* Re: [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic
2022-05-23 11:26 [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic Kefeng Wang
@ 2022-05-23 11:19 ` Kefeng Wang
2022-05-23 11:26 ` [PATCH v4 1/2] asm-generic: Add memory barrier dma_mb() Kefeng Wang
2022-05-23 11:26 ` [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers Kefeng Wang
2 siblings, 0 replies; 6+ messages in thread
From: Kefeng Wang @ 2022-05-23 11:19 UTC (permalink / raw)
To: catalin.marinas, will, akpm, linux-arm-kernel, linux-kernel
Cc: linux-mm, hch, arnd, anshuman.khandual
Sorry for using wrong script with uncorrected maintainers, please ignore.
On 2022/5/23 19:26, Kefeng Wang wrote:
> Fix selftest and kcsan_test() module fail when KCSAN_STRICT
> and KCSAN_WEAK_MEMORY enabled on ARM64.
>
> v4:
> - Use 2 spaces after a sentence-ending '.', suggested by Marco
> - Collect Ack/Review
>
> v3:
> - update dma_mb()'s description and add the generic definition,
> also asm-generic change is moved into patch1, suggested by Marco.
> v2:
> - Add documents about dma_mb(), suggested by Mike and Will.
> - drop Fixes tag and update changlog, suggested by Mike.
>
>
> Kefeng Wang (2):
> asm-generic: Add memory barrier dma_mb()
> arm64: kcsan: Support detecting more missing memory barriers
>
> Documentation/memory-barriers.txt | 11 ++++++-----
> arch/arm64/include/asm/barrier.h | 12 ++++++------
> include/asm-generic/barrier.h | 8 ++++++++
> 3 files changed, 20 insertions(+), 11 deletions(-)
>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic
@ 2022-05-23 11:26 Kefeng Wang
2022-05-23 11:19 ` Kefeng Wang
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Kefeng Wang @ 2022-05-23 11:26 UTC (permalink / raw)
To: catalin.marinas, will, akpm, linux-arm-kernel, linux-kernel
Cc: linux-mm, hch, arnd, anshuman.khandual, Kefeng Wang
Fix selftest and kcsan_test() module fail when KCSAN_STRICT
and KCSAN_WEAK_MEMORY enabled on ARM64.
v4:
- Use 2 spaces after a sentence-ending '.', suggested by Marco
- Collect Ack/Review
v3:
- update dma_mb()'s description and add the generic definition,
also asm-generic change is moved into patch1, suggested by Marco.
v2:
- Add documents about dma_mb(), suggested by Mike and Will.
- drop Fixes tag and update changlog, suggested by Mike.
Kefeng Wang (2):
asm-generic: Add memory barrier dma_mb()
arm64: kcsan: Support detecting more missing memory barriers
Documentation/memory-barriers.txt | 11 ++++++-----
arch/arm64/include/asm/barrier.h | 12 ++++++------
include/asm-generic/barrier.h | 8 ++++++++
3 files changed, 20 insertions(+), 11 deletions(-)
--
2.35.3
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v4 1/2] asm-generic: Add memory barrier dma_mb()
2022-05-23 11:26 [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic Kefeng Wang
2022-05-23 11:19 ` Kefeng Wang
@ 2022-05-23 11:26 ` Kefeng Wang
2022-05-23 11:26 ` [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers Kefeng Wang
2 siblings, 0 replies; 6+ messages in thread
From: Kefeng Wang @ 2022-05-23 11:26 UTC (permalink / raw)
To: catalin.marinas, will, akpm, linux-arm-kernel, linux-kernel
Cc: linux-mm, hch, arnd, anshuman.khandual, Kefeng Wang
The memory barrier dma_mb() is introduced by commit a76a37777f2c
("iommu/arm-smmu-v3: Ensure queue is read after updating prod pointer"),
which is used to ensure that prior (both reads and writes) accesses
to memory by a CPU are ordered w.r.t. a subsequent MMIO write.
Reviewed-by: Arnd Bergmann <arnd@arndb.de> # for asm-generic
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
Documentation/memory-barriers.txt | 11 ++++++-----
include/asm-generic/barrier.h | 8 ++++++++
2 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index b12df9137e1c..832b5d36e279 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1894,6 +1894,7 @@ There are some more advanced barrier functions:
(*) dma_wmb();
(*) dma_rmb();
+ (*) dma_mb();
These are for use with consistent memory to guarantee the ordering
of writes or reads of shared memory accessible to both the CPU and a
@@ -1925,11 +1926,11 @@ There are some more advanced barrier functions:
The dma_rmb() allows us guarantee the device has released ownership
before we read the data from the descriptor, and the dma_wmb() allows
us to guarantee the data is written to the descriptor before the device
- can see it now has ownership. Note that, when using writel(), a prior
- wmb() is not needed to guarantee that the cache coherent memory writes
- have completed before writing to the MMIO region. The cheaper
- writel_relaxed() does not provide this guarantee and must not be used
- here.
+ can see it now has ownership. The dma_mb() implies both a dma_rmb() and
+ a dma_wmb(). Note that, when using writel(), a prior wmb() is not needed
+ to guarantee that the cache coherent memory writes have completed before
+ writing to the MMIO region. The cheaper writel_relaxed() does not provide
+ this guarantee and must not be used here.
