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bcm64: enter page tables in mmutop *AFTER* switching asid in mmuswitch()

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there was a small window between modifying mmutop and switching the
asid where the core could bring in the new entries under the old asid
into the tlb due to speculation / prefetching.

this change moves the entering of the page tables into mmutop after
setttbr() to prevent this scenario.

due to us switching to the resereved asid 0 on procsave()->putasid(),
the only asid that could have potentially been poisoned would be asid 0
which does not have any user mappings. so this did not show any noticable
effect.
This commit is contained in:
cinap_lenrek 2019-09-14 14:02:34 +02:00
parent ca2f1c07f2
commit acab8881bc
1 changed files with 5 additions and 5 deletions
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10
sys/src/9/bcm64/mmu.c
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@ -499,15 +499,15 @@ mmuswitch(Proc *p)
p->newtlb = 0;
}
for(t = p->mmuhead[PTLEVELS-1]; t != nil; t = t->next){
va = t->va;
m->mmutop[PTLX(va, PTLEVELS-1)] = t->pa | PTEVALID | PTETABLE;
}
if(allocasid(p))
flushasid((uvlong)p->asid<<48);
setttbr((uvlong)p->asid<<48 | PADDR(m->mmutop));
for(t = p->mmuhead[PTLEVELS-1]; t != nil; t = t->next){
va = t->va;
m->mmutop[PTLX(va, PTLEVELS-1)] = t->pa | PTEVALID | PTETABLE;
}
}
void