The patch below does not apply to the 4.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2cf7ea9f40fabee0f8b40db4eb2d1e85cc6c0a95 Mon Sep 17 00:00:00 2001

From: Paolo Bonzini pbonzini@redhat.com Date: Wed, 3 Oct 2018 10:34:00 +0200 Subject: [PATCH] KVM: VMX: hide flexpriority from guest when disabled at the module level

As of commit 8d860bbeedef ("kvm: vmx: Basic APIC virtualization controls have three settings"), KVM will disable VIRTUALIZE_APIC_ACCESSES when a nested guest writes APIC_BASE MSR and kvm-intel.flexpriority=0, whereas previously KVM would allow a nested guest to enable VIRTUALIZE_APIC_ACCESSES so long as it's supported in hardware. That is, KVM now advertises VIRTUALIZE_APIC_ACCESSES to a guest but doesn't (always) allow setting it when kvm-intel.flexpriority=0, and may even initially allow the control and then clear it when the nested guest writes APIC_BASE MSR, which is decidedly odd even if it doesn't cause functional issues.

Hide the control completely when the module parameter is cleared.

reported-by: Sean Christopherson sean.j.christopherson@intel.com Fixes: 8d860bbeedef ("kvm: vmx: Basic APIC virtualization controls have three settings") Cc: Jim Mattson jmattson@google.com Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 764ae031054f..55b62760b694 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3589,12 +3589,12 @@ static void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, bool apicv) msrs->secondary_ctls_high); msrs->secondary_ctls_low = 0; msrs->secondary_ctls_high &= - SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES | SECONDARY_EXEC_DESC | SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE | SECONDARY_EXEC_APIC_REGISTER_VIRT | SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY | SECONDARY_EXEC_WBINVD_EXITING; + /* * We can emulate "VMCS shadowing," even if the hardware * doesn't support it. @@ -3651,6 +3651,10 @@ static void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, bool apicv) msrs->secondary_ctls_high |= SECONDARY_EXEC_UNRESTRICTED_GUEST;

+ if (flexpriority_enabled) + msrs->secondary_ctls_high |= + SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES; + /* miscellaneous data */ rdmsr(MSR_IA32_VMX_MISC, msrs->misc_low,