queue-4.19/iommu-arm-smmu-v3-don-t-disable-smmu-in-kdump-kernel.patch

   1 From abaa80c71ba926dfc788a37cfad7db31121304ac Mon Sep 17 00:00:00 2001
   2 From: Will Deacon <will.deacon@arm.com>
   3 Date: Tue, 23 Apr 2019 11:59:36 +0100
   4 Subject: iommu/arm-smmu-v3: Don't disable SMMU in kdump kernel
   5
   6 [ Upstream commit 3f54c447df34ff9efac7809a4a80fd3208efc619 ]
   7
   8 Disabling the SMMU when probing from within a kdump kernel so that all
   9 incoming transactions are terminated can prevent the core of the crashed
  10 kernel from being transferred off the machine if all I/O devices are
  11 behind the SMMU.
  12
  13 Instead, continue to probe the SMMU after it is disabled so that we can
  14 reinitialise it entirely and re-attach the DMA masters as they are reset.
  15 Since the kdump kernel may not have drivers for all of the active DMA
  16 masters, we suppress fault reporting to avoid spamming the console and
  17 swamping the IRQ threads.
  18
  19 Reported-by: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
  20 Tested-by: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
  21 Tested-by: Bhupesh Sharma <bhsharma@redhat.com>
  22 Signed-off-by: Will Deacon <will.deacon@arm.com>
  23 Signed-off-by: Sasha Levin <sashal@kernel.org>
  24 ---
  25  drivers/iommu/arm-smmu-v3.c | 10 ++++------
  26  1 file changed, 4 insertions(+), 6 deletions(-)
  27
  28 diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
  29 index 9ae3678844eb..40fbf20d69e5 100644
  30 --- a/drivers/iommu/arm-smmu-v3.c
  31 +++ b/drivers/iommu/arm-smmu-v3.c
  32 @@ -2414,13 +2414,9 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
  33         /* Clear CR0 and sync (disables SMMU and queue processing) */
  34         reg = readl_relaxed(smmu->base + ARM_SMMU_CR0);
  35         if (reg & CR0_SMMUEN) {
  36 -               if (is_kdump_kernel()) {
  37 -                       arm_smmu_update_gbpa(smmu, GBPA_ABORT, 0);
  38 -                       arm_smmu_device_disable(smmu);
  39 -                       return -EBUSY;
  40 -               }
  41 -
  42                 dev_warn(smmu->dev, "SMMU currently enabled! Resetting...\n");
  43 +               WARN_ON(is_kdump_kernel() && !disable_bypass);
  44 +               arm_smmu_update_gbpa(smmu, GBPA_ABORT, 0);
  45         }
  46
  47         ret = arm_smmu_device_disable(smmu);
  48 @@ -2513,6 +2509,8 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
  49                 return ret;
  50         }
  51
  52 +       if (is_kdump_kernel())
  53 +               enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
  54
  55         /* Enable the SMMU interface, or ensure bypass */
  56         if (!bypass || disable_bypass) {
  57 --
  58 2.20.1
  59