linux-kernel - Re: [PATCHv3 08/17] x86/mm: Implement vma_is_encrypted() and vma

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Date:   Wed, 13 Jun 2018 11:18:05 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv3 08/17] x86/mm: Implement vma_is_encrypted() and
 vma_keyid()

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?