On 10/30/18 7:21 AM, Paul Durrant wrote: >> -----Original Message----- >> From: Xen-devel [mailto:xen-devel-boun...@lists.xenproject.org] On Behalf >> Of Joe Jin >> Sent: 30 October 2018 14:13 >> To: Paul Durrant <paul.durr...@citrix.com>; Boris Ostrovsky >> <boris.ostrov...@oracle.com>; Konrad Rzeszutek Wilk >> <konrad.w...@oracle.com> >> Cc: John Sobecki <john.sobe...@oracle.com>; DONGLI.ZHANG >> <dongli.zh...@oracle.com>; linux-ker...@vger.kernel.org" <linux- >> ker...@vger.kernel.org>; kon...@kernel.org; xen- >> de...@lists.xenproject.org; Christoph Helwig <h...@lst.de> >> Subject: Re: [Xen-devel] [PATCH] xen-swiotlb: exchange memory with Xen >> only when pages are contiguous >> >> On 10/30/18 1:59 AM, Paul Durrant wrote: >>>> On 10/25/18 11:56 AM, Joe Jin wrote: >>>>> I just discussed this patch with Boris in private, his opinions(Boris, >>>>> please correct me if any misunderstood) are: >>>>> >>>>> 1. With/without the check, both are incorrect, he thought we need to >>>>> prevented unalloc'd free at here. >>>>> 2. On freeing, if upper layer already checked the memory was DMA-able, >>>>> the checking at here does not make sense, we can remove all checks. >>>>> 3. xen_create_contiguous_region() and xen_destroy_contiguous_region() >>>>> to come in pairs. >>>> I tried to added radix_tree to track allocating/freeing and I found >> some >>>> memory only allocated but was not freed, I guess it caused by driver >> used >>>> dma_pool, that means if lots of such requests, the list will consume >> lot >>>> of memory for it. Will continue to work on it, if anyone have good idea >>>> for it please let me know, I'd like to try it. >>>> >>> FWIW, in my Xen PV-IOMMU test patches, I have also tried keeping a list >> of ranges mapped for DMA and have discovered apparent issues with some >> drivers, particularly tg3, that seem to free mappings that have not been >> allocated (or possibly double-free). I've never fully tracked down the >> issue. >> >> Call trace of first called xen_swiotlb_alloc_coherent(The pages never >> backed to Xen): >> >> [ 23.436333] [<ffffffff814040c9>] >> xen_swiotlb_alloc_coherent+0x169/0x510 >> [ 23.436623] [<ffffffff811eb38d>] ? kmem_cache_alloc_trace+0x1ed/0x280 >> [ 23.436900] [<ffffffff811d72af>] dma_pool_alloc+0x11f/0x260 >> [ 23.437190] [<ffffffff81537442>] ehci_qh_alloc+0x52/0x120 >> [ 23.437481] [<ffffffff8153b80f>] ehci_setup+0x2bf/0x8e0 >> [ 23.437760] [<ffffffff81476d06>] ? __dev_printk+0x46/0xa0 >> [ 23.438042] [<ffffffff814770b3>] ? _dev_info+0x53/0x60 >> [ 23.438327] [<ffffffff8153f620>] ehci_pci_setup+0xc0/0x5f0 >> [ 23.438615] [<ffffffff81519fcd>] usb_add_hcd+0x25d/0xaf0 >> [ 23.438901] [<ffffffff8152c9a6>] usb_hcd_pci_probe+0x406/0x520 >> [ 23.439177] [<ffffffff8153f486>] ehci_pci_probe+0x36/0x40 >> [ 23.439469] [<ffffffff8136e99a>] local_pci_probe+0x4a/0xb0 >> [ 23.439752] [<ffffffff8136fba5>] ? pci_match_device+0xe5/0x110 >> [ 23.440027] [<ffffffff8136fce1>] pci_device_probe+0xd1/0x120 >> [ 23.440320] [<ffffffff8147b13c>] driver_probe_device+0x20c/0x4d0 >> [ 23.440599] [<ffffffff8147b4eb>] __driver_attach+0x9b/0xa0 >> [ 23.440879] [<ffffffff8147b450>] ? __device_attach+0x50/0x50 >> >> Above was EHCI used DMA pool to allocate DMA memory. >> >> During my testing, ~1000 entries was not freed, if more PCI devices >> use DMA pool, the tree/list will have more entries, looks it's not a >> good idea that use a list to track it. >> > > Yes, it seems pools can hang onto a serious number of allocations so a list > is probably not wise.
I agree with you. > What I was pointing out, though, is that it appears you can't even track > mappings (as opposed to allocations) with a list. Right. > either because drivers apparently try to unmap things they have not mapped. If this happened, should be fixed by driver :) Thanks, Joe > > Paul > _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
