[PATCH 2/2] powernv/npu: Prevent overwriting of pnv_npu2_init_contex() callback parameters

[Alistair Popple]

There is a single npu context per set of callback parameters. Callers
should be prevented from overwriting existing callback values so instead
return an error if different parameters are passed.

Signed-off-by: Alistair Popple <alist...@popple.id.au>
---
 arch/powerpc/include/asm/powernv.h       |  2 +-
 arch/powerpc/platforms/powernv/npu-dma.c | 16 +++++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/powernv.h 
b/arch/powerpc/include/asm/powernv.h
index dc5f6a5d4575..362ea12a4501 100644
--- a/arch/powerpc/include/asm/powernv.h
+++ b/arch/powerpc/include/asm/powernv.h
@@ -15,7 +15,7 @@
 extern void powernv_set_nmmu_ptcr(unsigned long ptcr);
 extern struct npu_context *pnv_npu2_init_context(struct pci_dev *gpdev,
                        unsigned long flags,
-                       struct npu_context *(*cb)(struct npu_context *, void *),
+                       void (*cb)(struct npu_context *, void *),
                        void *priv);
 extern void pnv_npu2_destroy_context(struct npu_context *context,
                                struct pci_dev *gpdev);
diff --git a/arch/powerpc/platforms/powernv/npu-dma.c 
b/arch/powerpc/platforms/powernv/npu-dma.c
index cb77162f4e7a..193f43ea3fbc 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c
@@ -407,7 +407,7 @@ struct npu_context {
        bool nmmu_flush;
 
        /* Callback to stop translation requests on a given GPU */
-       struct npu_context *(*release_cb)(struct npu_context *, void *);
+       void (*release_cb)(struct npu_context *context, void *priv);
 
        /*
         * Private pointer passed to the above callback for usage by
@@ -705,7 +705,7 @@ static const struct mmu_notifier_ops nv_nmmu_notifier_ops = 
{
  */
 struct npu_context *pnv_npu2_init_context(struct pci_dev *gpdev,
                        unsigned long flags,
-                       struct npu_context *(*cb)(struct npu_context *, void *),
+                       void (*cb)(struct npu_context *, void *),
                        void *priv)
 {
        int rc;
@@ -763,8 +763,18 @@ struct npu_context *pnv_npu2_init_context(struct pci_dev 
*gpdev,
         */
        spin_lock(&npu_context_lock);
        npu_context = mm->context.npu_context;
-       if (npu_context)
+       if (npu_context) {
+               if (npu_context->release_cb != cb ||
+                       npu_context->priv != priv) {
+                       spin_unlock(&npu_context_lock);
+                       opal_npu_destroy_context(nphb->opal_id, mm->context.id,
+                                               PCI_DEVID(gpdev->bus->number,
+                                                       gpdev->devfn));
+                       return ERR_PTR(-EINVAL);
+               }
+
                WARN_ON(!kref_get_unless_zero(&npu_context->kref));
+       }
        spin_unlock(&npu_context_lock);
 
        if (!npu_context) {
-- 
2.11.0