On 8/15/19 3:44 PM, Jim Mattson wrote:
On Wed, Apr 24, 2019 at 4:43 PM Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx> wrote:According to section "Loading Guest State" in Intel SDM vol 3C, the IA32_PERF_GLOBAL_CTRL MSR is loaded on vmentry of nested guests: "If the “load IA32_PERF_GLOBAL_CTRL” VM-entry control is 1, the IA32_PERF_GLOBAL_CTRL MSR is loaded from the IA32_PERF_GLOBAL_CTRL field." Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx> Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx> Reviewed-by: Karl Heubaum <karl.heubaum@xxxxxxxxxx> --- arch/x86/kvm/vmx/nested.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index a7bf19eaa70b..8177374886a9 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2300,6 +2300,10 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, vcpu->arch.cr0_guest_owned_bits &= ~vmcs12->cr0_guest_host_mask; vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits); + if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL) + vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL, + vmcs12->guest_ia32_perf_global_ctrl); + if (vmx->nested.nested_run_pending && (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PAT)) { vmcs_write64(GUEST_IA32_PAT, vmcs12->guest_ia32_pat); -- 2.17.2This isn't quite right. The GUEST_IA32_PERF_GLOBAL_CTRL value is just going to get overwritten later by atomic_switch_perf_msrs().
atomic_switch_perf_msrs() gest called from vmx_vcpu_run() which I thought was executing before handle_vmlaunch() stuff that lead to prepare_vmcs02(). Did I miss something in the call-chain ?
Instead of writing the vmcs12 value directly into the vmcs02, you should call kvm_set_msr(), exactly as it would have been called if MSR_CORE_PERF_GLOBAL_CTRL had been in the vmcs12 VM-entry MSR-load list. Then, atomic_switch_perf_msrs() will automatically do the right thing.
