From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH V1 1/1] iommu: Make sure device's ID array elements are unique To: Alex Williamson , Tomasz Nowicki Cc: joro@8bytes.org, robin.murphy@arm.com, will.deacon@arm.com, lorenzo.pieralisi@arm.com, bhelgaas@google.com, Jayachandran.Nair@cavium.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-acpi@vger.kernel.org, iommu@lists.linux-foundation.org, Ganapatrao.Kulkarni@cavium.com, mw@semihalf.com, linux-arm-kernel@lists.infradead.org References: <1513696436-31834-1-git-send-email-tomasz.nowicki@caviumnetworks.com> <1513696821-32291-1-git-send-email-tomasz.nowicki@caviumnetworks.com> <20171219093726.432e16e7@t450s.home> From: Tomasz Nowicki Message-ID: <668cc552-e37d-bdff-4d8e-e81516fb0ca0@semihalf.com> Date: Wed, 20 Dec 2017 11:28:29 +0100 MIME-Version: 1.0 In-Reply-To: <20171219093726.432e16e7@t450s.home> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-acpi-owner@vger.kernel.org List-ID: On 19.12.2017 17:37, Alex Williamson wrote: > On Tue, 19 Dec 2017 16:20:21 +0100 > Tomasz Nowicki wrote: > >> While iterating over DMA aliases for a PCI device, for some rare cases >> (i.e. PCIe-to-PCI/X bridges) we may get exactly the same ID as initial child >> device. In turn, the same ID may get registered for a device multiple times. >> Eventually IOMMU driver may try to configure the same ID within domain >> multiple times too which for some IOMMU drivers is illegal and causes kernel >> panic. >> >> Rule out ID duplication prior to device ID array registration. >> >> CC: stable@vger.kernel.org # v4.14+ > > You've identified a release, is there a specific commit this fixes? Yes, it was triggered by converting drm_pci_init() to pci_register_driver() in ast_drv.c Fixes: 10631d724def ("drm/pci: Deprecate drm_pci_init/exit completely ") > >> Signed-off-by: Tomasz Nowicki >> --- >> drivers/iommu/iommu.c | 28 ++++++++++++++++++++++++++++ >> 1 file changed, 28 insertions(+) >> >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index 3de5c0b..9b2c138 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -1945,6 +1945,31 @@ void iommu_fwspec_free(struct device *dev) >> } >> EXPORT_SYMBOL_GPL(iommu_fwspec_free); >> >> +static void iommu_fwspec_remove_ids_dup(struct device *dev, u32 *ids, >> + int *num_ids) >> +{ >> + struct iommu_fwspec *fwspec = dev->iommu_fwspec; >> + int i, j, k, valid_ids = *num_ids; >> + >> + for (i = 0; i < valid_ids; i++) { >> + for (j = 0; j < fwspec->num_ids; j++) { >> + if (ids[i] != fwspec->ids[j]) >> + continue; >> + >> + dev_info(dev, "found 0x%x ID duplication, skipped\n", >> + ids[i]); >> + >> + for (k = i + 1; k < valid_ids; k++) >> + ids[k - 1] = ids[k]; > > Use memmove()? Right. > >> + >> + valid_ids--; >> + break; > > At this point ids[i] is not the ids[i] that we tested for dupes, it's > what was ids[i + 1], but we're going to i++ on the next iteration and > we therefore never test that entry. Good point. Now the fundamental question is where we should put the patch, here or in SMMUv3 driver as per Robin suggestion. Thanks, Tomasz