* [PATCH v1 0/4] arm64/sme: SME related fixes
@ 2022-08-11 10:57 Mark Brown
2022-08-11 10:57 ` [PATCH v1 1/4] arm64/signal: Raise limit on stack frames Mark Brown
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: Mark Brown @ 2022-08-11 10:57 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon; +Cc: linux-arm-kernel, Mark Brown
This series collates together a number of SME related fixes that have
come up in testing.
Mark Brown (4):
arm64/signal: Raise limit on stack frames
arm64/signal: Flush FPSIMD register state when disabling streaming
mode
arm64/sme: Don't flush SVE register state when allocating SME storage
arm64/sme: Don't flush SVE register state when handling SME traps
arch/arm64/include/asm/fpsimd.h | 2 +-
arch/arm64/kernel/fpsimd.c | 21 ++++++---------------
arch/arm64/kernel/ptrace.c | 6 +++---
arch/arm64/kernel/signal.c | 14 ++++++++++++--
4 files changed, 22 insertions(+), 21 deletions(-)
base-commit: a111daf0c53ae91e71fd2bfe7497862d14132e3e
--
2.30.2
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^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v1 1/4] arm64/signal: Raise limit on stack frames
2022-08-11 10:57 [PATCH v1 0/4] arm64/sme: SME related fixes Mark Brown
@ 2022-08-11 10:57 ` Mark Brown
2022-08-11 10:57 ` [PATCH v1 2/4] arm64/signal: Flush FPSIMD register state when disabling streaming mode Mark Brown
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Mark Brown @ 2022-08-11 10:57 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon; +Cc: linux-arm-kernel, Mark Brown
The signal code has a limit of 64K on the size of a stack frame that it
will generate, if this limit is exceeded then a process will be killed if
it receives a signal. Unfortunately with the advent of SME this limit is
too small - the maximum possible size of the ZA register alone is 64K. This
is not an issue for practical systems at present but is easily seen using
virtual platforms.
Raise the limit to 256K, this is substantially more than could be used by
any current architecture extension.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kernel/signal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index b0980fbb6bc7..13dee9cedfc6 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -91,7 +91,7 @@ static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
* not taken into account. This limit is not a guarantee and is
* NOT ABI.
*/
-#define SIGFRAME_MAXSZ SZ_64K
+#define SIGFRAME_MAXSZ (SZ_64K * 4)
static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
unsigned long *offset, size_t size, bool extend)
--
2.30.2
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v1 2/4] arm64/signal: Flush FPSIMD register state when disabling streaming mode
2022-08-11 10:57 [PATCH v1 0/4] arm64/sme: SME related fixes Mark Brown
2022-08-11 10:57 ` [PATCH v1 1/4] arm64/signal: Raise limit on stack frames Mark Brown
@ 2022-08-11 10:57 ` Mark Brown
2022-08-11 10:57 ` [PATCH v1 3/4] arm64/sme: Don't flush SVE register state when allocating SME storage Mark Brown
2022-08-11 10:57 ` [PATCH v1 4/4] arm64/sme: Don't flush SVE register state when handling SME traps Mark Brown
3 siblings, 0 replies; 5+ messages in thread
From: Mark Brown @ 2022-08-11 10:57 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon; +Cc: linux-arm-kernel, Mark Brown
When handling a signal delivered to a context with streaming mode enabled
we will disable streaming mode for the signal handler, when doing so we
should also flush the saved FPSIMD register state like exiting streaming
mode in the hardware would do so that if that state is reloaded we get the
same behaviour. Without this we will reload whatever the last FPSIMD state
that was saved for the task was.
Fixes: 40a8e87bb3285 ("arm64/sme: Disable ZA and streaming mode when handling signals")
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kernel/signal.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 13dee9cedfc6..51fb4268f0ed 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -922,6 +922,16 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
/* Signal handlers are invoked with ZA and streaming mode disabled */
if (system_supports_sme()) {
+ /*
+ * If we were in streaming mode the saved register
+ * state was SVE but we will exit SM and use the
+ * FPSIMD register state - flush the saved FPSIMD
+ * register state in case it gets loaded.
+ */
+ if (current->thread.svcr & SVCR_SM_MASK)
+ memset(¤t->thread.uw.fpsimd_state, 0,
+ sizeof(current->thread.uw.fpsimd_state));
+
current->thread.svcr &= ~(SVCR_ZA_MASK |
SVCR_SM_MASK);
sme_smstop();
--
2.30.2
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v1 3/4] arm64/sme: Don't flush SVE register state when allocating SME storage
2022-08-11 10:57 [PATCH v1 0/4] arm64/sme: SME related fixes Mark Brown
2022-08-11 10:57 ` [PATCH v1 1/4] arm64/signal: Raise limit on stack frames Mark Brown
2022-08-11 10:57 ` [PATCH v1 2/4] arm64/signal: Flush FPSIMD register state when disabling streaming mode Mark Brown
@ 2022-08-11 10:57 ` Mark Brown
2022-08-11 10:57 ` [PATCH v1 4/4] arm64/sme: Don't flush SVE register state when handling SME traps Mark Brown
3 siblings, 0 replies; 5+ messages in thread
From: Mark Brown @ 2022-08-11 10:57 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon; +Cc: linux-arm-kernel, Mark Brown
Currently when taking a SME access trap we allocate storage for the SVE
register state in order to be able to handle storage of streaming mode SVE.
