Re: [BISECTED] KVM error with 5.0-rc

[Sean Christopherson <sean.j.christopherson@intel.com>]

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On Mon, Jan 14, 2019 at 06:04:27PM +0100, Harald Arnesen wrote:
> Qemu with KVM acceleration fails with kernel 5.0-rc1 and 5.0-rc2.
> It works fine with 4.20.

...

> Bisecting gives:
> 
> c73da3fcab43357feb68cac227194b13e998a8db is the first bad commit
> commit c73da3fcab43357feb68cac227194b13e998a8db
> Author: Sean Christopherson <sean.j.christopherson@intel.com>
> Date:   Mon Dec 3 13:53:00 2018 -0800
> 
>     KVM: VMX: Properly handle dynamic VM Entry/Exit controls
> 
>     EFER and PERF_GLOBAL_CTRL MSRs have dedicated VM Entry/Exit controls
>     that KVM dynamically toggles based on whether or not the guest's value
>     for each MSRs differs from the host.  Handle the dynamic behavior by
>     adding a helper that clears the dynamic bits so the bits aren't set
>     when initializing the VMCS field outside of the dynamic toggling flow.
>     This makes the handling consistent with similar behavior for other
>     controls, e.g. pin, exec and sec_exec.  More importantly, it eliminates
>     two global bools that are stealthily modified by setup_vmcs_config.
> 
>     Opportunistically clean up a comment and print related to errata for
>     IA32_PERF_GLOBAL_CTRL.
> 
>     Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
>     Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Can you test the attached patch?  Found a bug when re-inspecting the
guilty commit, the wrong VMCS field is being modifying when applying an
errata to disable VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL.  Your CPU is
listed as one of the models affected by the errata.  Compile tested only.

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From 6dde876a992ca2e3627b1fe7aca3975487bc1da6 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Mon, 14 Jan 2019 10:23:46 -0800
Subject: [PATCH] KVM: VMX: Use the correct var field when clearing
 VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL

Fix a recently introduced bug that results in the wrong VMCS control
field being updated when applying a IA32_PERF_GLOBAL_CTRL errata.

Fixes: c73da3fcab43 ("KVM: VMX: Properly handle dynamic VM Entry/Exit controls")
Reported-by: Harald Arnesen <harald@skogtun.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/vmx/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f6915f10e584..0762fcab8fc9 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2344,7 +2344,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 		case 37: /* AAT100 */
 		case 44: /* BC86,AAY89,BD102 */
 		case 46: /* BA97 */
-			_vmexit_control &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
+			_vmentry_control &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
 			_vmexit_control &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
 			pr_warn_once("kvm: VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL "
 					"does not work properly. Using workaround\n");
-- 
2.19.2