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From: Maxime Coquelin <maxime.coquelin@redhat.com>
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Date: Fri, 6 Oct 2017 12:28:22 +0200
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Subject: Re: [Qemu-devel] [REBASED 1/2] exec: add page_mask for
 flatview_do_translate
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To: peterx@redhat.com, pbonzini@redhat.com, mst@redhat.com, jasowang@redhat.com, qemu-devel@nongnu.org
Cc: qemu-stable@nongnu.org



On 10/05/2017 07:13 PM, Maxime Coquelin wrote:
>   static MemoryRegionSection flatview_do_translate(FlatView *fv,
>                                                    hwaddr addr,
>                                                    hwaddr *xlat,
> -                                                 hwaddr *plen,
> +                                                 hwaddr *plen_out,
> +                                                 hwaddr *page_mask_out,
>                                                    bool is_write,
>                                                    bool is_mmio,
>                                                    AddressSpace **target_as)
> @@ -480,11 +498,17 @@ static MemoryRegionSection flatview_do_translate(FlatView *fv,
>       MemoryRegionSection *section;
>       IOMMUMemoryRegion *iommu_mr;
>       IOMMUMemoryRegionClass *imrc;
> +    hwaddr page_mask = TARGET_PAGE_MASK;

There is a bug here that breaks the case when iommu is not enabled in
kernel cmdline. In this case returned page_mask is the about init value.

But TARGET_PAGE_MASK actually represents the pfn mask, from cpu-all.h:
#define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS)
#define TARGET_PAGE_MASK ~(TARGET_PAGE_SIZE - 1)
With TARGET_PAGE_SIZE being 12 on x86.

What we expect here as init value is its complement, i.e. 0xfff on x86.

I'll send a follow-up patch in a short while.

Regards,
Maxime