linux-kernel - Re: [PATCH] KVM: VMX: fix read/write sizes of VMCS fields

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Date:	Fri, 4 Dec 2015 10:05:14 +0800
From:	Yang Zhang <yang.zhang.wz@...il.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: VMX: fix read/write sizes of VMCS fields

On 2015/12/3 23:11, Paolo Bonzini wrote:
> In theory this should have broken EPT on 32-bit kernels (due to
> reading the high part of natural-width field GUEST_CR3).  Not sure
> if no one noticed or the processor behaves differently from the
> documentation.

It seems we will check the success of vmcs_write but not vmcs_read. 
Shouldn't check the vmcs_read?

>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>   arch/x86/kvm/vmx.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index c39737ff0581..b1af1e48070b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4868,7 +4868,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>
>   	seg_setup(VCPU_SREG_CS);
>   	vmcs_write16(GUEST_CS_SELECTOR, 0xf000);
> -	vmcs_write32(GUEST_CS_BASE, 0xffff0000);
> +	vmcs_writel(GUEST_CS_BASE, 0xffff0000ul);
>
>   	seg_setup(VCPU_SREG_DS);
>   	seg_setup(VCPU_SREG_ES);
> @@ -4904,7 +4904,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>
>   	vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
>   	vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, 0);
> -	vmcs_write32(GUEST_PENDING_DBG_EXCEPTIONS, 0);
> +	vmcs_writel(GUEST_PENDING_DBG_EXCEPTIONS, 0);
>
>   	setup_msrs(vmx);
>
> @@ -7893,7 +7893,7 @@ static void dump_vmcs(void)
>   	u32 pin_based_exec_ctrl = vmcs_read32(PIN_BASED_VM_EXEC_CONTROL);
>   	u32 secondary_exec_control = 0;
>   	unsigned long cr4 = vmcs_readl(GUEST_CR4);
> -	u64 efer = vmcs_readl(GUEST_IA32_EFER);
> +	u64 efer = vmcs_read64(GUEST_IA32_EFER);
>   	int i, n;
>
>   	if (cpu_has_secondary_exec_ctrls())
> @@ -10159,7 +10159,7 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>   	 * Additionally, restore L2's PDPTR to vmcs12.
>   	 */
>   	if (enable_ept) {
> -		vmcs12->guest_cr3 = vmcs_read64(GUEST_CR3);
> +		vmcs12->guest_cr3 = vmcs_readl(GUEST_CR3);
>   		vmcs12->guest_pdptr0 = vmcs_read64(GUEST_PDPTR0);
>   		vmcs12->guest_pdptr1 = vmcs_read64(GUEST_PDPTR1);
>   		vmcs12->guest_pdptr2 = vmcs_read64(GUEST_PDPTR2);
>



-- 
best regards
yang
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