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[Xen-changelog] [xen master] x86/HVM: use fixed TSC value when saving or restoring domain

Date: Wed, 23 Apr 2014 11:11:44 +0000

Delivery-date: Wed, 23 Apr 2014 11:11:59 +0000

List-id: "Change log for Mercurial \(receive only\)" <xen-changelog.lists.xen.org>

commit 88e64cb785c1de4f686c1aa1993a0003b7db9e1a Author: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> AuthorDate: Tue Apr 22 12:08:56 2014 +0200 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Tue Apr 22 12:08:56 2014 +0200 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. Reported-by: Philippe Coquard <philippe.coquard@xxxxxxxx> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- xen/arch/x86/hvm/hvm.c | 10 +++++++--- xen/arch/x86/hvm/save.c | 6 ++++++ xen/arch/x86/hvm/svm/svm.c | 5 +++-- xen/arch/x86/hvm/vmx/vmx.c | 5 +++-- xen/include/asm-x86/hvm/hvm.h | 3 ++- 5 files changed, 21 insertions(+), 8 deletions(-) diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index 15f4b25..44fbb69 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -258,16 +258,20 @@ 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); @@ -278,7 +282,7 @@ void hvm_set_guest_tsc(struct vcpu *v, u64 guest_tsc) - v->arch.hvm_vcpu.cache_tsc_offset; v->arch.hvm_vcpu.cache_tsc_offset = delta_tsc; - hvm_funcs.set_tsc_offset(v, v->arch.hvm_vcpu.cache_tsc_offset, 0); + hvm_funcs.set_tsc_offset(v, v->arch.hvm_vcpu.cache_tsc_offset, at_tsc); } void hvm_set_guest_tsc_adjust(struct vcpu *v, u64 tsc_adjust) diff --git a/xen/arch/x86/hvm/save.c b/xen/arch/x86/hvm/save.c index 066fdb2..6af19be 100644 --- a/xen/arch/x86/hvm/save.c +++ b/xen/arch/x86/hvm/save.c @@ -34,6 +34,9 @@ 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.hvm_domain.sync_tsc); } int arch_hvm_load(struct domain *d, struct hvm_save_header *hdr) @@ -67,6 +70,9 @@ 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.hvm_domain.sync_tsc); + /* VGA state is not saved/restored, so we nobble the cache. */ d->arch.hvm_domain.stdvga.cache = 0; diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c index 4cc271e..3fe4b9c 100644 --- a/xen/arch/x86/hvm/svm/svm.c +++ b/xen/arch/x86/hvm/svm/svm.c @@ -318,7 +318,8 @@ 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.hvm_domain.sync_tsc); } @@ -334,7 +335,7 @@ 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.hvm_domain.sync_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 1c9fa48..104e6e4 100644 --- a/xen/arch/x86/hvm/vmx/vmx.c +++ b/xen/arch/x86/hvm/vmx/vmx.c @@ -540,7 +540,8 @@ 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.hvm_domain.sync_tsc); } static void vmx_load_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data) @@ -556,7 +557,7 @@ 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.hvm_domain.sync_tsc); } diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h index 1fb3b99..31043b2 100644 --- a/xen/include/asm-x86/hvm/hvm.h +++ b/xen/include/asm-x86/hvm/hvm.h @@ -232,7 +232,8 @@ 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); +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) -- generated by git-patchbot for /home/xen/git/xen.git#master _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxx http://lists.xensource.com/xen-changelog

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