From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org, x86@kernel.org,
Anshuman Khandual <anshuman.khandual@arm.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Juergen Gross <jgross@suse.com>, Joerg Roedel <joro@8bytes.org>,
David Woodhouse <dwmw2@infradead.org>,
Lu Baolu <baolu.lu@linux.intel.com>,
Robin Murphy <robin.murphy@arm.com>,
linux-arm-kernel@lists.infradead.org,
xen-devel@lists.xenproject.org, linux-ia64@vger.kernel.org,
linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
linux-hyperv@vger.kernel.org, tboot-devel@lists.sourceforge.net,
linux-pci@vger.kernel.org
Subject: Re: [PATCH 12/15] swiotlb: provide swiotlb_init variants that remap the buffer
Date: Tue, 15 Mar 2022 20:39:29 -0400 [thread overview]
Message-ID: <3a8cc553-4b60-b6bb-a2d8-2b33c4c1cf23@oracle.com> (raw)
In-Reply-To: <20220315063618.GA1244@lst.de>
On 3/15/22 2:36 AM, Christoph Hellwig wrote:
> @@ -271,12 +273,23 @@ void __init swiotlb_init(bool addressing_limit, unsigned int flags)
> * allow to pick a location everywhere for hypervisors with guest
> * memory encryption.
> */
> +retry:
> + bytes = PAGE_ALIGN(default_nslabs << IO_TLB_SHIFT);
> if (flags & SWIOTLB_ANY)
> tlb = memblock_alloc(bytes, PAGE_SIZE);
> else
> tlb = memblock_alloc_low(bytes, PAGE_SIZE);
> if (!tlb)
> goto fail;
> + if (remap && remap(tlb, nslabs) < 0) {
> + memblock_free(tlb, PAGE_ALIGN(bytes));
> +
> + if (nslabs <= IO_TLB_MIN_SLABS)
> + panic("%s: Failed to remap %zu bytes\n",
> + __func__, bytes);
> + nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
I spoke with Konrad (who wrote the original patch --- f4b2f07b2ed9b469ead87e06fc2fc3d12663a725) and apparently the reason for 2MB was to optimize for Xen's slab allocator, it had nothing to do with IO_TLB_MIN_SLABS. Since this is now common code we should not expose Xen-specific optimizations here and smaller values will still work so IO_TLB_MIN_SLABS is fine.
I think this should be mentioned in the commit message though, probably best in the next patch where you switch to this code.
As far as the hunk above, I don't think we need the max() here: with IO_TLB_MIN_SLABS being 512 we may get stuck in an infinite loop. Something like
nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
if (nslabs <= IO_TLB_MIN_SLABS)
panic()
should be sufficient.
> + goto retry;
> + }
> if (swiotlb_init_with_tbl(tlb, default_nslabs, flags))
> goto fail_free_mem;
> return;
> @@ -287,12 +300,18 @@ void __init swiotlb_init(bool addressing_limit, unsigned int flags)
> pr_warn("Cannot allocate buffer");
> }
>
> +void __init swiotlb_init(bool addressing_limit, unsigned int flags)
> +{
> + return swiotlb_init_remap(addressing_limit, flags, NULL);
> +}
> +
> /*
> * Systems with larger DMA zones (those that don't support ISA) can
> * initialize the swiotlb later using the slab allocator if needed.
> * This should be just like above, but with some error catching.
> */
> -int swiotlb_init_late(size_t size, gfp_t gfp_mask)
> +int swiotlb_init_late(size_t size, gfp_t gfp_mask,
> + int (*remap)(void *tlb, unsigned long nslabs))
> {
> unsigned long nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
> unsigned long bytes;
> @@ -303,6 +322,7 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask)
> if (swiotlb_force_disable)
> return 0;
>
> +retry:
> order = get_order(nslabs << IO_TLB_SHIFT);
> nslabs = SLABS_PER_PAGE << order;
> bytes = nslabs << IO_TLB_SHIFT;
> @@ -317,6 +337,16 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask)
>
> if (!vstart)
> return -ENOMEM;
> + if (remap)
> + rc = remap(vstart, nslabs);
> + if (rc) {
> + free_pages((unsigned long)vstart, order);
> +
> + if (IO_TLB_MIN_SLABS <= 1024)
> + return rc;
> + nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
Same here. (The 'if' check above is wrong anyway).
