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SubjectRe: [RFC PATCH V3 09/11] HV/IOMMU: Enable swiotlb bounce buffer for Isolation VM
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Hi Boris:
Thanks for your review.

On 6/2/2021 9:16 AM, Boris Ostrovsky wrote:
>
> On 5/30/21 11:06 AM, Tianyu Lan wrote:
>> @@ -91,6 +92,6 @@ int pci_xen_swiotlb_init_late(void)
>> EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
>>
>> IOMMU_INIT_FINISH(2,
>> - NULL,
>> + hyperv_swiotlb_detect,
>> pci_xen_swiotlb_init,
>> NULL);
>
>
> Could you explain this change?

Hyper-V allocates its own swiotlb bounce buffer and the default
swiotlb buffer should not be allocated. swiotlb_init() in
pci_swiotlb_init() is to allocate default swiotlb buffer.
To achieve this, put hyperv_swiotlb_detect() as the first entry in the
iommu_table_entry list. The detect loop in the pci_iommu_alloc() will
exit once hyperv_swiotlb_detect() is called in Hyper-V VM and other
iommu_table_entry callback will not be called.

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