linux-kernel - Re: [PATCH v2 08/11] x86/mm/pat: remove MEMTYPE_*

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Message-ID: <4ff30707-99ea-472a-9f16-517f52d7729a@redhat.com>
Date: Thu, 15 May 2025 16:10:34 +0200
From: David Hildenbrand <david@...hat.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 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>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
 Pedro Falcato <pfalcato@...e.de>, Peter Xu <peterx@...hat.com>,
 Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2 08/11] x86/mm/pat: remove MEMTYPE_*_MATCH

On 14.05.25 19:53, David Hildenbrand wrote:
> On 13.05.25 19:48, Liam R. Howlett wrote:
>> * David Hildenbrand <david@...hat.com> [250512 08:34]:
>>> The "memramp() shrinking" scenario no longer applies, so let's remove
>>> that now-unnecessary handling.
>>>
>>> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
>>> Acked-by: Ingo Molnar <mingo@...nel.org> # x86 bits
>>> Signed-off-by: David Hildenbrand <david@...hat.com>
>>
>> small comment, but this looks good.
>>
>> Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> 
> Thanks!
> 
>>
>>> ---
>>>    arch/x86/mm/pat/memtype_interval.c | 44 ++++--------------------------
>>>    1 file changed, 6 insertions(+), 38 deletions(-)
>>>
>>> diff --git a/arch/x86/mm/pat/memtype_interval.c b/arch/x86/mm/pat/memtype_interval.c
>>> index 645613d59942a..9d03f0dbc4715 100644
>>> --- a/arch/x86/mm/pat/memtype_interval.c
>>> +++ b/arch/x86/mm/pat/memtype_interval.c
>>> @@ -49,26 +49,15 @@ INTERVAL_TREE_DEFINE(struct memtype, rb, u64, subtree_max_end,
>>>    
>>>    static struct rb_root_cached memtype_rbroot = RB_ROOT_CACHED;
>>>    
>>> -enum {
>>> -	MEMTYPE_EXACT_MATCH	= 0,
>>> -	MEMTYPE_END_MATCH	= 1
>>> -};
>>> -
>>> -static struct memtype *memtype_match(u64 start, u64 end, int match_type)
>>> +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) {
>>
>> I think this could use interval_tree_for_each_span() instead.
> 
> Fancy, let me look at this. Probably I'll send another patch on top of
> this series to do that conversion. (as you found, patch #9 moves that code)

Hmmm, I think interval_tree_for_each_span() does not apply here.

Unless I am missing something important, interval_tree_for_each_span() 
does not work in combination with INTERVAL_TREE_DEFINE where we want to 
use a custom type as tree nodes (-> struct memtype).

interval_tree_for_each_span() only works with the basic "struct 
interval_tree_node" implementation ... which is probably also why there 
are only a handful (3) of interval_tree_for_each_span() users, all in 
iommufd context?

But staring at interval_tree.h vs. interval_tree_generic.h, I am a bit 
confused ...

-- 
Cheers,

David / dhildenb