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

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Date:	Wed, 22 Jan 2014 12:38:07 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	"Liu, Jinsong" <jinsong.liu@...el.com>
CC:	"gleb@...hat.com" <gleb@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Ren, Qiaowei" <qiaowei.ren@...el.com>
Subject: Re: [PATCH v3 2/4] KVM/X86: Intel MPX vmx and msr handle

Il 21/01/2014 20:01, Liu, Jinsong ha scritto:
> From 31e68d752ac395dc6b65e6adf45be5324e92cdc8 Mon Sep 17 00:00:00 2001
> From: Liu Jinsong <jinsong.liu@...el.com>
> 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@...el.com>
> Signed-off-by: Liu Jinsong <jinsong.liu@...el.com>
> ---
>  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. 
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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