linux-kernel - Re: [PATCH v2] KVM/nVMX: Do not validate that posted_intr_desc

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Message-ID: <57f63d5b-903c-4b28-da79-151528dc7316@oracle.com>
Date:   Mon, 22 Oct 2018 16:23:03 -0700
From:   Krish Sadhukhan <krish.sadhukhan@...cle.com>
To:     KarimAllah Ahmed <karahmed@...zon.de>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH v2] KVM/nVMX: Do not validate that posted_intr_desc_addr
 is page aligned



On 10/20/2018 03:50 PM, KarimAllah Ahmed wrote:
> The spec only requires the posted interrupt descriptor address to be
> 64-bytes aligned (i.e. bits[0:5] == 0). Using page_address_valid also
> forces the address to be page aligned.
>
> Only validate that the address does not cross the maximum physical address
> without enforcing a page alignment.
>
> v1 -> v2:
> - Add a missing parenthesis (dropped while merging!)
>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Fixes: 6de84e581c0 ("nVMX x86: check posted-interrupt descriptor addresss on vmentry of L2")
> Signed-off-by: KarimAllah Ahmed <karahmed@...zon.de>
> ---
>   arch/x86/kvm/vmx.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 38f1a16..bb0fcdb 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11667,7 +11667,7 @@ static int nested_vmx_check_apicv_controls(struct kvm_vcpu *vcpu,
>   	    !nested_exit_intr_ack_set(vcpu) ||
>   	    (vmcs12->posted_intr_nv & 0xff00) ||
>   	    (vmcs12->posted_intr_desc_addr & 0x3f) ||
> -	    (!page_address_valid(vcpu, vmcs12->posted_intr_desc_addr))))
> +	    (vmcs12->posted_intr_desc_addr >> cpuid_maxphyaddr(vcpu))))
>   		return -EINVAL;
>   
>   	/* tpr shadow is needed by all apicv features. */

Reviewed-by: Krish Sadhuhan <krish.sadhukhan@...cle.com>