_header *hdr) @@ -67,12 +75,20 @@ int arch_hvm_load(struct domain *d, struct hvm_save_header *hdr) if ( d->arch.vtsc ) hvm_set_rdtsc_exiting(d, 1); + /* Time when restore started */ + rdtscll(d->arch.chkpt_tsc); + /* VGA state is not saved/restored, so we nobble the cache. */ d->arch.hvm_domain.stdvga.cache = 0; return 0; } +void arch_hvm_load_done(struct domain *d) +{ + d->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..b044717 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -712,19 +712,27 @@ 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); return now; } +s_time_t get_s_time() +{ + return get_s_time_fixed(0); +} + uint64_t tsc_ticks2ns(uint64_t ticks) { struct cpu_time *t = &this_cpu(cpu_time); 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..535b078 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/asm-x86/msr.h b/xen/include/asm-x86/msr.h index 61f579a..52cae4b 100644 --- a/xen/include/asm-x86/msr.h +++ b/xen/include/asm-x86/msr.h @@ -78,9 +78,9 @@ static inline int wrmsr_safe(unsigned int msr, uint64_t val) __asm__ __volatile__("rdtsc" : "=a" (low) : : "edx") #define rdtscll(val) do { \ - unsigned int a,d; \ - asm volatile("rdtsc" : "=a" (a), "=d" (d)); \ - (val) = ((unsigned long)a) | (((unsigned long)d)<<32); \ + unsigned int _eax, _edx; \ + asm volatile("rdtsc" : "=a" (_eax), "=d" (_edx)); \ + (val) = ((unsigned long)_eax) | (((unsigned long)_edx)<<32); \ } while(0) #define __write_tsc(val) wrmsrl(MSR_IA32_TSC, val) 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..d20d356 100644 --- a/xen/include/xen/time.h +++ b/xen/include/xen/time.h @@ -32,6 +32,7 @@ struct vcpu; typedef s64 s_time_t; #define PRI_stime PRId64 +s_time_t get_s_time_fixed(u64 at_tick); s_time_t get_s_time(void); unsigned long get_localtime(struct domain *d); uint64_t get_localtime_us(struct domain *d); -- 1.7.10.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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