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powerpc/32s: Speed up likely path of kuap_update_sr()

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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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/848f18d213b8341939add7302dc4ef80cc7a12e3.1620307636.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-05-06 13:27:31 +00:00 committed by Michael Ellerman
parent 0441729e16
commit 8af8d72dc5
1 changed files with 4 additions and 2 deletions
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6
arch/powerpc/include/asm/book3s/32/kup.h
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@ -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() */
}