linux-kernel - Re: [PATCH 1/5] mmu: mark spte present if the x bit is set

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Message-ID: <jpgd1n1gqva.fsf@linux.bootlegged.copy>
Date:	Tue, 28 Jun 2016 13:33:45 -0400
From:	Bandan Das <bsd@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	kvm@...r.kernel.org, guangrong.xiao@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] mmu: mark spte present if the x bit is set

Paolo Bonzini <pbonzini@...hat.com> writes:

> On 28/06/2016 06:32, Bandan Das wrote:
>> This is safe because is_shadow_present_pte() is called
>> on host controlled page table and we know the spte is
>> valid
>> 
>> Signed-off-by: Bandan Das <bsd@...hat.com>
>> ---
>>  arch/x86/kvm/mmu.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index def97b3..a50af79 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -304,7 +304,8 @@ static int is_nx(struct kvm_vcpu *vcpu)
>>  
>>  static int is_shadow_present_pte(u64 pte)
>>  {
>> -	return pte & PT_PRESENT_MASK && !is_mmio_spte(pte);
>> +	return pte & (PT_PRESENT_MASK | shadow_x_mask) &&
>> +		!is_mmio_spte(pte);
>
> This should really be pte & 7 when using EPT.  But this is okay as an
> alternative to a new shadow_present_mask.

I could revive shadow_xonly_valid probably... Anyway, for now I will
add a TODO comment here.

> Paolo
>
>>  }
>>  
>>  static int is_large_pte(u64 pte)
>> 
> --
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