See the subsection "Kernel I/O barrier effects" for more information on
relaxed I/O accessors and the Documentation/core-api/dma-api.rst file for
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index fd7e8fbaeef1..961f4d88f9ef 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -38,6 +38,10 @@
#define wmb() do { kcsan_wmb(); __wmb(); } while (0)
#endif
+#ifdef __dma_mb
+#define dma_mb() do { kcsan_mb(); __dma_mb(); } while (0)
+#endif
+
#ifdef __dma_rmb
#define dma_rmb() do { kcsan_rmb(); __dma_rmb(); } while (0)
#endif
@@ -65,6 +69,10 @@
#define wmb() mb()
#endif
+#ifndef dma_mb
+#define dma_mb() mb()
+#endif
+
#ifndef dma_rmb
#define dma_rmb() rmb()
#endif
--
2.35.3
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers
2022-05-23 11:26 [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic Kefeng Wang
2022-05-23 11:19 ` Kefeng Wang
2022-05-23 11:26 ` [PATCH v4 1/2] asm-generic: Add memory barrier dma_mb() Kefeng Wang
@ 2022-05-23 11:26 ` Kefeng Wang
2 siblings, 0 replies; 6+ messages in thread
From: Kefeng Wang @ 2022-05-23 11:26 UTC (permalink / raw)
To: catalin.marinas, will, akpm, linux-arm-kernel, linux-kernel
Cc: linux-mm, hch, arnd, anshuman.khandual, Kefeng Wang, Marco Elver
As "kcsan: Support detecting a subset of missing memory barriers"[1]
introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
more missing memory barrier, but arm64 don't have KCSAN instrumentation
for barriers, so the new selftest test_barrier() and test cases for
memory barrier instrumentation in kcsan_test module will fail, even
panic on selftest.
Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
defined the final instrumented version of these barriers, which will
fix the above issues.
Note, barrier instrumentation that can be disabled via __no_kcsan with
appropriate compiler-support (and not just with objtool help), see
commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
objtool support exists"), it adds disable_sanitizer_instrumentation to
__no_kcsan attribute which will remove all sanitizer instrumentation fully
(with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
[1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
arch/arm64/include/asm/barrier.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 9f3e2c3d2ca0..2cfc4245d2e2 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -50,13 +50,13 @@
#define pmr_sync() do {} while (0)
#endif
-#define mb() dsb(sy)
-#define rmb() dsb(ld)
-#define wmb() dsb(st)
+#define __mb() dsb(sy)
+#define __rmb() dsb(ld)
+#define __wmb() dsb(st)
-#define dma_mb() dmb(osh)
-#define dma_rmb() dmb(oshld)
-#define dma_wmb() dmb(oshst)
+#define __dma_mb() dmb(osh)
+#define __dma_rmb() dmb(oshld)
+#define __dma_wmb() dmb(oshst)
#define io_stop_wc() dgh()
--
2.35.3
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic
2022-05-23 11:31 [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic Kefeng Wang
@ 2022-06-23 19:31 ` Will Deacon
0 siblings, 0 replies; 6+ messages in thread
From: Will Deacon @ 2022-06-23 19:31 UTC (permalink / raw)
To: elver, Jonathan Corbet, linux-kernel, Kefeng Wang, mark.rutland,
catalin.marinas, linux-arm-kernel
Cc: kernel-team, Will Deacon, arnd, linux-doc
On Mon, 23 May 2022 19:31:24 +0800, Kefeng Wang wrote:
> Fix selftest and kcsan_test() module fail when KCSAN_STRICT
> and KCSAN_WEAK_MEMORY enabled on ARM64.
>
> v4:
> - Use 2 spaces after a sentence-ending '.', suggested by Marco
> - Collect Ack/Review
>
> [...]
Applied to arm64 (for-next/kcsan), thanks!
[1/2] asm-generic: Add memory barrier dma_mb()
https://git.kernel.org/arm64/c/ed59dfd9509d
[2/2] arm64: kcsan: Support detecting more missing memory barriers
https://git.kernel.org/arm64/c/4d09caec2fab
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic
@ 2022-05-23 11:31 Kefeng Wang
2022-06-23 19:31 ` Will Deacon
0 siblings, 1 reply; 6+ messages in thread
From: Kefeng Wang @ 2022-05-23 11:31 UTC (permalink / raw)
To: elver, catalin.marinas, will, linux-arm-kernel, linux-kernel,
mark.rutland, Jonathan Corbet
Cc: linux-doc, arnd, Kefeng Wang
Fix selftest and kcsan_test() module fail when KCSAN_STRICT
and KCSAN_WEAK_MEMORY enabled on ARM64.
v4:
- Use 2 spaces after a sentence-ending '.', suggested by Marco
- Collect Ack/Review
v3:
- update dma_mb()'s description and add the generic definition,
also asm-generic change is moved into patch1, suggested by Marco.
v2:
- Add documents about dma_mb(), suggested by Mike and Will.
- drop Fixes tag and update changlog, suggested by Mike.
Kefeng Wang (2):
asm-generic: Add memory barrier dma_mb()
arm64: kcsan: Support detecting more missing memory barriers
Documentation/memory-barriers.txt | 11 ++++++-----
arch/arm64/include/asm/barrier.h | 12 ++++++------
include/asm-generic/barrier.h | 8 ++++++++
3 files changed, 20 insertions(+), 11 deletions(-)
--
2.35.3
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 6+ messages in thread
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2022-05-23 11:26 [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic Kefeng Wang
2022-05-23 11:19 ` Kefeng Wang
2022-05-23 11:26 ` [PATCH v4 1/2] asm-generic: Add memory barrier dma_mb() Kefeng Wang
2022-05-23 11:26 ` [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers Kefeng Wang
2022-05-23 11:31 [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic Kefeng Wang
2022-06-23 19:31 ` Will Deacon
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