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Date:   Wed, 14 Apr 2021 17:50:16 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Tianyu Lan <ltykernel@gmail.com>
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Subject: Re: [Resend RFC PATCH V2 11/12] HV/Netvsc: Add Isolation VM
 support for netvsc driver
Message-ID: <20210414155016.GE32045@lst.de>
References: <20210414144945.3460554-1-ltykernel@gmail.com> <20210414144945.3460554-12-ltykernel@gmail.com>
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> +struct dma_range {
> +	dma_addr_t dma;
> +	u32 mapping_size;
> +};

That's a rather generic name that is bound to create a conflict sooner
or later.

>  #include "hyperv_net.h"
>  #include "netvsc_trace.h"
> +#include "../../hv/hyperv_vmbus.h"

Please move public interfaces out of the private header rather than doing
this.

> +	if (hv_isolation_type_snp()) {
> +		area = get_vm_area(buf_size, VM_IOREMAP);

Err, no.  get_vm_area is private a for a reason.

> +		if (!area)
> +			goto cleanup;
> +
> +		vaddr = (unsigned long)area->addr;
> +		for (i = 0; i < buf_size / HV_HYP_PAGE_SIZE; i++) {
> +			extra_phys = (virt_to_hvpfn(net_device->recv_buf + i * HV_HYP_PAGE_SIZE)
> +				<< HV_HYP_PAGE_SHIFT) + ms_hyperv.shared_gpa_boundary;
> +			ret |= ioremap_page_range(vaddr + i * HV_HYP_PAGE_SIZE,
> +					   vaddr + (i + 1) * HV_HYP_PAGE_SIZE,
> +					   extra_phys, PAGE_KERNEL_IO);
> +		}
> +
> +		if (ret)
> +			goto cleanup;

And this is not something a driver should ever do.  I think you are badly
reimplementing functionality that should be in the dma coherent allocator
here.