Re: [PATCH v3 2/4] KVM/X86: Intel MPX vmx and msr handle

From: Paolo Bonzini
Date: Wed Jan 22 2014 - 06:49:09 EST

Il 22/01/2014 12:38, Paolo Bonzini ha scritto:
Il 21/01/2014 20:01, Liu, Jinsong ha scritto:
From 31e68d752ac395dc6b65e6adf45be5324e92cdc8 Mon Sep 17 00:00:00 2001
From: Liu Jinsong <jinsong.liu@xxxxxxxxx>
Date: Fri, 13 Dec 2013 02:32:43 +0800
Subject: [PATCH v3 2/4] KVM/X86: Intel MPX vmx and msr handle

This patch handle vmx and msr of Intel MPX feature.

Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>
Signed-off-by: Liu Jinsong <jinsong.liu@xxxxxxxxx>
---
arch/x86/include/asm/vmx.h | 2 ++
arch/x86/include/uapi/asm/msr-index.h | 1 +
arch/x86/kvm/vmx.c | 12 ++++++++++--
3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 966502d..1bf4681 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -85,6 +85,7 @@
#define VM_EXIT_SAVE_IA32_EFER 0x00100000
#define VM_EXIT_LOAD_IA32_EFER 0x00200000
#define VM_EXIT_SAVE_VMX_PREEMPTION_TIMER 0x00400000
+#define VM_EXIT_CLEAR_BNDCFGS 0x00800000

#define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR 0x00036dff

@@ -95,6 +96,7 @@
#define VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL 0x00002000
#define VM_ENTRY_LOAD_IA32_PAT 0x00004000
#define VM_ENTRY_LOAD_IA32_EFER 0x00008000
+#define VM_ENTRY_LOAD_BNDCFGS 0x00010000

#define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR 0x000011ff

diff --git a/arch/x86/include/uapi/asm/msr-index.h
b/arch/x86/include/uapi/asm/msr-index.h
index 37813b5..2a418c4 100644
--- a/arch/x86/include/uapi/asm/msr-index.h
+++ b/arch/x86/include/uapi/asm/msr-index.h
@@ -294,6 +294,7 @@
#define MSR_SMI_COUNT 0x00000034
#define MSR_IA32_FEATURE_CONTROL 0x0000003a
#define MSR_IA32_TSC_ADJUST 0x0000003b
+#define MSR_IA32_BNDCFGS 0x00000d90

#define FEATURE_CONTROL_LOCKED (1<<0)
#define FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX (1<<1)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b2fe1c2..6d7d9ad 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -439,6 +439,7 @@ struct vcpu_vmx {
#endif
int gs_ldt_reload_needed;
int fs_reload_needed;
+ u64 msr_host_bndcfgs;
} host_state;
struct {
int vm86_active;
@@ -1647,6 +1648,8 @@ static void vmx_save_host_state(struct kvm_vcpu
*vcpu)
if (is_long_mode(&vmx->vcpu))
wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
#endif
+ if (boot_cpu_has(X86_FEATURE_MPX))
+ rdmsrl(MSR_IA32_BNDCFGS, vmx->host_state.msr_host_bndcfgs);
for (i = 0; i < vmx->save_nmsrs; ++i)
kvm_set_shared_msr(vmx->guest_msrs[i].index,
vmx->guest_msrs[i].data,
@@ -1684,6 +1687,8 @@ static void __vmx_load_host_state(struct
vcpu_vmx *vmx)
#ifdef CONFIG_X86_64
wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
#endif
+ if (vmx->host_state.msr_host_bndcfgs)
+ wrmsrl(MSR_IA32_BNDCFGS, vmx->host_state.msr_host_bndcfgs);
/*
* If the FPU is not active (through the host task or
* the guest vcpu), then restore the cr0.TS bit.
@@ -2800,7 +2805,7 @@ static __init int setup_vmcs_config(struct
vmcs_config *vmcs_conf)
min |= VM_EXIT_HOST_ADDR_SPACE_SIZE;
#endif
opt = VM_EXIT_SAVE_IA32_PAT | VM_EXIT_LOAD_IA32_PAT |
- VM_EXIT_ACK_INTR_ON_EXIT;
+ VM_EXIT_ACK_INTR_ON_EXIT | VM_EXIT_CLEAR_BNDCFGS;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_EXIT_CTLS,
&_vmexit_control) < 0)
return -EIO;
@@ -2817,7 +2822,7 @@ static __init int setup_vmcs_config(struct
vmcs_config *vmcs_conf)
_pin_based_exec_control &= ~PIN_BASED_POSTED_INTR;

min = 0;
- opt = VM_ENTRY_LOAD_IA32_PAT;
+ opt = VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_LOAD_BNDCFGS;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_ENTRY_CTLS,
&_vmentry_control) < 0)
return -EIO;

You need to disable MPX in the guest if the two controls are not
available. You can do this, for example, in vmx_cpuid_update.

Better: add a mpx_supported field to struct kvm_x86_ops. You can use invpcid_supported as a model.

Otherwise, nested VMX is broken.

@@ -8636,6 +8641,9 @@ static int __init vmx_init(void)
vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_CS, false);
vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_ESP, false);
vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
+ if (boot_cpu_has(X86_FEATURE_MPX))
+ vmx_disable_intercept_for_msr(MSR_IA32_BNDCFGS, true);

This needs to be done unconditionally. Otherwise, reading/writing
BNDCFGS will access a nonexistent VMCS field.

Paolo

memcpy(vmx_msr_bitmap_legacy_x2apic,
vmx_msr_bitmap_legacy, PAGE_SIZE);
memcpy(vmx_msr_bitmap_longmode_x2apic,



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