From 1817b2ccbd11cbbe64a3d38972ef924d9334d912 Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Wed, 17 Oct 2018 21:32:58 +0100 Subject: [PATCH] iommu/arm-smmu-v3: Fix big-endian CMD_SYNC writes commit 3cd508a8c1379427afb5e16c2e0a7c986d907853 upstream. When we insert the sync sequence number into the CMD_SYNC.MSIData field, we do so in CPU-native byte order, before writing out the whole command as explicitly little-endian dwords. Thus on big-endian systems, the SMMU will receive and write back a byteswapped version of sync_nr, which would be perfect if it were targeting a similarly-little-endian ITS, but since it's actually writing back to memory being polled by the CPUs, they're going to end up seeing the wrong thing. Since the SMMU doesn't care what the MSIData actually contains, the minimal-overhead solution is to simply add an extra byteswap initially, such that it then writes back the big-endian format directly. Cc: Fixes: 37de98f8f1cf ("iommu/arm-smmu-v3: Use CMD_SYNC completion MSI") Signed-off-by: Robin Murphy Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- drivers/iommu/arm-smmu-v3.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 5059d09..3e02aac 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -837,7 +837,13 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV); cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH); cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB); - cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent->sync.msidata); + /* + * Commands are written little-endian, but we want the SMMU to + * receive MSIData, and thus write it back to memory, in CPU + * byte order, so big-endian needs an extra byteswap here. + */ + cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, + cpu_to_le32(ent->sync.msidata)); cmd[1] |= ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; break; default: -- 2.7.4