From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH] powerpc/32s: Speed up likely path of kuap_update_sr()
Date: Thu, 6 May 2021 13:27:31 +0000 (UTC) [thread overview]
Message-ID: <848f18d213b8341939add7302dc4ef80cc7a12e3.1620307636.git.christophe.leroy@csgroup.eu> (raw)
In most cases, kuap_update_sr() will update a single segment
register.
We know that first update will always be done, if there is no
segment register to update at all, kuap_update_sr() is not
called.
Avoid recurring calculations and tests in that case.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/include/asm/book3s/32/kup.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index 1670dfe9d4f1..c1f7c2e625a6 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -15,11 +15,13 @@ static inline void kuap_update_sr(u32 sr, u32 addr, u32 end)
{
addr &= 0xf0000000; /* align addr to start of segment */
barrier(); /* make sure thread.kuap is updated before playing with SRs */
- while (addr < end) {
+ for (;;) {
mtsr(sr, addr);
+ addr += 0x10000000; /* address of next segment */
+ if (addr >= end)
+ break;
sr += 0x111; /* next VSID */
sr &= 0xf0ffffff; /* clear VSID overflow */
- addr += 0x10000000; /* address of next segment */
}
isync(); /* Context sync required after mtsr() */
}
--
2.25.0
next reply other threads:[~2021-05-06 13:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 13:27 Christophe Leroy [this message]
2021-06-06 12:08 ` [PATCH] powerpc/32s: Speed up likely path of kuap_update_sr() Michael Ellerman
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