linux-kernel - RE: [PATCH V2 4/4] riscv: mm: Optimize TASK

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Date: Fri, 22 Dec 2023 11:52:39 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Guo Ren' <guoren@...nel.org>, Leonardo Bras <leobras@...hat.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"paul.walmsley@...ive.com" <paul.walmsley@...ive.com>, "palmer@...belt.com"
	<palmer@...belt.com>, "alexghiti@...osinc.com" <alexghiti@...osinc.com>,
	"charlie@...osinc.com" <charlie@...osinc.com>, "xiao.w.wang@...el.com"
	<xiao.w.wang@...el.com>, "david@...hat.com" <david@...hat.com>,
	"panqinglin2020@...as.ac.cn" <panqinglin2020@...as.ac.cn>,
	"rick.p.edgecombe@...el.com" <rick.p.edgecombe@...el.com>,
	"willy@...radead.org" <willy@...radead.org>, "bjorn@...osinc.com"
	<bjorn@...osinc.com>, "conor.dooley@...rochip.com"
	<conor.dooley@...rochip.com>, "cleger@...osinc.com" <cleger@...osinc.com>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>, Guo Ren
	<guoren@...ux.alibaba.com>
Subject: RE: [PATCH V2 4/4] riscv: mm: Optimize TASK_SIZE definition

From: Guo Ren
> Sent: 22 December 2023 11:25
...
> > > +#define TASK_SIZE    (is_compat_task() ? \
> > >                        TASK_SIZE_32 : TASK_SIZE_64)
> I would remove is_compat_task() in the next version because your patch
> contains that.

Does TASK_SIZE get used in access_ok() ?
If so the repeated expansion of that 'mess' will slow things down.

OTOH access_ok(ptr, len) can just check (ptr | (ptr + len)) < 0)
and rely on the page faults for everything else.

	David

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