From: Alexey Kardashevskiy <aik@ozlabs.ru> To: linuxppc-dev@lists.ozlabs.org Cc: Alistair Popple <alistair@popple.id.au>, "Oliver O'Halloran" <oohall@gmail.com>, David Gibson <david@gibson.dropbear.id.au>, Sam Bobroff <sbobroff@linux.ibm.com>, Alexey Kardashevskiy <aik@ozlabs.ru>, stable@vger.kernel.org Subject: [PATCH kernel v5 1/4] powerpc/powernv/ioda: Fix race in TCE level allocation Date: Thu, 18 Jul 2019 15:11:36 +1000 [thread overview] Message-ID: <20190718051139.74787-2-aik@ozlabs.ru> (raw) In-Reply-To: <20190718051139.74787-1-aik@ozlabs.ru> 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 cmpxchg to handle the race. Note that once TCE is non-zero, it cannot become zero again. CC: stable@vger.kernel.org # v4.19+ Fixes: a68bd1267b72 ("powerpc/powernv/ioda: Allocate indirect TCE levels on demand") Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- The race occurs about 30 times in the first 3 minutes of copying files via rsync and that's about it. This fixes EEH's from https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=110810 --- Changes: v2: * replaced spin_lock with cmpxchg+readonce --- arch/powerpc/platforms/powernv/pci-ioda-tce.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c b/arch/powerpc/platforms/powernv/pci-ioda-tce.c index e28f03e1eb5e..8d6569590161 100644 --- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c +++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c @@ -48,6 +48,9 @@ static __be64 *pnv_alloc_tce_level(int nid, unsigned int shift) return addr; } +static void pnv_pci_ioda2_table_do_free_pages(__be64 *addr, + unsigned long size, unsigned int levels); + static __be64 *pnv_tce(struct iommu_table *tbl, bool user, long idx, bool alloc) { __be64 *tmp = user ? tbl->it_userspace : (__be64 *) tbl->it_base; @@ -57,9 +60,9 @@ static __be64 *pnv_tce(struct iommu_table *tbl, bool user, long idx, bool alloc) while (level) { int n = (idx & mask) >> (level * shift); - unsigned long tce; + unsigned long oldtce, tce = be64_to_cpu(READ_ONCE(tmp[n])); - if (tmp[n] == 0) { + if (!tce) { __be64 *tmp2; if (!alloc) @@ -70,10 +73,15 @@ static __be64 *pnv_tce(struct iommu_table *tbl, bool user, long idx, bool alloc) if (!tmp2) return NULL; - tmp[n] = cpu_to_be64(__pa(tmp2) | - TCE_PCI_READ | TCE_PCI_WRITE); + tce = __pa(tmp2) | TCE_PCI_READ | TCE_PCI_WRITE; + oldtce = be64_to_cpu(cmpxchg(&tmp[n], 0, + cpu_to_be64(tce))); + if (oldtce) { + pnv_pci_ioda2_table_do_free_pages(tmp2, + ilog2(tbl->it_level_size) + 3, 1); + tce = oldtce; + } } - tce = be64_to_cpu(tmp[n]); tmp = __va(tce & ~(TCE_PCI_READ | TCE_PCI_WRITE)); idx &= ~mask; -- 2.17.1
WARNING: multiple messages have this Message-ID (diff)
From: Alexey Kardashevskiy <aik@ozlabs.ru> To: linuxppc-dev@lists.ozlabs.org Cc: Sam Bobroff <sbobroff@linux.ibm.com>, Alistair Popple <alistair@popple.id.au>, stable@vger.kernel.org, Alexey Kardashevskiy <aik@ozlabs.ru>, Oliver O'Halloran <oohall@gmail.com>, David Gibson <david@gibson.dropbear.id.au> Subject: [PATCH kernel v5 1/4] powerpc/powernv/ioda: Fix race in TCE level allocation Date: Thu, 18 Jul 2019 15:11:36 +1000 [thread overview] Message-ID: <20190718051139.74787-2-aik@ozlabs.ru> (raw) In-Reply-To: <20190718051139.74787-1-aik@ozlabs.ru> 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 cmpxchg to handle the race. Note that once TCE is non-zero, it cannot become zero again. CC: stable@vger.kernel.org # v4.19+ Fixes: a68bd1267b72 ("powerpc/powernv/ioda: Allocate indirect TCE levels on demand") Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- The race occurs about 30 times in the first 3 minutes of copying files via rsync and that's about it. This fixes EEH's from https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=110810 --- Changes: v2: * replaced spin_lock with cmpxchg+readonce --- arch/powerpc/platforms/powernv/pci-ioda-tce.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c b/arch/powerpc/platforms/powernv/pci-ioda-tce.c index e28f03e1eb5e..8d6569590161 100644 --- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c +++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c @@ -48,6 +48,9 @@ static __be64 *pnv_alloc_tce_level(int nid, unsigned int shift) return addr; } +static void pnv_pci_ioda2_table_do_free_pages(__be64 *addr, + unsigned long size, unsigned int levels); + static __be64 *pnv_tce(struct iommu_table *tbl, bool user, long idx, bool alloc) { __be64 *tmp = user ? tbl->it_userspace : (__be64 *) tbl->it_base; @@ -57,9 +60,9 @@ static __be64 *pnv_tce(struct iommu_table *tbl, bool user, long idx, bool alloc) while (level) { int n = (idx & mask) >> (level * shift); - unsigned long tce; + unsigned long oldtce, tce = be64_to_cpu(READ_ONCE(tmp[n])); - if (tmp[n] == 0) { + if (!tce) { __be64 *tmp2; if (!alloc) @@ -70,10 +73,15 @@ static __be64 *pnv_tce(struct iommu_table *tbl, bool user, long idx, bool alloc) if (!tmp2) return NULL; - tmp[n] = cpu_to_be64(__pa(tmp2) | - TCE_PCI_READ | TCE_PCI_WRITE); + tce = __pa(tmp2) | TCE_PCI_READ | TCE_PCI_WRITE; + oldtce = be64_to_cpu(cmpxchg(&tmp[n], 0, + cpu_to_be64(tce))); + if (oldtce) { + pnv_pci_ioda2_table_do_free_pages(tmp2, + ilog2(tbl->it_level_size) + 3, 1); + tce = oldtce; + } } - tce = be64_to_cpu(tmp[n]); tmp = __va(tce & ~(TCE_PCI_READ | TCE_PCI_WRITE)); idx &= ~mask; -- 2.17.1
next prev parent reply other threads:[~2019-07-18 5:11 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-07-18 5:11 [PATCH kernel v5 0/4] powerpc/ioda2: Yet another attempt to allow DMA masks between 32 and 59 Alexey Kardashevskiy 2019-07-18 5:11 ` Alexey Kardashevskiy [this message] 2019-07-18 5:11 ` [PATCH kernel v5 1/4] powerpc/powernv/ioda: Fix race in TCE level allocation Alexey Kardashevskiy 2019-08-22 13:08 ` Michael Ellerman 2019-07-18 5:11 ` [PATCH kernel v5 2/4] powerpc/iommu: Allow bypass-only for DMA Alexey Kardashevskiy 2019-07-18 5:11 ` [PATCH kernel v5 3/4] powerpc/powernv/ioda2: Allocate TCE table levels on demand for default DMA window Alexey Kardashevskiy 2019-07-18 5:11 ` [PATCH kernel v5 4/4] powerpc/powernv/ioda2: Create bigger default window with 64k IOMMU pages Alexey Kardashevskiy
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