linux-kernel - Re: [PATCH 3/5] mmu: don't set the present bit unconditionally

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Message-ID: <5774C7C7.2080501@linux.intel.com>
Date:	Thu, 30 Jun 2016 15:18:31 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, Bandan Das <bsd@...hat.com>,
	kvm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] mmu: don't set the present bit unconditionally



On 06/29/2016 04:18 PM, Paolo Bonzini wrote:
>
>
> On 29/06/2016 05:17, Xiao Guangrong wrote:
>>>
>>> +++ b/arch/x86/kvm/mmu.c
>>> @@ -2516,13 +2516,17 @@ static int set_spte(struct kvm_vcpu *vcpu, u64
>>> *sptep,
>>>                gfn_t gfn, kvm_pfn_t pfn, bool speculative,
>>>                bool can_unsync, bool host_writable)
>>>    {
>>> -    u64 spte;
>>> +    u64 spte = 0;
>>>        int ret = 0;
>>> +    struct kvm_mmu *context = &vcpu->arch.mmu;
>>> +    bool execonly = !(context->guest_rsvd_check.bad_mt_xwr &
>>> +              (1ull << VMX_EPT_EXECUTABLE_MASK));
>>
>> Could we introduce a new field, say execonly, to "struct kvm_mmu"?
>> That would make the code be more clearer.
>
> Given how execonly is used, let's add shadow_present_mask instead.

Yup, it is better.