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[PowerPC64LE] Implement endian-independent dword atomic PTE lock.

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It's much easier to implement this in an endian-independent way when we
don't also have to worry about masking half of the dword off.

Given that this code ran on a machine that ran a poudriere bulk with no
kernel oddities, I am relatively certain it is correctly implemented. ;)

This should be a minor performance boost on BE as well.

Sponsored by:	Tag1 Consulting, Inc.
This commit is contained in:
Brandon Bergren 2020-09-23 01:33:54 +00:00
parent f475e00fb3
commit d418d3f616
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=366046
1 changed files with 33 additions and 1 deletions
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34
sys/powerpc/aim/moea64_native.c
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@ -633,14 +633,45 @@ static int
atomic_pte_lock(volatile struct lpte *pte, uint64_t bitmask, uint64_t *oldhi)
{
int ret;
#ifdef __powerpc64__
uint64_t temp;
#else
uint32_t oldhihalf;
#endif
/*
* Note: in principle, if just the locked bit were set here, we
* could avoid needing the eviction lock. However, eviction occurs
* so rarely that it isn't worth bothering about in practice.
*/
#ifdef __powerpc64__
/*
* Note: Success of this sequence has the side effect of invalidating
* the PTE, as we are setting it to LPTE_LOCKED and discarding the
* other bits, including LPTE_V.
*/
__asm __volatile (
"1:\tldarx %1, 0, %3\n\t" /* load old value */
"and. %0,%1,%4\n\t" /* check if any bits set */
"bne 2f\n\t" /* exit if any set */
"stdcx. %5, 0, %3\n\t" /* attempt to store */
"bne- 1b\n\t" /* spin if failed */
"li %0, 1\n\t" /* success - retval = 1 */
"b 3f\n\t" /* we've succeeded */
"2:\n\t"
"stdcx. %1, 0, %3\n\t" /* clear reservation (74xx) */
"li %0, 0\n\t" /* failure - retval = 0 */
"3:\n\t"
: "=&r" (ret), "=&r"(temp), "=m" (pte->pte_hi)
: "r" ((volatile char *)&pte->pte_hi),
"r" (htobe64(bitmask)), "r" (htobe64(LPTE_LOCKED)),
"m" (pte->pte_hi)
: "cr0", "cr1", "cr2", "memory");
*oldhi = be64toh(temp);
#else
/*
* This code is used on bridge mode only.
*/
__asm __volatile (
"1:\tlwarx %1, 0, %3\n\t" /* load old value */
"and. %0,%1,%4\n\t" /* check if any bits set */
@ -660,6 +691,7 @@ atomic_pte_lock(volatile struct lpte *pte, uint64_t bitmask, uint64_t *oldhi)
: "cr0", "cr1", "cr2", "memory");
*oldhi = (pte->pte_hi & 0xffffffff00000000ULL) | oldhihalf;
#endif
return (ret);
}