[Xen-changelog] [xen master] x86/tsc: update vcpu time info on guest TSC adjustments

[patchbot@xxxxxxx]

commit 7eee9c16d6405a1a1f2e8c6472923db842c90cfb
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Wed Oct 23 10:57:39 2019 +0200
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Oct 23 17:01:56 2019 +0100

    x86/tsc: update vcpu time info on guest TSC adjustments
    
    If a HVM/PVH guest writes to MSR_IA32_TSC{_ADJUST} and thus changes
    the value of the time stamp counter the vcpu time info must also be
    updated, or the time calculated by the guest using the Xen PV clock
    interface will be skewed.
    
    Update the vcpu time info when the guest writes to either MSR_IA32_TSC
    or MSR_IA32_TSC_ADJUST. This fixes lockups seen when running the
    pv-shim on AMD hardware, since the shim will aggressively try to keep
    TSCs in sync by periodically writing to MSR_IA32_TSC if the TSC is not
    reliable.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Wei Liu <wl@xxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 9acd359c99..e4c0425330 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -442,6 +442,8 @@ static void hvm_set_guest_tsc_msr(struct vcpu *v, u64 
guest_tsc)
 
     hvm_set_guest_tsc(v, guest_tsc);
     v->arch.hvm.msr_tsc_adjust += v->arch.hvm.cache_tsc_offset - tsc_offset;
+    if ( v == current )
+        update_vcpu_system_time(v);
 }
 
 static void hvm_set_guest_tsc_adjust(struct vcpu *v, u64 tsc_adjust)
@@ -449,6 +451,8 @@ static void hvm_set_guest_tsc_adjust(struct vcpu *v, u64 
tsc_adjust)
     v->arch.hvm.cache_tsc_offset += tsc_adjust - v->arch.hvm.msr_tsc_adjust;
     hvm_set_tsc_offset(v, v->arch.hvm.cache_tsc_offset, 0);
     v->arch.hvm.msr_tsc_adjust = tsc_adjust;
+    if ( v == current )
+        update_vcpu_system_time(v);
 }
 
 u64 hvm_get_guest_tsc_fixed(struct vcpu *v, uint64_t at_tsc)
--
generated by git-patchbot for /home/xen/git/xen.git#master

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