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Ensure that a thread stays on same CPU when calculating per CPU

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TLB shootdown requirements. Otherwise a CPU may not get the needed
TLB invalidation.

The PTE valid and access flags can not be used here to avoid TLB
shootdowns unless sf->cpumask == all_cpus.
( Otherwise some CPUs may still hold an even older entry in the TLB)
Since sf_buf_alloc mappings are normally always used this is
also not really useful and presetting accessed and modified
allows the CPU to speculatively load the entry into the TLB.

Both bugs can cause random data corruption.

MFC after:	3 days
This commit is contained in:
ups 2005-10-12 01:41:48 +00:00
parent 1bf7a68287
commit 06cb0fb4c0
1 changed files with 15 additions and 15 deletions
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30
sys/i386/i386/vm_machdep.c
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@ -63,6 +63,7 @@ __FBSDID("$FreeBSD$");
#include <sys/proc.h>
#include <sys/sf_buf.h>
#include <sys/smp.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
@ -672,6 +673,7 @@ sf_buf_alloc(struct vm_page *m, int flags)
nsfbufspeak = imax(nsfbufspeak, nsfbufsused);
}
#ifdef SMP
sched_pin();
cpumask = PCPU_GET(cpumask);
if ((sf->cpumask & cpumask) == 0) {
sf->cpumask |= cpumask;
@ -686,6 +688,8 @@ sf_buf_alloc(struct vm_page *m, int flags)
mtx_unlock_spin(&smp_ipi_mtx);
}
}
sched_unpin();
#endif
goto done;
}
@ -716,28 +720,24 @@ sf_buf_alloc(struct vm_page *m, int flags)
/*
* Update the sf_buf's virtual-to-physical mapping, flushing the
* virtual address from the TLB only if the PTE implies that the old
* mapping has been used. Since the reference count for the sf_buf's
* old mapping was zero, that mapping is not currently in use.
* Consequently, there is no need to exchange the old and new PTEs
* atomically, even under PAE.
* virtual address from the TLB. Since the reference count for
* the sf_buf's old mapping was zero, that mapping is not
* currently in use. Consequently, there is no need to exchange
* the old and new PTEs atomically, even under PAE.
*/
ptep = vtopte(sf->kva);
opte = *ptep;
*ptep = VM_PAGE_TO_PHYS(m) | pgeflag | PG_RW | PG_V;
*ptep = VM_PAGE_TO_PHYS(m) | pgeflag | PG_RW | PG_V | PG_A | PG_M;
#ifdef SMP
if (flags & SFB_CPUPRIVATE) {
if ((opte & (PG_A | PG_V)) == (PG_A | PG_V)) {
sf->cpumask = PCPU_GET(cpumask);
invlpg(sf->kva);
} else
sf->cpumask = all_cpus;
sf->cpumask = PCPU_GET(cpumask);
invlpg(sf->kva);
goto done;
} else
sf->cpumask = all_cpus;
}
sf->cpumask = all_cpus;
#endif
if ((opte & (PG_A | PG_V)) == (PG_A | PG_V))
pmap_invalidate_page(kernel_pmap, sf->kva);
pmap_invalidate_page(kernel_pmap, sf->kva);
done:
mtx_unlock(&sf_buf_lock);
return (sf);