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SubjectRe: [PATCH 7/8] x86/svm: Set IBPB when running a different VCPU
On Tue, Jan 09, 2018 at 01:03:09PM +0100, Paolo Bonzini wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> Set IBPB (Indirect Branch Prediction Barrier) when the current CPU is
> going to run a VCPU different from what was previously run. Nested
> virtualization uses the same VMCB for the second level guest, but the
> L1 hypervisor should be using IBRS to protect itself.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/svm.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 934a21e02e03..97126c2bd663 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -289,6 +289,7 @@ struct amd_svm_iommu_ir {
> module_param(vgif, int, 0444);
>
> static bool __read_mostly have_spec_ctrl;
> +static bool __read_mostly have_ibpb_support;
>
> static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
> static void svm_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa);
> @@ -540,6 +541,7 @@ struct svm_cpu_data {
> struct kvm_ldttss_desc *tss_desc;
>
> struct page *save_area;
> + struct vmcb *current_vmcb;
> };
>
> static DEFINE_PER_CPU(struct svm_cpu_data *, svm_data);
> @@ -1151,6 +1153,11 @@ static __init int svm_hardware_setup(void)
> pr_info("kvm: SPEC_CTRL available\n");
> else
> pr_info("kvm: SPEC_CTRL not available\n");
> + have_ibpb_support = have_spec_ctrl || cpu_has_ibpb_support();
> + if (have_ibpb_support)
> + pr_info("kvm: IBPB_SUPPORT available\n");
> + else
> + pr_info("kvm: IBPB_SUPPORT not available\n");

pr_info("kvm: IBPB_SUPPORT %s available" .. you know :-)

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