Re: [PATCH 1/2] KVM: MMU: fix SMAP virtualization

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Xiao Guangrong <guangrong.xiao@linux.intel.com>, pbonzini@redhat.com
Cc: gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] KVM: MMU: fix SMAP virtualization
Date: Fri, 22 May 2015 16:43:18 -0400	[thread overview]
Message-ID: <555F94E6.3010200@oracle.com> (raw)
In-Reply-To: <1431356122-8500-1-git-send-email-guangrong.xiao@linux.intel.com>

On 05/11/2015 10:55 AM, Xiao Guangrong wrote:
> KVM may turn a user page to a kernel page when kernel writes a readonly
> user page if CR0.WP = 1. This shadow page entry will be reused after
> SMAP is enabled so that kernel is allowed to access this user page
>
> Fix it by setting SMAP && !CR0.WP into shadow page's role and reset mmu
> once CR4.SMAP is updated
>
> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> ---

>
> @@ -4208,12 +4211,18 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>   		       const u8 *new, int bytes)
>   {
>   	gfn_t gfn = gpa >> PAGE_SHIFT;
> -	union kvm_mmu_page_role mask = { .word = 0 };
>   	struct kvm_mmu_page *sp;
>   	LIST_HEAD(invalid_list);
>   	u64 entry, gentry, *spte;
>   	int npte;
>   	bool remote_flush, local_flush, zap_page;
> +	union kvm_mmu_page_role mask = (union kvm_mmu_page_role) {
> +		.cr0_wp = 1,
> +		.cr4_pae = 1,
> +		.nxe = 1,
> +		.smep_andnot_wp = 1,
> +		.smap_andnot_wp = 1,
> +	};
>
>

This breaks older compilers that can't initialize anon structures.

-boris