Ensure pfn isn't already in use before assigning to addr[i]. Retry if
in use. The subsequent pfns were checked against the bitmap, but not
the initial selection.
This prevents some false positives on a machine with a small amount of
RAM where pfn collisions are more likely to be seen.
A Xen HVM first showed:
[ 3640.227939] CPA ffff88800869c000: bad pte 800000000869c163
[ 3640.227982] CPA ffff88800104e000: bad pte 800000000104e161
Testing this patch with a Xen PV guest with one 192MB of RAM showed
varying numbers of addresses like:
[ 2768.082971] CPA test 5 pfn 930d in use
Signed-off-by: Jason Andryuk <[email protected]>
---
This could infinite loop on a machine with a small amount of RAM - is
that worth handling? Just skip an in-use pfn instead?
---
arch/x86/mm/pat/cpa-test.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/pat/cpa-test.c b/arch/x86/mm/pat/cpa-test.c
index ad3c1feec990..bbf337e3e246 100644
--- a/arch/x86/mm/pat/cpa-test.c
+++ b/arch/x86/mm/pat/cpa-test.c
@@ -136,7 +136,14 @@ static int pageattr_test(void)
failed += print_split(&sa);
for (i = 0; i < NTEST; i++) {
- unsigned long pfn = get_random_u32_below(max_pfn_mapped);
+ unsigned long pfn;
+
+ retry:
+ pfn = get_random_u32_below(max_pfn_mapped);
+ if (test_bit(pfn, bm)) {
+ pr_debug("CPA test %d pfn %lx in use\n", i, pfn);
+ goto retry;
+ }
addr[i] = (unsigned long)__va(pfn << PAGE_SHIFT);
len[i] = get_random_u32_below(NPAGES);
--
2.43.0