From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yijing Wang Subject: Re: [PATCH] iommu/vt-d: Fix broken device issue when using iommu=pt Date: Mon, 11 Aug 2014 16:36:48 +0800 Message-ID: <53E880A0.3040702@huawei.com> References: <1407725674-27271-1-git-send-email-wangyijing@huawei.com> <1407732187.9800.11.camel@ul30vt.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1407732187.9800.11.camel-85EaTFmN5p//9pzu0YdTqQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Alex Williamson Cc: David Woodhouse , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Jiang Liu List-Id: iommu@lists.linux-foundation.org >> extern struct iommu_table_entry __iommu_table[], __iommu_table_end[]; >> >> @@ -146,6 +148,7 @@ void dma_generic_free_coherent(struct device *dev, size_t size, void *vaddr, >> */ >> static __init int iommu_setup(char *p) >> { >> + char *end; >> iommu_merge = 1; >> >> if (!p) >> @@ -192,6 +195,11 @@ static __init int iommu_setup(char *p) >> #endif >> if (!strncmp(p, "pt", 2)) >> iommu_pass_through = 1; >> + if (!strncmp(p, "pt_force=", 9)) { >> + iommu_pass_through = 1; >> + iommu_pt_force_domain = simple_strtol(p+9, &end, 0); >> + iommu_pt_force_bus = simple_strtol(end+1, NULL, 0); > > Documentation/kernel-parameters.txt? Oh, I missed it, I will update it if other guys think the patch is the right fix to the issue later. > >> + } >> >> gart_parse_options(p); >> >> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c >> index d1f5caa..49757f1 100644 >> --- a/drivers/iommu/intel-iommu.c >> +++ b/drivers/iommu/intel-iommu.c >> @@ -2705,6 +2705,47 @@ static int __init iommu_prepare_static_identity_mapping(int hw) >> return ret; >> } >> >> + /* We found some strange devices in HP c7000 and other platforms that >> + * can not be enumerated by OS, but they did DMA read/write without >> + * driver management, so we should create the pt mapping for these >> + * devices to avoid DMA errors. Add iommu=pt_force=segment:busnum to >> + * force to do pt context mapping in the bus number. >> + */ > > So best case with this patch is that the user needs to discover that > this option exists, figure out the undocumented parameters, be running > on VT-d, permanently add a kernel commandline option, and never have any > intention of assigning the device to userspace or a VM... Hmmm, we can add some detection code in dmar fault process functions, and print some useful messages. > > Can't we handle this with the DMA alias quirks that are now in 3.17? Or > can the vendor fix this with a firmware update? This device behavior is > really quite broken for this kind of server class product. Thanks, Currently, I don't know how many devices have this issue. So I'm not sure the vendor fix is a proper way to fix it. Alex, sorry, I don't understand the firmware update to fix it? Do you mean updating the device EEPROM firmware ? Thanks! Yijing. > > Alex > >> + if (iommu_pt_force_bus >= 0 && iommu_pt_force_bus >= 0) { >> + int found = 0; >> + >> + iommu = NULL; >> + for_each_active_iommu(iommu, drhd) { >> + if (iommu_pt_force_domain != drhd->segment) >> + continue; >> + >> + for_each_active_dev_scope(drhd->devices, drhd->devices_cnt, i, dev) { >> + if (!dev_is_pci(dev)) >> + continue; >> + >> + pdev = to_pci_dev(dev); >> + if (pdev->bus->number == iommu_pt_force_bus || >> + (pdev->subordinate >> + && pdev->subordinate->number <= iommu_pt_force_bus >> + && pdev->subordinate->busn_res.end >= iommu_pt_force_bus)) { >> + found = 1; >> + break; >> + } >> + } >> + >> + if (drhd->include_all) { >> + found = 1; >> + break; >> + } >> + } >> + >> + if (found && iommu) >> + for (i = 0; i < 256; i++) >> + domain_context_mapping_one(si_domain, iommu, iommu_pt_force_bus, >> + i, hw ? CONTEXT_TT_PASS_THROUGH : >> + CONTEXT_TT_MULTI_LEVEL); >> + } >> + >> return 0; >> } >> > > > > > . > -- Thanks! Yijing