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powerpc/powernv/npu-dma: Add explicit flush when sending an ATSD
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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@popple.id.au>
[mpe: Use true/false for bool literals]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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Alistair Popple authored and Michael Ellerman committed Jun 22, 2017
1 parent bf05fc2 commit bbd5ff5
Showing 1 changed file with 65 additions and 29 deletions.
94 changes: 65 additions & 29 deletions arch/powerpc/platforms/powernv/npu-dma.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand All @@ -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;

Expand All @@ -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, true);
}
}

/*
* 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;

/*
Expand All @@ -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
Expand All @@ -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, false);
}

static void pnv_npu2_mn_release(struct mmu_notifier *mn,
Expand All @@ -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, true);
}

static void pnv_npu2_mn_change_pte(struct mmu_notifier *mn,
Expand All @@ -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, true);
}

static void pnv_npu2_mn_invalidate_page(struct mmu_notifier *mn,
Expand All @@ -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, true);
}

static void pnv_npu2_mn_invalidate_range(struct mmu_notifier *mn,
Expand All @@ -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, false);

/* Do the flush only on the final addess == end */
mmio_invalidate(npu_context, 1, address, true);
}

static const struct mmu_notifier_ops nv_nmmu_notifier_ops = {
Expand Down Expand Up @@ -651,8 +684,11 @@ 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);
}

Expand Down

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