linux-kernel - Re: [PATCH v1 09/11] x86/mm/pat: remove MEMTYPE_*

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Message-ID: <93c44cac-d4b0-4bf7-b2f4-ac957f53a485@lucifer.local>
Date: Tue, 6 May 2025 10:30:40 +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 09/11] x86/mm/pat: remove MEMTYPE_*_MATCH

On Mon, May 05, 2025 at 02:10:53PM +0200, David Hildenbrand wrote:
> On 28.04.25 22:23, Lorenzo Stoakes wrote:
> > On Fri, Apr 25, 2025 at 10:17:13AM +0200, David Hildenbrand wrote:
> > > The "memramp() shrinking" scenario no longer applies, so let's remove
> > > that now-unnecessary handling.
> >
> > I wonder if we could remove even more of the code here given the
> > simplifications here? But not a big deal.
>
> It might make sense to inline memtype_match().
>
> diff --git a/arch/x86/mm/pat/memtype_interval.c b/arch/x86/mm/pat/memtype_interval.c
> index 9d03f0dbc4715..e5844ed1311ed 100644
> --- a/arch/x86/mm/pat/memtype_interval.c
> +++ b/arch/x86/mm/pat/memtype_interval.c
> @@ -49,21 +49,6 @@ INTERVAL_TREE_DEFINE(struct memtype, rb, u64, subtree_max_end,
>  static struct rb_root_cached memtype_rbroot = RB_ROOT_CACHED;
> -static struct memtype *memtype_match(u64 start, u64 end)
> -{
> -       struct memtype *entry_match;
> -
> -       entry_match = interval_iter_first(&memtype_rbroot, start, end-1);
> -
> -       while (entry_match != NULL && entry_match->start < end) {
> -               if (entry_match->start == start && entry_match->end == end)
> -                       return entry_match;
> -               entry_match = interval_iter_next(entry_match, start, end-1);
> -       }
> -
> -       return NULL; /* Returns NULL if there is no match */
> -}
> -
>  static int memtype_check_conflict(u64 start, u64 end,
>                                   enum page_cache_mode reqtype,
>                                   enum page_cache_mode *newtype)
> @@ -119,14 +104,16 @@ int memtype_check_insert(struct memtype *entry_new, enum page_cache_mode *ret_ty
>  struct memtype *memtype_erase(u64 start, u64 end)
>  {
> -       struct memtype *entry_old;
> -
> -       entry_old = memtype_match(start, end);
> -       if (!entry_old)
> -               return ERR_PTR(-EINVAL);
> -
> -       interval_remove(entry_old, &memtype_rbroot);
> -       return entry_old;
> +       struct memtype *entry = interval_iter_first(&memtype_rbroot, start, end - 1);
> +
> +       while (entry && entry->start < end) {
> +               if (entry->start == start && entry->end == end) {
> +                       interval_remove(entry, &memtype_rbroot);
> +                       return entry;
> +               }
> +               entry = interval_iter_next(entry, start, end - 1);
> +       }
> +       return ERR_PTR(-EINVAL);
>  }
>  struct memtype *memtype_lookup(u64 addr)
>
>
> Thanks for all the review!

You're welcome :)

I _think_ I'm all caught up on my side of this review, ping me if there's
anything more you need from me.

>
> --
> Cheers,
>
> David / dhildenb
>

Cheers, Lorenzo