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Re: [Qemu-devel] [PATCH] intel_iommu: fix and simplify size calculation
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] intel_iommu: fix and simplify size calculation in process_device_iotlb_desc() |
Date: |
Fri, 20 Jan 2017 14:38:52 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 |
On 20/01/2017 07:35, Jason Wang wrote:
> We don't use 1ULL which is wrong during size calculation. Fix it, and
> while at it, switch to use cto64() and adds a comments to make it
> simpler and easier to be understood.
>
> Reported-by: Paolo Bonzini <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Signed-off-by: Jason Wang <address@hidden>
> ---
> hw/i386/intel_iommu.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index ec62239..3270fb9 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -1485,8 +1485,16 @@ static bool
> vtd_process_device_iotlb_desc(IntelIOMMUState *s,
> goto done;
> }
>
> + /* According to ATS spec table 2.4:
> + * S = 0, bits 15:12 = xxxx range size: 4K
> + * S = 1, bits 15:12 = xxx0 range size: 8K
> + * S = 1, bits 15:12 = xx01 range size: 16K
> + * S = 1, bits 15:12 = x011 range size: 32K
> + * S = 1, bits 15:12 = 0111 range size: 64K
> + * ...
> + */
> if (size) {
> - sz = 1 << (ctz64(~(addr | (VTD_PAGE_MASK_4K - 1))) + 1);
> + sz = (VTD_PAGE_SIZE * 2) << cto64(addr >> VTD_PAGE_SHIFT);
> addr &= ~(sz - 1);
> } else {
> sz = VTD_PAGE_SIZE;
>
Reviewed-by: Paolo Bonzini <address@hidden>