linux-kernel - Re: [PATCH v5 01/13] X86/nVMX: handle_vmon: Read 4 bytes from guest memory

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Date:   Wed, 23 Jan 2019 11:59:45 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     KarimAllah Ahmed <karahmed@...zon.de>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pbonzini@...hat.com, rkrcmar@...hat.com
Subject: Re: [PATCH v5 01/13] X86/nVMX: handle_vmon: Read 4 bytes from guest
 memory

On Wed, Jan 09, 2019 at 10:42:01AM +0100, KarimAllah Ahmed wrote:
> Read the data directly from guest memory instead of the map->read->unmap
> sequence. This also avoids using kvm_vcpu_gpa_to_page() and kmap() which
> assumes that there is a "struct page" for guest memory.
> 
> Suggested-by: Jim Mattson <jmattson@...gle.com>
> Signed-off-by: KarimAllah Ahmed <karahmed@...zon.de>
> Reviewed-by: Jim Mattson <jmattson@...gle.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>

Mind if I join party?

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

> 
> ---
> v1 -> v2:
> - Massage commit message a bit.
> ---
>  arch/x86/kvm/vmx/nested.c | 14 +++-----------
>  1 file changed, 3 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 3170e29..536468a 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -4192,7 +4192,7 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
>  {
>  	int ret;
>  	gpa_t vmptr;
> -	struct page *page;
> +	uint32_t revision;
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  	const u64 VMXON_NEEDED_FEATURES = FEATURE_CONTROL_LOCKED
>  		| FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
> @@ -4241,18 +4241,10 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
>  	if (!PAGE_ALIGNED(vmptr) || (vmptr >> cpuid_maxphyaddr(vcpu)))
>  		return nested_vmx_failInvalid(vcpu);
>  
> -	page = kvm_vcpu_gpa_to_page(vcpu, vmptr);
> -	if (is_error_page(page))
> +	if (kvm_read_guest(vcpu->kvm, vmptr, &revision, sizeof(revision)) ||
> +	    revision != VMCS12_REVISION)
>  		return nested_vmx_failInvalid(vcpu);
>  
> -	if (*(u32 *)kmap(page) != VMCS12_REVISION) {
> -		kunmap(page);
> -		kvm_release_page_clean(page);
> -		return nested_vmx_failInvalid(vcpu);
> -	}
> -	kunmap(page);
> -	kvm_release_page_clean(page);
> -
>  	vmx->nested.vmxon_ptr = vmptr;
>  	ret = enter_vmx_operation(vcpu);
>  	if (ret)
> -- 
> 2.7.4
>