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SubjectRe: [PATCH] KVM: x86: Fix warning due to implicit truncation on 32-bit KVM
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On 05/03/20 01:24, Sean Christopherson wrote:
> Explicitly cast the integer literal to an unsigned long when stuffing a
> non-canonical value into the host virtual address during private memslot
> deletion. The explicit cast fixes a warning that gets promoted to an
> error when running with KVM's newfangled -Werror setting.
>
> arch/x86/kvm/x86.c:9739:9: error: large integer implicitly truncated
> to unsigned type [-Werror=overflow]
>
> Fixes: a3e967c0b87d3 ("KVM: Terminate memslot walks via used_slots"
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/x86.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ba4d476b79ad..fa03f31ab33c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9735,8 +9735,12 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size)
> if (!slot || !slot->npages)
> return 0;
>
> - /* Stuff a non-canonical value to catch use-after-delete. */
> - hva = 0xdeadull << 48;
> + /*
> + * Stuff a non-canonical value to catch use-after-delete. This
> + * ends up being 0 on 32-bit KVM, but there's no better
> + * alternative.
> + */
> + hva = (unsigned long)(0xdeadull << 48);
> old_npages = slot->npages;
> }
>
>

Queued, thanks.

Paolo

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