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

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Message-ID: <58b4b445-bd47-d357-9fdd-118043624215@redhat.com>
Date:   Thu, 21 Nov 2019 17:02:42 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     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 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.

Thanks,

Paolo