Patches 13 and 14 look good.
-boris
> + goto retry;
> + }
>
> if (order != get_order(bytes)) {
> pr_warn("only able to allocate %ld MB\n",
next prev parent reply other threads:[~2022-03-16 0:41 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-14 7:31 cleanup swiotlb initialization v5 Christoph Hellwig
2022-03-14 7:31 ` [PATCH 01/15] dma-direct: use is_swiotlb_active in dma_direct_map_page Christoph Hellwig
2022-03-14 7:31 ` [PATCH 02/15] swiotlb: make swiotlb_exit a no-op if SWIOTLB_FORCE is set Christoph Hellwig
2022-03-14 7:31 ` [PATCH 03/15] swiotlb: simplify swiotlb_max_segment Christoph Hellwig
2022-03-14 7:31 ` [PATCH 04/15] swiotlb: rename swiotlb_late_init_with_default_size Christoph Hellwig
2022-03-14 7:31 ` [PATCH 05/15] arm/xen: don't check for xen_initial_domain() in xen_create_contiguous_region Christoph Hellwig
2022-03-14 7:31 ` [PATCH 06/15] MIPS/octeon: use swiotlb_init instead of open coding it Christoph Hellwig
2022-03-14 7:31 ` [PATCH 07/15] x86: remove the IOMMU table infrastructure Christoph Hellwig
2022-03-14 7:31 ` [PATCH 08/15] x86: centralize setting SWIOTLB_FORCE when guest memory encryption is enabled Christoph Hellwig
2022-03-14 7:31 ` [PATCH 09/15] swiotlb: make the swiotlb_init interface more useful Christoph Hellwig
2022-03-14 7:31 ` [PATCH 10/15] swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction Christoph Hellwig
2022-03-14 7:31 ` [PATCH 11/15] swiotlb: pass a gfp_mask argument to swiotlb_init_late Christoph Hellwig
2022-03-14 7:31 ` [PATCH 12/15] swiotlb: provide swiotlb_init variants that remap the buffer Christoph Hellwig
2022-03-14 22:39 ` Boris Ostrovsky
2022-03-15 6:36 ` Christoph Hellwig
2022-03-16 0:39 ` Boris Ostrovsky [this message]
2022-03-14 7:31 ` [PATCH 13/15] swiotlb: merge swiotlb-xen initialization into swiotlb Christoph Hellwig
2022-03-14 23:07 ` Boris Ostrovsky
2022-03-15 6:48 ` Christoph Hellwig
2022-03-15 0:00 ` Stefano Stabellini
2022-03-14 7:31 ` [PATCH 14/15] swiotlb: remove swiotlb_init_with_tbl and swiotlb_init_late_with_tbl Christoph Hellwig
2022-03-14 23:11 ` Boris Ostrovsky
2022-03-14 7:31 ` [PATCH 15/15] x86: remove cruft from <asm/dma-mapping.h> Christoph Hellwig
2022-04-04 5:05 cleanup swiotlb initialization v8 Christoph Hellwig
2022-04-04 5:05 ` [PATCH 12/15] swiotlb: provide swiotlb_init variants that remap the buffer Christoph Hellwig
2022-04-04 7:09 ` Dongli Zhang
[not found] ` <67c1784af6f24f3e871ddfb1478e821c@FR3P281MB0843.DEUP281.PROD.OUTLOOK.COM>
2022-04-04 6:19 ` Alan Robinson
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