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SubjectRe: [patch] kvm: suppress KVM_SET_GSI_ROUTING allocation failure
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On 08/02/2018 22:35, 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)
> 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>

Queued, thanks.

Paolo

> ---
> 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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