pnv_tce() returns a pointer to a TCE entry and originally a TCE table
would be pre-allocated. For the default case of 2GB window the table
needs only a single level and that is fine. However if more levels are
requested, it is possible to get a race when 2 threads want a pointer
to a TCE entry from the same page of TCEs.
This adds a spinlock to handle the race. The alloc==true case is not
possible in the real mode so spinlock is safe for KVM as well.
CC: sta...@vger.kernel.org # v4.19+
Fixes: a68bd1267b72 ("powerpc/powernv/ioda: Allocate indirect TCE levels on
demand")
Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
---
This fixes EEH's from
https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=110810
---
arch/powerpc/include/asm/iommu.h | 1 +
arch/powerpc/platforms/powernv/pci-ioda-tce.c | 21 ++++++++++++-------
2 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index 2c1845e5e851..1825b4cc0097 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -111,6 +111,7 @@ struct iommu_table {
struct iommu_table_ops *it_ops;
struct kref it_kref;
int it_nid;
+ spinlock_t it_lock;
};
#define IOMMU_TABLE_USERSPACE_ENTRY_RO(tbl, entry) \
diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c
b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
index e28f03e1eb5e..9a19d61e2b12 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
@@ -29,6 +29,7 @@ void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
tbl->it_size = tce_size >> 3;
tbl->it_busno = 0;
tbl->it_type = TCE_PCI;
+ spin_lock_init(&tbl->it_lock);
}
static __be64 *pnv_alloc_tce_level(int nid, unsigned int shift)
@@ -60,18 +61,22 @@ static __be64 *pnv_tce(struct iommu_table *tbl, bool user,
long idx, bool alloc)
unsigned long tce;
if (tmp[n] == 0) {
- __be64 *tmp2;
-
if (!alloc)
return NULL;
- tmp2 = pnv_alloc_tce_level(tbl->it_nid,
- ilog2(tbl->it_level_size) + 3);
- if (!tmp2)
- return NULL;
+ spin_lock(&tbl->it_lock);
+ if (tmp[n] == 0) {
+ __be64 *tmp2;
- tmp[n] = cpu_to_be64(__pa(tmp2) |
- TCE_PCI_READ | TCE_PCI_WRITE);
+ tmp2 = pnv_alloc_tce_level(tbl->it_nid,
+ ilog2(tbl->it_level_size) + 3);
+ if (tmp2)
+ tmp[n] = cpu_to_be64(__pa(tmp2) |
+ TCE_PCI_READ | TCE_PCI_WRITE);
+ }
+ spin_unlock(&tbl->it_lock);
+ if (tmp[n] == 0)
+ return NULL;
}
tce = be64_to_cpu(tmp[n]);
--
2.17.1
