Hi Sammer, On 11/04/18 16:58, Goel, Sameer wrote: > > > On 3/28/2018 9:00 AM, Marc Zyngier wrote: >> On 2018-03-28 15:39, Timur Tabi wrote: >>> From: Sameer Goel <[email protected]> >>> >>> Set SMMU_GBPA to abort all incoming translations during the SMMU reset >>> when SMMUEN==0. >>> >>> This prevents a race condition where a stray DMA from the crashed primary >>> kernel can try to access an IOVA address as an invalid PA when SMMU is >>> disabled during reset in the crash kernel. >>> >>> Signed-off-by: Sameer Goel <[email protected]> >>> --- >>> drivers/iommu/arm-smmu-v3.c | 12 ++++++++++++ >>> 1 file changed, 12 insertions(+) >>> >>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c >>> index 3f2f1fc68b52..c04a89310c59 100644 >>> --- a/drivers/iommu/arm-smmu-v3.c >>> +++ b/drivers/iommu/arm-smmu-v3.c >>> @@ -2458,6 +2458,18 @@ static int arm_smmu_device_reset(struct >>> arm_smmu_device *smmu, bool bypass) >>> if (reg & CR0_SMMUEN) >>> dev_warn(smmu->dev, "SMMU currently enabled! Resetting...\n"); >>> >>> + /* >>> + * Abort all incoming translations. This can happen in a kdump case >>> + * where SMMU is initialized when a prior DMA is pending. Just >>> + * disabling the SMMU in this case might result in writes to invalid >>> + * PAs. >>> + */ >>> + ret = arm_smmu_update_gbpa(smmu, 1, GBPA_ABORT); >>> + if (ret) { >>> + dev_err(smmu->dev, "GBPA not responding to update\n"); >>> + return ret; >>> + } >>> + >>> ret = arm_smmu_device_disable(smmu); >>> if (ret) >>> return ret; >> >> A tangential question: can we reliably detect that the SMMU already >> has valid mappings, which would indicate that we're in a pretty bad >> shape already by the time we set that bit? For all we know, memory >> could have been corrupted long before we hit this point, and this >> patch barely narrows the window of opportunity. > > :) Yes that is correct. This only covers the kdump scenario. Trying > to get some reliability when booting up the crash kernel. The system > is already in a bad state. I don't think that this will happen in a > normal scenario. But please point me to the GICv3 change and I'll > have a look.
See this: https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/tree/drivers/irqchip/irq-gic-v3-its.c?h=irq/irqchip-4.17&id=6eb486b66a3094cdcd68dc39c9df3a29d6a51dd5#n3407 M. -- Jazz is not dead. It just smells funny... _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
