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Re: [PATCH v4 13/21] IOMMU/x86: prefill newly allocate page tables
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 20 May 2022 13:11:16 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Fri, 20 May 2022 11:11:26 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 20.05.2022 12:47, Roger Pau Monné wrote:
> On Thu, May 19, 2022 at 02:12:04PM +0200, Jan Beulich wrote:
>> On 06.05.2022 13:16, Roger Pau Monné wrote:
>>> On Mon, Apr 25, 2022 at 10:40:55AM +0200, Jan Beulich wrote:
>>>> --- a/xen/drivers/passthrough/amd/iommu_map.c
>>>> +++ b/xen/drivers/passthrough/amd/iommu_map.c
>>>> @@ -115,7 +115,19 @@ static void set_iommu_ptes_present(unsig
>>>>
>>>> while ( nr_ptes-- )
>>>> {
>>>> - set_iommu_pde_present(pde, next_mfn, 0, iw, ir);
>>>> + ASSERT(!pde->next_level);
>>>> + ASSERT(!pde->u);
>>>> +
>>>> + if ( pde > table )
>>>> + ASSERT(pde->ign0 == find_first_set_bit(pde - table));
>>>> + else
>>>> + ASSERT(pde->ign0 == PAGE_SHIFT - 3);
>>>
>>> I think PAGETABLE_ORDER would be clearer here.
>>
>> I disagree - PAGETABLE_ORDER is a CPU-side concept. It's not used anywhere
>> in IOMMU code afaics.
>
> Isn't PAGE_SHIFT also a CPU-side concept in the same way? I'm not
> sure what's the rule for declaring that PAGE_SHIFT is fine to use in
> IOMMU code but not PAGETABLE_ORDER.
Hmm, yes and no. But for consistency with other IOMMU code I may want
to switch to PAGE_SHIFT_4K.
Jan
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