[Xen-changelog] [xen staging] arm,

[p***@xen.org]

commit ce75973a273f6cacce2b2b8ace1d3ab4b304c361
Author: Stefano Stabellini <***@xilinx.com>
AuthorDate: Sun Oct 14 15:57:32 2018 -0700
Commit: Stefano Stabellini <***@kernel.org>
CommitDate: Mon Oct 29 14:24:28 2018 -0700

arm,smmu: backport "Disable stalling faults for all endpoints"

Backport commit 3714ce1d6655098ee69ede632883e5874d67e4ab
"iommu/arm-smmu: Disable stalling faults for all endpoints" from the
Linux kernel. This works-around Erratum #842869.

Original commit message:

Enabling stalling faults can result in hardware deadlock on poorly
designed systems, particularly those with a PCI root complex upstream of
the SMMU.

Although it's not really Linux's job to save hardware integrators from
their own misfortune, it *is* our job to stop userspace (e.g. VFIO
clients) from hosing the system for everybody else, even if they might
already be required to have elevated privileges.

Given that the fault handling code currently executes entirely in IRQ
context, there is nothing that can sensibly be done to recover from
things like page faults anyway, so let's rip this code out for now and
avoid the potential for deadlock.

Cc: <***@vger.kernel.org>
Fixes: 48ec83bcbcf5 ("iommu/arm-smmu: Add initial driver support for ARM SMMUv3 devices")
Reported-by: Matt Evans <***@arm.com>
Signed-off-by: Will Deacon <***@arm.com>

Signed-off-by: Stefano Stabellini <***@xilinx.com>
Acked-by: Julien Grall <***@arm.com>
---
docs/misc/arm/silicon-errata.txt | 1 +
xen/drivers/passthrough/arm/smmu.c | 40 ++++++++++++--------------------------
2 files changed, 13 insertions(+), 28 deletions(-)

diff --git a/docs/misc/arm/silicon-errata.txt b/docs/misc/arm/silicon-errata.txt
index c9854c39f4..906bf5fd48 100644
--- a/docs/misc/arm/silicon-errata.txt
+++ b/docs/misc/arm/silicon-errata.txt
@@ -48,3 +48,4 @@ stable hypervisors.
| ARM | Cortex-A57 | #852523 | N/A |
| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
+| ARM | MMU-500 | #842869 | N/A |
diff --git a/xen/drivers/passthrough/arm/smmu.c b/xen/drivers/passthrough/arm/smmu.c
index b51039943c..9612c0fddc 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -898,8 +898,7 @@ static void arm_smmu_tlb_inv_context(struct arm_smmu_domain *smmu_domain)

static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
{
- int flags, ret;
- u32 fsr, far, fsynr, resume;
+ u32 fsr, far, fsynr;
unsigned long iova;
struct iommu_domain *domain = dev;
struct arm_smmu_domain *smmu_domain = domain->priv;
@@ -913,13 +912,7 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
if (!(fsr & FSR_FAULT))
return IRQ_NONE;

- if (fsr & FSR_IGN)
- dev_err_ratelimited(smmu->dev,
- "Unexpected context fault (fsr 0x%x)\n",
- fsr);
-
fsynr = readl_relaxed(cb_base + ARM_SMMU_CB_FSYNR0);
- flags = fsynr & FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ;

far = readl_relaxed(cb_base + ARM_SMMU_CB_FAR_LO);
iova = far;
@@ -928,25 +921,12 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
iova |= ((unsigned long)far << 32);
#endif

- if (!report_iommu_fault(domain, smmu->dev, iova, flags)) {
- ret = IRQ_HANDLED;
- resume = RESUME_RETRY;
- } else {
- dev_err_ratelimited(smmu->dev,
- "Unhandled context fault: iova=0x%08lx, fsynr=0x%x, cb=%d\n",
- iova, fsynr, cfg->cbndx);
- ret = IRQ_NONE;
- resume = RESUME_TERMINATE;
- }
-
- /* Clear the faulting FSR */
+ dev_err_ratelimited(smmu->dev,
+ "Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cb=%d\n",
+ fsr, iova, fsynr, cfg->cbndx);
+
writel(fsr, cb_base + ARM_SMMU_CB_FSR);
-
- /* Retry or terminate any stalled transactions */
- if (fsr & FSR_SS)
- writel_relaxed(resume, cb_base + ARM_SMMU_CB_RESUME);
-
- return ret;
+ return IRQ_HANDLED;
}

static irqreturn_t arm_smmu_global_fault(int irq, void *dev)
@@ -1180,8 +1160,12 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain)
writel_relaxed(reg, cb_base + ARM_SMMU_CB_S1_MAIR0);
}

- /* SCTLR */
- reg = SCTLR_CFCFG | SCTLR_CFIE | SCTLR_CFRE | SCTLR_M | SCTLR_EAE_SBOP;
+ /*
+ * SCTLR
+ *
+ * Do not set SCTLR_CFCFG, because of Erratum #842869
+ */
+ reg = SCTLR_CFIE | SCTLR_CFRE | SCTLR_M | SCTLR_EAE_SBOP;
if (stage1)
reg |= SCTLR_S1_ASIDPNE;
#ifdef __BIG_ENDIAN
--
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