linux-kernel - Re: [PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page

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Date:	Mon, 18 Aug 2014 13:18:37 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
CC:	Gleb Natapov <gleb@...nel.org>, hpa@...or.com, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page

Il 18/08/2014 12:52, Xiao Guangrong ha scritto:
>> > EPT misconfig handler in kvm will check which reason lead to EPT 
>> > misconfiguration after vmexit. One of the reasons is that an EPT 
>> > paging-structure entry is configured with settings reserved for 
>> > future functionality. However, the handler can't identify if 
>> > paging-structure entry of reserved bits for 1-GByte page are 
>> > configured, since PDPTE which point to 1-GByte page will reserve 
>> > bits 29:12 instead of bits 7:3 which are reserved for PDPTE that 
>> > references an EPT Page Directory. This patch fix it by reserve 
>> > bits 29:12 for 1-GByte page. 
> That mask is only set in the lowest pte for 4K page, i think it
> is not a problem, no?

It will cause KVM to WARN.  The EPT memory type will also be ignored for
gigabyte pages.

Paolo
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