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SubjectRe: [patch] kvm: suppress KVM_SET_GSI_ROUTING allocation failure
On Thu 08-02-18 13:35:08, David Rientjes wrote:
> The KVM_SET_GSI_ROUTING ioctl does a vmalloc() of
> sizeof(struct kvm_irq_routing_entry) multiplied by a user-supplied value.
> This can be up to 4096 entries on architectures such as arm64 and s390
> (and the upper bound may be increased on s390 eventually).
>
> This can produce a vmalloc allocation failure warning:
>
> vmalloc: allocation failure: 0 bytes, mode:0x24000c2(GFP_KERNEL|__GFP_HIGHMEM)

I am not arguing about the kvm change but do we actaully want to warn
for 0 sized allocations? This just doesn't make much sense to me.
In other words don't we want this?

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 673942094328..c5d832510c54 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1748,7 +1748,9 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
unsigned long real_size = size;

size = PAGE_ALIGN(size);
- if (!size || (size >> PAGE_SHIFT) > totalram_pages)
+ if (!size)
+ return NULL;
+ if ((size >> PAGE_SHIFT) > totalram_pages)
goto fail;

area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
--
Michal Hocko
SUSE Labs
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