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

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Date:	Tue, 28 Jun 2016 22:17:54 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Bandan Das <bsd@...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



On 28/06/2016 19:33, Bandan Das wrote:
>>> >>  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.

It's okay to it like this, because the only invalid PTEs reaching this
point are those that is_mmio_spte filters away.  Hence you'll never get
-W- PTEs here, and pte & 7 is really the same as how you wrote it.  It's
pretty clever, and doesn't need a TODO at all. :)

Paolo