Re: [PATCH V3 3/5] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM

[Tianyu Lan <ltykernel@xxxxxxxxx>]

On 12/4/2021 3:17 AM, Michael Kelley (LINUX) wrote:
> > +static void __init hyperv_iommu_swiotlb_init(void)
> > +{
> > +       unsigned long hyperv_io_tlb_size;
> > +       void *hyperv_io_tlb_start;
> > +
> > +       /*
> > +        * Allocate Hyper-V swiotlb bounce buffer at early place
> > +        * to reserve large contiguous memory.
> > +        */
> > +       hyperv_io_tlb_size = swiotlb_size_or_default();
> > +       hyperv_io_tlb_start = memblock_alloc(hyperv_io_tlb_size, PAGE_SIZE);
> > +
> > +       if (!hyperv_io_tlb_start)
> > +               pr_warn("Fail to allocate Hyper-V swiotlb buffer.\n");
> In the error case, won't swiotlb_init_with_tlb() end up panic'ing when
> it tries to zero out the memory?   The only real choice here is to
> return immediately after printing the message, and not call
> swiotlb_init_with_tlb().
Yes, agree. Will update.