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Re: [RFC PATCH V3 09/11] HV/IOMMU: Enable swiotlb bounce buffer for Isolation VM

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)
-                 NULL,
+                 hyperv_swiotlb_detect,

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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