linux-kernel - Re: [PATCH v9 05/13] iommu/amd: Add function copy_dev

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Date:   Fri, 4 Aug 2017 14:09:08 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Baoquan He <bhe@...hat.com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 05/13] iommu/amd: Add function copy_dev_tables()

Hi Baoquan,

On Tue, Aug 01, 2017 at 07:37:21PM +0800, Baoquan He wrote:
> +	for_each_iommu(iommu) {
> +		/* All IOMMUs should use the same device table with the same size */
> +		lo = readl(iommu->mmio_base + MMIO_DEV_TABLE_OFFSET);
> +		hi = readl(iommu->mmio_base + MMIO_DEV_TABLE_OFFSET + 4);
> +		entry = (((u64) hi) << 32) + lo;
> +		if (last_entry && last_entry != entry) {
> +			pr_err("IOMMU:%d should use the same dev table as others!/n",
> +				iommu->index);
> +			return -1;
> +		}
> +		last_entry = entry;
> +
> +		old_devtb_size = ((entry & ~PAGE_MASK) + 1) << 12;
> +		if (old_devtb_size != dev_table_size) {
> +			pr_err("The device table size of IOMMU:%d is not expected!/n",
> +				iommu->index);
> +			return -1;
> +		}
> +
> +		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?


Regards,

	Joerg