Currently dma_bitsize is zero by default on single NUMA node machines.
This makes all alloc_domheap_pages() calls with MEMF_no_dma return NULL.
There is only 1 user of MEMF_no_dma: dom0_memflags, which are used
during memory allocation for Dom0. Failing allocation with default
dom0_memflags is especially severe for the PV Dom0 case: it makes
alloc_chunk() to use suboptimal 2MB allocation algorithm with a search
for higher memory addresses.
This can lead to the NMI watchdog timeout during PV Dom0 construction
on some machines, which can be worked around by specifying "dma_bits"
in Xen's cmdline manually.
Fix the issue by ignoring MEMF_no_dma in cases when dma_bitsize is zero,
which means there is no DMA zone. This shouldn't cause any issues for
Dom0 because alloc_heap_pages() will first use higher memory addresses
for satisfying memory allocation requests.
Signed-off-by: Sergey Dyasli <sergey.dya...@citrix.com>
---
v2:
- A different approach as suggested by Jan, with wording changes
---
CC: Andrew Cooper <andrew.coop...@citrix.com>
CC: Jan Beulich <jbeul...@suse.com>
CC: Julien Grall <julien.gr...@arm.com>
CC: Wei Liu <wei.l...@citrix.com>
CC: Boris Ostrovsky <boris.ostrov...@oracle.com>
CC: George Dunlap <george.dun...@eu.citrix.com>
CC: Roger Pau Monné <roger....@citrix.com>
---
xen/common/page_alloc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 37a52aaa0d..f71d3bb7a1 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2314,7 +2314,9 @@ struct page_info *alloc_domheap_pages(
return NULL;
}
- if ( dma_bitsize && ((dma_zone = bits_to_zone(dma_bitsize)) < zone_hi) )
+ if ( !dma_bitsize )
+ memflags &= ~MEMF_no_dma;
+ else if ( (dma_zone = bits_to_zone(dma_bitsize)) < zone_hi )
pg = alloc_heap_pages(dma_zone + 1, zone_hi, order, memflags, d);
if ( (pg == NULL) &&
--
2.17.1
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