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From: Yeoreum Yun <yeoreum.yun@arm.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: catalin.marinas@arm.com, will@kernel.org,
	akpm@linux-foundation.org, david@kernel.org,
	kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com,
	dev.jain@arm.com, yang@os.amperecomputing.com,
	chaitanyas.prakash@arm.com, bigeasy@linutronix.de,
	clrkwllms@kernel.org, rostedt@goodmis.org,
	lorenzo.stoakes@oracle.com, ardb@kernel.org, jackmanb@google.com,
	vbabka@suse.cz, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev
Subject: Re: [PATCH v2 2/2] arm64: mmu: avoid allocating pages while installing ng-mapping for KPTI
Date: Thu, 18 Dec 2025 08:37:07 +0000	[thread overview]
Message-ID: <aUO9M/oN+nx3nfW+@e129823.arm.com> (raw)
In-Reply-To: <72aaa252-6ee6-4353-84ee-b6e10e9920c6@arm.com>

[...]
> > I think it would be better to use only __GFP_HIGH in here since
> > when kpti_install_ng_mappings() is called, "kswpd" doesn't created yet.
> > and to allocate page with assurance, It would be good to use
> > min_reserved to.
> >
> > Am I missing something?
>
> Personally I think we should just use "GFP_KERNEL | __GFP_ZERO". Anything else
> would make this allocation look special, which it is not. If we fail to allocate
> at this point in boot, we have bigger problems.

But I'm not sure *HOW effective* to use GFP_KERNEL in here.
Since it's before the any filesystem inited.
IOW, in this context, almost there would be no *page cache*
and I think it seems meaningless to use "GFP_KERNEL" and "direct
reclaim"

So to get success for allocation, __GFP_HIGH | _GFP_ZERO seems much
better.

Thanks


--
Sincerely,
Yeoreum Yun

  reply	other threads:[~2025-12-18  8:38 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-12-17 18:20 [PATCH v2 0/2] fix wrong usage of memory allocation APIs under PREEMPT_RT in arm64 Yeoreum Yun
2025-12-17 18:20 ` [PATCH v2 1/2] arm64: mmu: don't allocate page while spliting linear mapping Yeoreum Yun
2025-12-18  8:23   ` David Hildenbrand (Red Hat)
2025-12-18  9:08     ` Yeoreum Yun
2025-12-18 14:22   ` Ryan Roberts
2025-12-18 15:01     ` Yeoreum Yun
2025-12-18 15:42       ` Ryan Roberts
2025-12-18 15:54         ` Yeoreum Yun
2025-12-17 18:20 ` [PATCH v2 2/2] arm64: mmu: avoid allocating pages while installing ng-mapping for KPTI Yeoreum Yun
2025-12-17 19:03   ` Ryan Roberts
2025-12-17 19:09     ` Yeoreum Yun
2025-12-18  8:34       ` Ryan Roberts
2025-12-18  8:37         ` Yeoreum Yun [this message]
2025-12-18  8:46           ` David Hildenbrand (Red Hat)
2025-12-18  9:31             ` Yeoreum Yun
2025-12-18  9:41               ` David Hildenbrand (Red Hat)
2025-12-18 10:07                 ` Yeoreum Yun
2025-12-18  7:51     ` Vlastimil Babka
2025-12-18  8:32       ` Ryan Roberts

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