[Xen-changelog] [xen stable-4.11] x86/tsc: update vcpu time info on guest TSC adjustments

[patchbot@xxxxxxx]

commit 41d85cbeaff2bcb6ba1a28fcc322f91c4930b98b
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Nov 25 16:16:18 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Nov 25 16:16:18 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>
    master commit: 7eee9c16d6405a1a1f2e8c6472923db842c90cfb
    master date: 2019-10-23 17:01:56 +0100
---
 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 1924434960..2a9f40b6db 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -429,6 +429,8 @@ static void hvm_set_guest_tsc_msr(struct vcpu *v, u64 
guest_tsc)
     hvm_set_guest_tsc(v, guest_tsc);
     v->arch.hvm_vcpu.msr_tsc_adjust += v->arch.hvm_vcpu.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)
@@ -437,6 +439,8 @@ static void hvm_set_guest_tsc_adjust(struct vcpu *v, u64 
tsc_adjust)
                             - v->arch.hvm_vcpu.msr_tsc_adjust;
     hvm_funcs.set_tsc_offset(v, v->arch.hvm_vcpu.cache_tsc_offset, 0);
     v->arch.hvm_vcpu.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#stable-4.11

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