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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Sat, 15 Aug 2015 01:41:26 +0200
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Subject: Re: [Qemu-devel] [PATCH v2 3/6] hw/block/nvme.c: Use pow2ceil()
 rather than hand-calculation
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To: Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Keith Busch <keith.busch@intel.com>, patches@linaro.org, qemu-block@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>



On 24/07/2015 14:33, Peter Maydell wrote:
> Use pow2ceil() to round up to the next power of 2, rather
> than an inline calculation.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/block/nvme.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/block/nvme.c b/hw/block/nvme.c
> index 40d4880..5da41b2 100644
> --- a/hw/block/nvme.c
> +++ b/hw/block/nvme.c
> @@ -805,7 +805,7 @@ static int nvme_init(PCIDevice *pci_dev)
>  
>      n->num_namespaces = 1;
>      n->num_queues = 64;
> -    n->reg_size = 1 << qemu_fls(0x1004 + 2 * (n->num_queues + 1) * 4);
> +    n->reg_size = pow2ceil(0x1004 + 2 * (n->num_queues + 1) * 4);

The pre-patch version only worked because the expression was never a
power of two.  Won't miss the cleverness. :)

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

>      n->ns_size = bs_size / (uint64_t)n->num_namespaces;
>  
>      n->namespaces = g_new0(NvmeNamespace, n->num_namespaces);
>