linux-kernel - Re: [PATCHv5 11/19] x86/mm: Implement vma

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Date:   Wed, 18 Jul 2018 16:40:14 -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: [PATCHv5 11/19] x86/mm: Implement vma_keyid()

> --- a/arch/x86/mm/mktme.c
> +++ b/arch/x86/mm/mktme.c
> @@ -1,3 +1,4 @@
> +#include <linux/mm.h>
>  #include <asm/mktme.h>
>  
>  phys_addr_t mktme_keyid_mask;
> @@ -37,3 +38,14 @@ struct page_ext_operations page_mktme_ops = {
>  	.need = need_page_mktme,
>  	.init = init_page_mktme,
>  };
> +
> +int vma_keyid(struct vm_area_struct *vma)
> +{
> +	pgprotval_t prot;
> +
> +	if (!mktme_enabled())
> +		return 0;
> +
> +	prot = pgprot_val(vma->vm_page_prot);
> +	return (prot & mktme_keyid_mask) >> mktme_keyid_shift;
> +}

I'm a bit surprised this isn't inlined.  Not that function calls are
expensive, but we *could* entirely avoid them using the normal pattern of:

// In the header:
static inline vma_keyid(...)
{
	if (!mktme_enabled())
		return 0;

	return __vma_keyid(...); // <- the .c file version
}