From: Joe Jin <email@example.com> To: Paul Durrant <Paul.Durrant@citrix.com>, Boris Ostrovsky <firstname.lastname@example.org>, Konrad Rzeszutek Wilk <email@example.com> Cc: John Sobecki <firstname.lastname@example.org>, "DONGLI.ZHANG" <email@example.com>, "firstname.lastname@example.org\"" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, Christoph Helwig <firstname.lastname@example.org> Subject: Re: [Xen-devel] [PATCH] xen-swiotlb: exchange memory with Xen only when pages are contiguous Date: Tue, 30 Oct 2018 07:48:07 -0700 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <097f1f6f16f7415aa3a52a7c4f5e52dc@AMSPEX02CL03.citrite.net> On 10/30/18 7:21 AM, Paul Durrant wrote: >> -----Original Message----- >> From: Xen-devel [mailto:firstname.lastname@example.org] On Behalf >> Of Joe Jin >> Sent: 30 October 2018 14:13 >> To: Paul Durrant <Paul.Durrant@citrix.com>; Boris Ostrovsky >> <email@example.com>; Konrad Rzeszutek Wilk >> <firstname.lastname@example.org> >> Cc: John Sobecki <email@example.com>; DONGLI.ZHANG >> <firstname.lastname@example.org>; email@example.com" <linux- >> firstname.lastname@example.org>; email@example.com; xen- >> firstname.lastname@example.org; Christoph Helwig <email@example.com> >> 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 >
next prev parent reply other threads:[~2018-10-30 14:48 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-10-24 3:09 Joe Jin 2018-10-24 13:02 ` Konrad Rzeszutek Wilk 2018-10-24 13:57 ` Boris Ostrovsky 2018-10-24 14:43 ` Joe Jin 2018-10-25 11:45 ` Boris Ostrovsky 2018-10-25 14:23 ` Joe Jin 2018-10-25 16:10 ` Boris Ostrovsky 2018-10-25 16:28 ` Joe Jin 2018-10-25 18:56 ` Joe Jin 2018-10-26 7:48 ` Christoph Helwig 2018-10-26 8:54 ` Dongli Zhang 2018-10-26 14:48 ` Joe Jin 2018-10-26 14:40 ` Joe Jin 2018-10-30 2:51 ` Joe Jin [not found] ` <57e5593233c64dc0a36c7d4c750a1ed4@AMSPEX02CL03.citrite.net> 2018-10-30 14:12 ` [Xen-devel] " Joe Jin [not found] ` <097f1f6f16f7415aa3a52a7c4f5e52dc@AMSPEX02CL03.citrite.net> 2018-10-30 14:48 ` Joe Jin [this message] 2018-10-24 16:05 ` Joe Jin
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