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Subject[patch] kvm: suppress KVM_SET_GSI_ROUTING allocation failure
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)
Call Trace:
__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0xf6/0x184 lib/dump_stack.c:51
warn_alloc+0x208/0x230 mm/page_alloc.c:2930
__vmalloc_node_range_memcg+0x510/0x670 mm/vmalloc.c:1711
__vmalloc_node_memcg mm/vmalloc.c:1751 [inline]
__vmalloc_node_memcg_flags mm/vmalloc.c:1788 [inline]
vmalloc+0x69/0x70 mm/vmalloc.c:1803
kvm_vm_ioctl+0x910/0x15e0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4153
vfs_ioctl fs/ioctl.c:44 [inline]
do_vfs_ioctl+0x842/0xee0 fs/ioctl.c:611
SYSC_ioctl fs/ioctl.c:626 [inline]
SyS_ioctl+0x94/0xc0 fs/ioctl.c:617
entry_SYSCALL_64_fastpath+0x12/0x17

If the vmalloc address space is fully depleted, the ioctl can gracefully
fail. Add __GFP_NOWARN to the allocation to suppress the warning.

Signed-off-by: David Rientjes <rientjes@google.com>
---
virt/kvm/kvm_main.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 001085b611ad..d0352dd45b95 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3063,7 +3063,8 @@ static long kvm_vm_ioctl(struct file *filp,
goto out;
if (routing.nr) {
r = -ENOMEM;
- entries = vmalloc(routing.nr * sizeof(*entries));
+ entries = __vmalloc(routing.nr * sizeof(*entries),
+ GFP_KERNEL | __GFP_NOWARN, PAGE_KERNEL);
if (!entries)
goto out;
r = -EFAULT;
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