[PATCH] powernv/npu-dma.c: Add explicit flush when sending an ATSD
Alistair Popple
alistair at popple.id.au
Tue Jun 20 18:37:28 AEST 2017
NPU2 requires an extra explicit flush to an active GPU PID when sending
address translation shoot downs (ATSDs) to reliably flush the GPU TLB. This
patch adds just such a flush at the end of each sequence of ATSDs.
We can safely use PID 0 which is always reserved and active on the GPU. PID
0 is only used for init_mm which will never be a user mm on the GPU. To
enforce this we add a check in pnv_npu2_init_context() just in case someone
tries to use PID 0 on the GPU.
Signed-off-by: Alistair Popple <alistair at popple.id.au>
---
Michael,
It turns out my assumptions about MMU_NO_CONTEXT were wrong so we have
reverted to using HW context id/PID 0 (init_mm) as that is quite clearly
reserved on hash and radix and it seems unlikely PID 0 would ever be used
for anything else.
That said if you feel strongly it would be easy enough to add functions to
reserve a PID and an exported function for device drivers to call to find
out what the reserved PID is. I was avoiding it because it would be more
invasive adding code and an external API for something that I'm not sure
will ever change, although if it does there is a check in
pnv2_npu2_init_context() to flag it so it won't result in weird bugs.
Anyway let me know which way you would like us to go here and I can update
the patch as required, thanks!
- Alistair
arch/powerpc/platforms/powernv/npu-dma.c | 93 ++++++++++++++++++++++----------
1 file changed, 64 insertions(+), 29 deletions(-)
diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
index e6f444b..9468064 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c
@@ -449,7 +449,7 @@ static int mmio_launch_invalidate(struct npu *npu, unsigned long launch,
return mmio_atsd_reg;
}
-static int mmio_invalidate_pid(struct npu *npu, unsigned long pid)
+static int mmio_invalidate_pid(struct npu *npu, unsigned long pid, bool flush)
{
unsigned long launch;
@@ -465,12 +465,15 @@ static int mmio_invalidate_pid(struct npu *npu, unsigned long pid)
/* PID */
launch |= pid << PPC_BITLSHIFT(38);
+ /* No flush */
+ launch |= !flush << PPC_BITLSHIFT(39);
+
/* Invalidating the entire process doesn't use a va */
return mmio_launch_invalidate(npu, launch, 0);
}
static int mmio_invalidate_va(struct npu *npu, unsigned long va,
- unsigned long pid)
+ unsigned long pid, bool flush)
{
unsigned long launch;
@@ -486,26 +489,60 @@ static int mmio_invalidate_va(struct npu *npu, unsigned long va,
/* PID */
launch |= pid << PPC_BITLSHIFT(38);
+ /* No flush */
+ launch |= !flush << PPC_BITLSHIFT(39);
+
return mmio_launch_invalidate(npu, launch, va);
}
#define mn_to_npu_context(x) container_of(x, struct npu_context, mn)
+struct mmio_atsd_reg {
+ struct npu *npu;
+ int reg;
+};
+
+static void mmio_invalidate_wait(
+ struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS], bool flush)
+{
+ struct npu *npu;
+ int i, reg;
+
+ /* Wait for all invalidations to complete */
+ for (i = 0; i <= max_npu2_index; i++) {
+ if (mmio_atsd_reg[i].reg < 0)
+ continue;
+
+ /* Wait for completion */
+ npu = mmio_atsd_reg[i].npu;
+ reg = mmio_atsd_reg[i].reg;
+ while (__raw_readq(npu->mmio_atsd_regs[reg] + XTS_ATSD_STAT))
+ cpu_relax();
+
+ put_mmio_atsd_reg(npu, reg);
+
+ /*
+ * The GPU requires two flush ATSDs to ensure all entries have
+ * been flushed. We use PID 0 as it will never be used for a
+ * process on the GPU.
+ */
+ if (flush)
+ mmio_invalidate_pid(npu, 0, 1);
+ }
+}
+
/*
* Invalidate either a single address or an entire PID depending on
* the value of va.
