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vm: Don't break vm reserv that can't meet align reqs

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Function vm_reserv_test_contig has incorrectly used its alignment
and boundary parameters to find a well-positioned range of empty pages
in a reservation.  Consequently, a reservation could be broken
mistakenly when it was unable to provide a satisfactory set of pages.

Rename the function, correct the errors, and add assertions to detect
the error in case it appears again.

Reviewed by:	alc, markj
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D33344
This commit is contained in:
Doug Moore 2021-12-16 12:20:56 -06:00
parent 02732f945e
commit 6f1c890827
1 changed files with 65 additions and 29 deletions
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94
sys/vm/vm_reserv.c
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@ -1233,25 +1233,29 @@ vm_reserv_reclaim_inactive(int domain)
/*
* Determine whether this reservation has free pages that satisfy the given
* request for contiguous physical memory. Start searching from the lower
* bound, defined by low_index.
* bound, defined by lo, and stop at the upper bound, hi. Return the index
* of the first satisfactory free page, or -1 if none is found.
*/
static bool
vm_reserv_test_contig(vm_reserv_t rv, u_long npages, vm_paddr_t low,
vm_paddr_t high, u_long alignment, vm_paddr_t boundary)
static int
vm_reserv_find_contig(vm_reserv_t rv, int npages, int lo,
int hi, int ppn_align, int ppn_bound)
{
vm_paddr_t pa, size;
u_long changes;
int bitpos, bits_left, i, hi, lo, n;
int bitpos, bits_left, i, n;
vm_reserv_assert_locked(rv);
size = npages << PAGE_SHIFT;
pa = VM_PAGE_TO_PHYS(&rv->pages[0]);
lo = (pa < low) ?
((low + PAGE_MASK - pa) >> PAGE_SHIFT) : 0;
KASSERT(npages <= VM_LEVEL_0_NPAGES - 1,
("%s: Too many pages", __func__));
KASSERT(ppn_bound <= VM_LEVEL_0_NPAGES,
("%s: Too big a boundary for reservation size", __func__));
KASSERT(npages <= ppn_bound,
("%s: Too many pages for given boundary", __func__));
KASSERT(ppn_align != 0 && powerof2(ppn_align),
("ppn_align is not a positive power of 2"));
KASSERT(ppn_bound != 0 && powerof2(ppn_bound),
("ppn_bound is not a positive power of 2"));
i = lo / NBPOPMAP;
changes = rv->popmap[i] | ((1UL << (lo % NBPOPMAP)) - 1);
hi = (pa + VM_LEVEL_0_SIZE > high) ?
((high + PAGE_MASK - pa) >> PAGE_SHIFT) : VM_LEVEL_0_NPAGES;
n = hi / NBPOPMAP;
bits_left = hi % NBPOPMAP;
hi = lo = -1;
@ -1276,25 +1280,20 @@ vm_reserv_test_contig(vm_reserv_t rv, u_long npages, vm_paddr_t low,
continue;
}
hi = NBPOPMAP * i + bitpos;
pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
if ((pa & (alignment - 1)) != 0) {
if (lo < roundup2(lo, ppn_align)) {
/* Skip to next aligned page. */
lo += (((pa - 1) | (alignment - 1)) + 1) >>
PAGE_SHIFT;
lo = roundup2(lo, ppn_align);
if (lo >= VM_LEVEL_0_NPAGES)
return (false);
pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
return (-1);
}
if (((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0) {
if (lo + npages > roundup2(lo, ppn_bound)) {
/* Skip to next boundary-matching page. */
lo += (((pa - 1) | (boundary - 1)) + 1) >>
PAGE_SHIFT;
lo = roundup2(lo, ppn_bound);
if (lo >= VM_LEVEL_0_NPAGES)
return (false);
pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
return (-1);
}
if (lo * PAGE_SIZE + size <= hi * PAGE_SIZE)
return (true);
if (lo + npages <= hi)
return (lo);
lo = hi;
}
if (++i < n)
@ -1303,7 +1302,7 @@ vm_reserv_test_contig(vm_reserv_t rv, u_long npages, vm_paddr_t low,
changes = bits_left == 0 ? -1UL :
(rv->popmap[n] | (-1UL << bits_left));
else
return (false);
return (-1);
}
}
@ -1320,12 +1319,32 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm_paddr_t low,
struct vm_reserv_queue *queue;
vm_paddr_t pa, size;
vm_reserv_t marker, rv, rvn;
int hi, lo, posn, ppn_align, ppn_bound;
KASSERT(npages > 0, ("npages is 0"));
KASSERT(powerof2(alignment), ("alignment is not a power of 2"));
KASSERT(powerof2(boundary), ("boundary is not a power of 2"));
if (npages > VM_LEVEL_0_NPAGES - 1)
return (false);
size = npages << PAGE_SHIFT;
/*
* Ensure that a free range starting at a boundary-multiple
* doesn't include a boundary-multiple within it. Otherwise,
* no boundary-constrained allocation is possible.
*/
if (size > boundary)
return (false);
marker = &vm_rvd[domain].marker;
queue = &vm_rvd[domain].partpop;
size = npages << PAGE_SHIFT;
/*
* Compute shifted alignment, boundary values for page-based
* calculations. Constrain to range [1, VM_LEVEL_0_NPAGES] to
* avoid overflow.
*/
ppn_align = (int)(ulmin(ulmax(PAGE_SIZE, alignment),
VM_LEVEL_0_SIZE) >> PAGE_SHIFT);
ppn_bound = (int)(MIN(MAX(PAGE_SIZE, boundary),
VM_LEVEL_0_SIZE) >> PAGE_SHIFT);
vm_reserv_domain_scan_lock(domain);
vm_reserv_domain_lock(domain);
@ -1339,6 +1358,10 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm_paddr_t low,
/* This entire reservation is too high; go to next. */
continue;
}
if ((pa & (alignment - 1)) != 0) {
/* This entire reservation is unaligned; go to next. */
continue;
}
if (vm_reserv_trylock(rv) == 0) {
TAILQ_INSERT_AFTER(queue, rv, marker, partpopq);
@ -1356,8 +1379,21 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm_paddr_t low,
TAILQ_REMOVE(queue, marker, partpopq);
}
vm_reserv_domain_unlock(domain);
if (vm_reserv_test_contig(rv, npages, low, high,
alignment, boundary)) {
lo = (pa >= low) ? 0 :
(int)((low + PAGE_MASK - pa) >> PAGE_SHIFT);
hi = (pa + VM_LEVEL_0_SIZE <= high) ? VM_LEVEL_0_NPAGES :
(int)((high - pa) >> PAGE_SHIFT);
posn = vm_reserv_find_contig(rv, (int)npages, lo, hi,
ppn_align, ppn_bound);
if (posn >= 0) {
pa = VM_PAGE_TO_PHYS(&rv->pages[posn]);
KASSERT((pa & (alignment - 1)) == 0,
("%s: adjusted address does not align to %lx",
__func__, alignment));
KASSERT(((pa ^ (pa + size - 1)) & -boundary) == 0,
("%s: adjusted address spans boundary to %lx",
__func__, boundary));
vm_reserv_domain_scan_unlock(domain);
vm_reserv_reclaim(rv);
vm_reserv_unlock(rv);