lkml.org 
[lkml]   [2018]   [Apr]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 1/2] X86/KVM: Properly restore 'tsc_offset' when running an L2 guest
    Date
    When the TSC MSR is captured while an L2 guest is running then restored,
    the 'tsc_offset' ends up capturing the L02 TSC_OFFSET instead of the L01
    TSC_OFFSET. So ensure that this is compensated for when storing the value.

    Cc: Jim Mattson <jmattson@google.com>
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Radim Krčmář <rkrcmar@redhat.com>
    Cc: kvm@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
    ---
    arch/x86/kvm/vmx.c | 12 +++++++++---
    arch/x86/kvm/x86.c | 1 -
    2 files changed, 9 insertions(+), 4 deletions(-)

    diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    index cff2f50..2f57571 100644
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -2900,6 +2900,8 @@ static u64 guest_read_tsc(struct kvm_vcpu *vcpu)
    */
    static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
    {
    + u64 l1_tsc_offset = 0;
    +
    if (is_guest_mode(vcpu)) {
    /*
    * We're here if L1 chose not to trap WRMSR to TSC. According
    @@ -2908,16 +2910,20 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
    * to the newly set TSC to get L2's TSC.
    */
    struct vmcs12 *vmcs12;
    +
    /* recalculate vmcs02.TSC_OFFSET: */
    vmcs12 = get_vmcs12(vcpu);
    - vmcs_write64(TSC_OFFSET, offset +
    - (nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETING) ?
    - vmcs12->tsc_offset : 0));
    +
    + l1_tsc_offset = nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETING) ?
    + vmcs12->tsc_offset : 0;
    + vmcs_write64(TSC_OFFSET, offset + l1_tsc_offset);
    } else {
    trace_kvm_write_tsc_offset(vcpu->vcpu_id,
    vmcs_read64(TSC_OFFSET), offset);
    vmcs_write64(TSC_OFFSET, offset);
    }
    +
    + vcpu->arch.tsc_offset = offset - l1_tsc_offset;
    }

    /*
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index ac42c85..1a2ed92 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -1539,7 +1539,6 @@ EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
    static void kvm_vcpu_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
    {
    kvm_x86_ops->write_tsc_offset(vcpu, offset);
    - vcpu->arch.tsc_offset = offset;
    }

    static inline bool kvm_check_tsc_unstable(void)
    --
    2.7.4
    \
     
     \ /
      Last update: 2018-04-12 17:13    [W:2.293 / U:0.428 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site