linux-kernel - Re: [PATCH v7 2/9] vmx: spp: Add control flags for Sub-Page Protection(SPP)

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Date:   Fri, 22 Nov 2019 23:23:31 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, jmattson@...gle.com,
        sean.j.christopherson@...el.com, yu.c.zhang@...ux.intel.com,
        alazar@...defender.com, edwin.zhai@...el.com
Subject: Re: [PATCH v7 2/9] vmx: spp: Add control flags for Sub-Page
 Protection(SPP)

On Thu, Nov 21, 2019 at 05:02:42PM +0100, Paolo Bonzini wrote:
> On 21/11/19 16:34, Yang Weijiang wrote:
> > On Thu, Nov 21, 2019 at 11:04:51AM +0100, Paolo Bonzini wrote:
> >> On 19/11/19 09:49, Yang Weijiang wrote:
> >>> @@ -228,6 +228,7 @@
> >>>  #define X86_FEATURE_FLEXPRIORITY	( 8*32+ 2) /* Intel FlexPriority */
> >>>  #define X86_FEATURE_EPT			( 8*32+ 3) /* Intel Extended Page Table */
> >>>  #define X86_FEATURE_VPID		( 8*32+ 4) /* Intel Virtual Processor ID */
> >>> +#define X86_FEATURE_SPP			( 8*32+ 5) /* Intel EPT-based Sub-Page Write Protection */
> >>
> >> Please do not include X86_FEATURE_SPP.  In general I don't like the VMX
> >> features word, but apart from that SPP is not a feature that affects all
> >> VMs in the same way as EPT or FlexPriority.
> >>
> > So what's a friendly way to let a user check if SPP feature is there?
> 
> QEMU for example ships with a program called vmxcap (though it requires
> root).  We also could write a program to analyze the KVM capabilities
> and print them, and put it in tools/kvm.
>
OK, will update vmxcap to add SPP feature bit, thanks!
> Thanks,
> 
> Paolo