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Subject: Re: [PATCHv3 08/17] x86/mm: Implement vma_is_encrypted() and
 vma_keyid()
References: <20180612143915.68065-1-kirill.shutemov@linux.intel.com>
 <20180612143915.68065-9-kirill.shutemov@linux.intel.com>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <cc63f92a-4020-79b5-9b49-4cdd5cb800d2@intel.com>
Date: Wed, 13 Jun 2018 11:18:05 -0700
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Sender: owner-linux-mm@kvack.org
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Ingo Molnar <mingo@redhat.com>, x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>, Tom Lendacky <thomas.lendacky@amd.com>
Cc: Kai Huang <kai.huang@linux.intel.com>, Jacob Pan <jacob.jun.pan@linux.intel.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org

On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote:
> +bool vma_is_encrypted(struct vm_area_struct *vma)
> +{
> +	return pgprot_val(vma->vm_page_prot) & mktme_keyid_mask;
> +}
> +
> +int vma_keyid(struct vm_area_struct *vma)
> +{
> +	pgprotval_t prot;
> +
> +	if (!vma_is_anonymous(vma))
> +		return 0;
> +
> +	prot = pgprot_val(vma->vm_page_prot);
> +	return (prot & mktme_keyid_mask) >> mktme_keyid_shift;
> +}

Why do we have a vma_is_anonymous() in one of these but not the other?

While this reuse of ->vm_page_prot is cute, is there any downside?  It's
the first place I know of that we can't derive ->vm_page_prot from
->vm_flags on non-VM_IO/PFNMAP VMAs.  Is that a problem?