linux-kernel - Re: [PATCH v1 01/11] x86/mm/pat: factor out setting cachemode into pgprot_set

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Message-ID: <da28d743-8622-46fc-aa60-5db9c776bd87@lucifer.local>
Date: Mon, 28 Apr 2025 17:16:24 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-trace-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tursulin@...ulin.net>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Pedro Falcato <pfalcato@...e.de>, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH v1 01/11] x86/mm/pat: factor out setting cachemode into
 pgprot_set_cachemode()

On Fri, Apr 25, 2025 at 10:17:05AM +0200, David Hildenbrand wrote:
> Let's factor it out to make the code easier to grasp.
>
> Use it also in pgprot_writecombine()/pgprot_writethrough() where
> clearing the old cachemode might not be required, but given that we are
> already doing a function call, no need to care about this
> micro-optimization.

Ah my kind of patch :)

>
> Signed-off-by: David Hildenbrand <david@...hat.com>

LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  arch/x86/mm/pat/memtype.c | 33 +++++++++++++++------------------
>  1 file changed, 15 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
> index 72d8cbc611583..edec5859651d6 100644
> --- a/arch/x86/mm/pat/memtype.c
> +++ b/arch/x86/mm/pat/memtype.c
> @@ -800,6 +800,12 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
>  }
>  #endif /* CONFIG_STRICT_DEVMEM */
>
> +static inline void pgprot_set_cachemode(pgprot_t *prot, enum page_cache_mode pcm)
> +{
> +	*prot = __pgprot((pgprot_val(*prot) & ~_PAGE_CACHE_MASK) |
> +			 cachemode2protval(pcm));
> +}
> +
>  int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
>  				unsigned long size, pgprot_t *vma_prot)
>  {
> @@ -811,8 +817,7 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
>  	if (file->f_flags & O_DSYNC)
>  		pcm = _PAGE_CACHE_MODE_UC_MINUS;
>
> -	*vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) |
> -			     cachemode2protval(pcm));
> +	pgprot_set_cachemode(vma_prot, pcm);
>  	return 1;
>  }
>
> @@ -880,9 +885,7 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
>  				(unsigned long long)paddr,
>  				(unsigned long long)(paddr + size - 1),
>  				cattr_name(pcm));
> -			*vma_prot = __pgprot((pgprot_val(*vma_prot) &
> -					     (~_PAGE_CACHE_MASK)) |
> -					     cachemode2protval(pcm));
> +			pgprot_set_cachemode(vma_prot, pcm);
>  		}
>  		return 0;
>  	}
> @@ -907,9 +910,7 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
>  		 * We allow returning different type than the one requested in
>  		 * non strict case.
>  		 */
> -		*vma_prot = __pgprot((pgprot_val(*vma_prot) &
> -				      (~_PAGE_CACHE_MASK)) |
> -				     cachemode2protval(pcm));
> +		pgprot_set_cachemode(vma_prot, pcm);
>  	}
>
>  	if (memtype_kernel_map_sync(paddr, size, pcm) < 0) {
> @@ -1060,9 +1061,7 @@ int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
>  			return -EINVAL;
>  	}
>
> -	*prot = __pgprot((pgprot_val(*prot) & (~_PAGE_CACHE_MASK)) |
> -			 cachemode2protval(pcm));
> -
> +	pgprot_set_cachemode(prot, pcm);
>  	return 0;
>  }
>
> @@ -1073,10 +1072,8 @@ void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, pfn_t pfn)
>  	if (!pat_enabled())
>  		return;
>
> -	/* Set prot based on lookup */

We're losing a comment here but who cares, it's obvious what's happening.

>  	pcm = lookup_memtype(pfn_t_to_phys(pfn));
> -	*prot = __pgprot((pgprot_val(*prot) & (~_PAGE_CACHE_MASK)) |
> -			 cachemode2protval(pcm));
> +	pgprot_set_cachemode(prot, pcm);
>  }
>
>  /*
> @@ -1115,15 +1112,15 @@ void untrack_pfn_clear(struct vm_area_struct *vma)
>
>  pgprot_t pgprot_writecombine(pgprot_t prot)
>  {
> -	return __pgprot(pgprot_val(prot) |
> -				cachemode2protval(_PAGE_CACHE_MODE_WC));
> +	pgprot_set_cachemode(&prot, _PAGE_CACHE_MODE_WC);
> +	return prot;
>  }
>  EXPORT_SYMBOL_GPL(pgprot_writecombine);
>
>  pgprot_t pgprot_writethrough(pgprot_t prot)
>  {
> -	return __pgprot(pgprot_val(prot) |
> -				cachemode2protval(_PAGE_CACHE_MODE_WT));
> +	pgprot_set_cachemode(&prot, _PAGE_CACHE_MODE_WT);
> +	return prot;
>  }
>  EXPORT_SYMBOL_GPL(pgprot_writethrough);
>
> --
> 2.49.0
>