Re: [PATCH v9 05/13] iommu/amd: Add function copy_dev_tables()

Baoquan He
2017-08-04T12:30:45Z

On 08/04/17 at 02:09pm, Joerg Roedel wrote:
>
> On Tue, Aug 01, 2017 at 07:37:21PM +0800, Baoquan He wrote:
> > + for_each_iommu(iommu) {

......

> > + if (copied)
> > + continue;
> > +
> > + old_devtb_phys = entry & PAGE_MASK;
> > + old_devtb = memremap(old_devtb_phys, dev_table_size, MEMREMAP_WB);
> > + if (!old_devtb)
> > + return -1;
>
> You forgot to check whether the old device table is also below 4GB.
>
> > +
> > + gfp_flag = GFP_KERNEL | __GFP_ZERO;
> > + old_dev_tbl_cpy = (void *)__get_free_pages(gfp_flag,
> > + get_order(dev_table_size));
> > + if (old_dev_tbl_cpy == NULL) {
> > + pr_err("Failed to allocate memory for copying old device table!/n");
> > + return -1;
> > + }
> > +
> > + for (devid = 0; devid <= amd_iommu_last_bdf; ++devid) {
> > + old_dev_tbl_cpy[devid] = old_devtb[devid];
> > + dom_id = old_devtb[devid].data[1] & DEV_DOMID_MASK;
> > + dte_v = old_devtb[devid].data[0] & DTE_FLAG_V;
> > + if (dte_v && dom_id)
> > + __set_bit(dom_id, amd_iommu_pd_alloc_bitmap);
> > + }
> > + memunmap(old_devtb);
> > + copied = 1;
>
> And this one should be outside of the loop, then you can get rid of the
> 'copied' variable. Also I don't really understand why you need a
> temporary copy of the old device-table. Can't you just smart-copy the
> contents of the old table to the real new one?

Sorry, I don't get 'this one' meaning, are you suggesting the copy for
loop should be take out of the iommu for loop?

About the temporary copy of the old device-table, you can see in patch
7/13, if irq sanity check failed, it return -1. This return could happen
in the middle of copy. So I think we should do a whole successful copy,
or don't copy at all. It might not be good do half copy.