From 2079f6582c6d6452aaa7556812ba791bc57e350f Mon Sep 17 00:00:00 2001 From: Laura Abbott Date: Mon, 20 May 2019 22:21:02 -0400 Subject: [PATCH] iommu/arm-smmu: workaround DMA mode issues Message-id: <20190520222102.19488-1-labbott@redhat.com> Patchwork-id: 259215 O-Subject: [ARK INTERNAL PATCH] iommu/arm-smmu: workaround DMA mode issues Bugzilla: RH-Acked-by: Mark Langsdorf RH-Acked-by: Mark Salter From: Mark Salter Rebased for v5.2-rc1 Bugzilla: 1652259 Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=19244562 Upstream status: RHEL only. rhel8 commit 65feb1ed0ec9a088a63a90d46c0f7563ac96ad0f Author: Mark Salter Date: Wed Nov 21 17:15:59 2018 +0100 [iommu] iommu/arm-smmu: workaround DMA mode issues Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1624077 Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=18112820 Testing: Verified iommu.passthrough=1 no longer needed on gigabyte platforms. Upstream Status: RHEL-only In RHEL_ALT 7.5 we carried a RHEL-only patch which forced the arm smmuv2 into bypass mode due to performance issues on CN88xx. This was intended to be a temporary hack until the issues were resolved. Another vendor had issues with the iommu in bypass mode so we reverted the RHEL-only patch so that iommu is in DMA mode by default (upstream default). It turns on that there are remaining SMMU DMA mode issues on Gigabyte platformws with CN88xx cpus. The problem manifests itself by pcie card drivers failing to initialize the cards when SMMU is in DMA mode. The root cause has not been determined yet, but looks likely to be a hw or firmware issue. This patch forces bypass mode for Gigabyte platforms. CN88xx isn't officially supported in RHEL but we have a lot of them being used internally for testing, so I think we want this to support that use case in RHEL8. Signed-off-by: Mark Salter Signed-off-by: Herton R. Krzesinski Acked-by: Mark Salter Acked-by: Donald Dutile Upstream Status: RHEL only Signed-off-by: Laura Abbott --- drivers/iommu/iommu.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 2b471419e26c..83c8d9845aed 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -7,6 +7,7 @@ #define pr_fmt(fmt) "iommu: " fmt #include +#include #include #include #include @@ -2658,3 +2659,24 @@ int iommu_sva_get_pasid(struct iommu_sva *handle) return ops->sva_get_pasid(handle); } EXPORT_SYMBOL_GPL(iommu_sva_get_pasid); + +#ifdef CONFIG_ARM64 +static int __init iommu_quirks(void) +{ + const char *vendor, *name; + + vendor = dmi_get_system_info(DMI_SYS_VENDOR); + name = dmi_get_system_info(DMI_PRODUCT_NAME); + + if (vendor && + (strncmp(vendor, "GIGABYTE", 8) == 0 && name && + (strncmp(name, "R120", 4) == 0 || + strncmp(name, "R270", 4) == 0))) { + pr_warn("Gigabyte %s detected, force iommu passthrough mode", name); + iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY; + } + + return 0; +} +arch_initcall(iommu_quirks); +#endif -- 2.26.2