The nest mmu required an explicit flush as a tlbi would not flush it in the
same way as the core. However an alternate firmware fix exists which should
eliminate the need for this flush, so instead add a device-tree property
(ibm,nmmu-flush) on the NVLink2 PHB to enable it only if required.
Signed-off-by: Alistair Popple <alist...@popple.id.au>
---
arch/powerpc/platforms/powernv/npu-dma.c | 28 +++++++++++++++++++++++-----
arch/powerpc/platforms/powernv/pci.h | 3 +++
2 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/platforms/powernv/npu-dma.c
b/arch/powerpc/platforms/powernv/npu-dma.c
index 2fff9a65..4b4fcac 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c
@@ -395,6 +395,7 @@ struct npu_context {
struct pci_dev *npdev[NV_MAX_NPUS][NV_MAX_LINKS];
struct mmu_notifier mn;
struct kref kref;
+ bool nmmu_flush;
/* Callback to stop translation requests on a given GPU */
struct npu_context *(*release_cb)(struct npu_context *, void *);
@@ -545,11 +546,13 @@ static void mmio_invalidate(struct npu_context
*npu_context, int va,
struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS];
unsigned long pid = npu_context->mm->context.id;
- /*
- * Unfortunately the nest mmu does not support flushing specific
- * addresses so we have to flush the whole mm.
- */
- flush_all_mm(npu_context->mm);
+ if (npu_context->nmmu_flush)
+ /*
+ * Unfortunately the nest mmu does not support flushing specific
+ * addresses so we have to flush the whole mm once before
+ * shooting down the GPU translation.
+ */
+ flush_all_mm(npu_context->mm);
/*
* Loop over all the NPUs this process is active on and launch
@@ -722,6 +725,16 @@ struct npu_context *pnv_npu2_init_context(struct pci_dev
*gpdev,
return ERR_PTR(-ENODEV);
npu_context->npdev[npu->index][nvlink_index] = npdev;
+ if (!nphb->npu.nmmu_flush) {
+ /*
+ * If we're not explicitly flushing ourselves we need to mark
+ * the thread for global flushes
+ */
+ npu_context->nmmu_flush = false;
+ inc_mm_active_cpus(mm);
+ } else
+ npu_context->nmmu_flush = true;
+
return npu_context;
}
EXPORT_SYMBOL(pnv_npu2_init_context);
@@ -731,6 +744,9 @@ static void pnv_npu2_release_context(struct kref *kref)
struct npu_context *npu_context =
container_of(kref, struct npu_context, kref);
+ if (!npu_context->nmmu_flush)
+ dec_mm_active_cpus(npu_context->mm);
+
npu_context->mm->context.npu_context = NULL;
mmu_notifier_unregister(&npu_context->mn,
npu_context->mm);
@@ -819,6 +835,8 @@ int pnv_npu2_init(struct pnv_phb *phb)
static int npu_index;
uint64_t rc = 0;
+ phb->npu.nmmu_flush =
+ of_property_read_bool(phb->hose->dn, "ibm,nmmu-flush");
for_each_child_of_node(phb->hose->dn, dn) {
gpdev = pnv_pci_get_gpu_dev(get_pci_dev(dn));
if (gpdev) {
diff --git a/arch/powerpc/platforms/powernv/pci.h
b/arch/powerpc/platforms/powernv/pci.h
index a95273c..22025c6 100644
--- a/arch/powerpc/platforms/powernv/pci.h
+++ b/arch/powerpc/platforms/powernv/pci.h
@@ -187,6 +187,9 @@ struct pnv_phb {
/* Bitmask for MMIO register usage */
unsigned long mmio_atsd_usage;
+
+ /* Do we need to explicitly flush the nest mmu? */
+ bool nmmu_flush;
} npu;
#ifdef CONFIG_CXL_BASE
--
2.1.4
