4.18-stable review patch. If anyone has any objections, please let me know.
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From: Will Deacon will.deacon@arm.com
[ Upstream commit b63b3439b85609338e4faabd5d2588dbda137e5c ]
If we find that the SMMU is enabled during probe, we reset it by re-initialising its registers and either enabling translation or placing it into bypass based on the disable_bypass commandline option.
In the case of a kdump kernel, the SMMU won't have been shutdown cleanly by the previous kernel and there may be concurrent DMA through the SMMU. Rather than reset the SMMU to bypass, which would likely lead to rampant data corruption, we can instead configure the SMMU to abort all incoming transactions when we find that it is enabled from within a kdump kernel.
Reported-by: Sameer Goel sgoel@codeaurora.org Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iommu/arm-smmu-v3.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)
--- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -24,6 +24,7 @@ #include <linux/acpi_iort.h> #include <linux/bitfield.h> #include <linux/bitops.h> +#include <linux/crash_dump.h> #include <linux/delay.h> #include <linux/dma-iommu.h> #include <linux/err.h> @@ -2211,8 +2212,12 @@ static int arm_smmu_update_gbpa(struct a reg &= ~clr; reg |= set; writel_relaxed(reg | GBPA_UPDATE, gbpa); - return readl_relaxed_poll_timeout(gbpa, reg, !(reg & GBPA_UPDATE), - 1, ARM_SMMU_POLL_TIMEOUT_US); + ret = readl_relaxed_poll_timeout(gbpa, reg, !(reg & GBPA_UPDATE), + 1, ARM_SMMU_POLL_TIMEOUT_US); + + if (ret) + dev_err(smmu->dev, "GBPA not responding to update\n"); + return ret; }
static void arm_smmu_free_msis(void *data) @@ -2392,8 +2397,15 @@ static int arm_smmu_device_reset(struct
/* Clear CR0 and sync (disables SMMU and queue processing) */ reg = readl_relaxed(smmu->base + ARM_SMMU_CR0); - if (reg & CR0_SMMUEN) + if (reg & CR0_SMMUEN) { + if (is_kdump_kernel()) { + arm_smmu_update_gbpa(smmu, GBPA_ABORT, 0); + arm_smmu_device_disable(smmu); + return -EBUSY; + } + dev_warn(smmu->dev, "SMMU currently enabled! Resetting...\n"); + }
ret = arm_smmu_device_disable(smmu); if (ret) @@ -2491,10 +2503,8 @@ static int arm_smmu_device_reset(struct enables |= CR0_SMMUEN; } else { ret = arm_smmu_update_gbpa(smmu, 0, GBPA_ABORT); - if (ret) { - dev_err(smmu->dev, "GBPA not responding to update\n"); + if (ret) return ret; - } } ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0, ARM_SMMU_CR0ACK);