From 150360a6678afafbb1c25ec947bed2e4002baf87 Mon Sep 17 00:00:00 2001
From: Zelin Deng <zelin.deng@linux.alibaba.com>
Date: Wed, 28 Apr 2021 10:22:01 +0800
Subject: [PATCH] KVM: x86: Update vCPU's hv_clock before back to guest when tsc_offset is adjusted
Git-commit: d9130a2dfdd4b21736c91b818f87dbc0ccd1e757
Patch-mainline: v5.15-rc1
References: stable-5.14.4
commit d9130a2dfdd4b21736c91b818f87dbc0ccd1e757 upstream.
When MSR_IA32_TSC_ADJUST is written by guest due to TSC ADJUST feature
especially there's a big tsc warp (like a new vCPU is hot-added into VM
which has been up for a long time), tsc_offset is added by a large value
then go back to guest. This causes system time jump as tsc_timestamp is
not adjusted in the meantime and pvclock monotonic character.
To fix this, just notify kvm to update vCPU's guest time before back to
guest.
Cc: stable@vger.kernel.org
Signed-off-by: Zelin Deng <zelin.deng@linux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: <1619576521-81399-2-git-send-email-zelin.deng@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
arch/x86/kvm/x86.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e5d5c5ed7dd4..7ec7c2dce506 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3316,6 +3316,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (!msr_info->host_initiated) {
s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr;
adjust_tsc_offset_guest(vcpu, adj);
+ /* Before back to guest, tsc_timestamp must be adjusted
+ * as well, otherwise guest's percpu pvclock time could jump.
+ */
+ kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
}
vcpu->arch.ia32_tsc_adjust_msr = data;
}
--
2.26.2