*/
static void mmio_invalidate(struct npu_context *npu_context, int va,
- unsigned long address)
+ unsigned long address, bool flush)
{
- int i, j, reg;
+ int i, j;
struct npu *npu;
struct pnv_phb *nphb;
struct pci_dev *npdev;
- struct {
- struct npu *npu;
- int reg;
- } mmio_atsd_reg[NV_MAX_NPUS];
+ struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS];
unsigned long pid = npu_context->mm->context.id;
/*
@@ -525,10 +562,11 @@ static void mmio_invalidate(struct npu_context *npu_context, int va,
if (va)
mmio_atsd_reg[i].reg =
- mmio_invalidate_va(npu, address, pid);
+ mmio_invalidate_va(npu, address, pid,
+ flush);
else
mmio_atsd_reg[i].reg =
- mmio_invalidate_pid(npu, pid);
+ mmio_invalidate_pid(npu, pid, flush);
/*
* The NPU hardware forwards the shootdown to all GPUs
@@ -544,18 +582,10 @@ static void mmio_invalidate(struct npu_context *npu_context, int va,
*/
flush_tlb_mm(npu_context->mm);
- /* Wait for all invalidations to complete */
- for (i = 0; i <= max_npu2_index; i++) {
- if (mmio_atsd_reg[i].reg < 0)
- continue;
-
- /* Wait for completion */
- npu = mmio_atsd_reg[i].npu;
- reg = mmio_atsd_reg[i].reg;
- while (__raw_readq(npu->mmio_atsd_regs[reg] + XTS_ATSD_STAT))
- cpu_relax();
- put_mmio_atsd_reg(npu, reg);
- }
+ mmio_invalidate_wait(mmio_atsd_reg, flush);
+ if (flush)
+ /* Wait for the flush to complete */
+ mmio_invalidate_wait(mmio_atsd_reg, 0);
}
static void pnv_npu2_mn_release(struct mmu_notifier *mn,
@@ -571,7 +601,7 @@ static void pnv_npu2_mn_release(struct mmu_notifier *mn,
* There should be no more translation requests for this PID, but we
* need to ensure any entries for it are removed from the TLB.
*/
- mmio_invalidate(npu_context, 0, 0);
+ mmio_invalidate(npu_context, 0, 0, 1);
}
static void pnv_npu2_mn_change_pte(struct mmu_notifier *mn,
@@ -581,7 +611,7 @@ static void pnv_npu2_mn_change_pte(struct mmu_notifier *mn,
{
struct npu_context *npu_context = mn_to_npu_context(mn);
- mmio_invalidate(npu_context, 1, address);
+ mmio_invalidate(npu_context, 1, address, 1);
}
static void pnv_npu2_mn_invalidate_page(struct mmu_notifier *mn,
@@ -590,7 +620,7 @@ static void pnv_npu2_mn_invalidate_page(struct mmu_notifier *mn,
{
struct npu_context *npu_context = mn_to_npu_context(mn);
- mmio_invalidate(npu_context, 1, address);
+ mmio_invalidate(npu_context, 1, address, 1);
}
static void pnv_npu2_mn_invalidate_range(struct mmu_notifier *mn,
@@ -600,8 +630,11 @@ static void pnv_npu2_mn_invalidate_range(struct mmu_notifier *mn,
struct npu_context *npu_context = mn_to_npu_context(mn);
unsigned long address;
- for (address = start; address <= end; address += PAGE_SIZE)
- mmio_invalidate(npu_context, 1, address);
+ for (address = start; address < end; address += PAGE_SIZE)
+ mmio_invalidate(npu_context, 1, address, 0);
+
+ /* Do the flush only on the final addess == end */
+ mmio_invalidate(npu_context, 1, address, 1);
}
static const struct mmu_notifier_ops nv_nmmu_notifier_ops = {
@@ -651,8 +684,10 @@ struct npu_context *pnv_npu2_init_context(struct pci_dev *gpdev,
/* No nvlink associated with this GPU device */
return ERR_PTR(-ENODEV);
- if (!mm) {
- /* kernel thread contexts are not supported */
+ if (!mm || mm->context.id == 0) {
+ /* kernel thread contexts are not supported and context id 0 is
+ * reserved on the GPU.
+ */
return ERR_PTR(-EINVAL);
}
--
2.1.4
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