Due to the original usage in a purely SVE context the SVE register state
allocation this also flushes the register state for SVE if storage was
already allocated but in the SME context this is not desirable. For a SME
access trap to be taken the task must not be in streaming mode so either
there already is SVE register state present for regular SVE mode which would
be corrupted or the task does not have TIF_SVE and the flush is redundant.
Fix this by adding a flag to sve_alloc() indicating if we are in a SVE
context and need to flush the state. Freshly allocated storage is always
zeroed either way.
Fixes: 8bd7f91c03d88 ("arm64/sme: Implement traps and syscall handling for SME")
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/fpsimd.h | 2 +-
arch/arm64/kernel/fpsimd.c | 10 ++++++----
arch/arm64/kernel/ptrace.c | 6 +++---
arch/arm64/kernel/signal.c | 2 +-
4 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 9bb1873f5295..d820f55e8a17 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -153,7 +153,7 @@ struct vl_info {
#ifdef CONFIG_ARM64_SVE
-extern void sve_alloc(struct task_struct *task);
+extern void sve_alloc(struct task_struct *task, bool flush);
extern void fpsimd_release_task(struct task_struct *task);
extern void fpsimd_sync_to_sve(struct task_struct *task);
extern void fpsimd_force_sync_to_sve(struct task_struct *task);
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index aecf3071efdd..763a4ab557ec 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -716,10 +716,12 @@ size_t sve_state_size(struct task_struct const *task)
* do_sve_acc() case, there is no ABI requirement to hide stale data
* written previously be task.
*/
-void sve_alloc(struct task_struct *task)
+void sve_alloc(struct task_struct *task, bool flush)
{
if (task->thread.sve_state) {
- memset(task->thread.sve_state, 0, sve_state_size(task));
+ if (flush)
+ memset(task->thread.sve_state, 0,
+ sve_state_size(task));
return;
}
@@ -1389,7 +1391,7 @@ void do_sve_acc(unsigned long esr, struct pt_regs *regs)
return;
}
- sve_alloc(current);
+ sve_alloc(current, true);
if (!current->thread.sve_state) {
force_sig(SIGKILL);
return;
@@ -1440,7 +1442,7 @@ void do_sme_acc(unsigned long esr, struct pt_regs *regs)
return;
}
- sve_alloc(current);
+ sve_alloc(current, false);
sme_alloc(current);
if (!current->thread.sve_state || !current->thread.za_state) {
force_sig(SIGKILL);
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 21da83187a60..eb7c08dfb834 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -882,7 +882,7 @@ static int sve_set_common(struct task_struct *target,
* state and ensure there's storage.
*/
if (target->thread.svcr != old_svcr)
- sve_alloc(target);
+ sve_alloc(target, true);
}
/* Registers: FPSIMD-only case */
@@ -912,7 +912,7 @@ static int sve_set_common(struct task_struct *target,
goto out;
}
- sve_alloc(target);
+ sve_alloc(target, true);
if (!target->thread.sve_state) {
ret = -ENOMEM;
clear_tsk_thread_flag(target, TIF_SVE);
@@ -1082,7 +1082,7 @@ static int za_set(struct task_struct *target,
/* Ensure there is some SVE storage for streaming mode */
if (!target->thread.sve_state) {
- sve_alloc(target);
+ sve_alloc(target, false);
if (!target->thread.sve_state) {
clear_thread_flag(TIF_SME);
ret = -ENOMEM;
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 51fb4268f0ed..e4de799da500 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -307,7 +307,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
fpsimd_flush_task_state(current);
/* From now, fpsimd_thread_switch() won't touch thread.sve_state */
- sve_alloc(current);
+ sve_alloc(current, true);
if (!current->thread.sve_state) {
clear_thread_flag(TIF_SVE);
return -ENOMEM;
--
2.30.2
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v1 4/4] arm64/sme: Don't flush SVE register state when handling SME traps
2022-08-11 10:57 [PATCH v1 0/4] arm64/sme: SME related fixes Mark Brown
` (2 preceding siblings ...)
2022-08-11 10:57 ` [PATCH v1 3/4] arm64/sme: Don't flush SVE register state when allocating SME storage Mark Brown
@ 2022-08-11 10:57 ` Mark Brown
3 siblings, 0 replies; 5+ messages in thread
From: Mark Brown @ 2022-08-11 10:57 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon; +Cc: linux-arm-kernel, Mark Brown
Currently as part of handling a SME access trap we flush the SVE register
state. This is not needed and would corrupt register state if the task has
access to the SVE registers already. For non-streaming mode accesses the
required flushing will be done in the SVE access trap. For streaming
mode SVE register accesses the architecture guarantees that the register
state will be flushed when streaming mode is entered or exited so there is
no need for us to do so. Simply remove the register initialisation.
Fixes: 8bd7f91c03d88 ("arm64/sme: Implement traps and syscall handling for SME")
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kernel/fpsimd.c | 11 -----------
1 file changed, 11 deletions(-)
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 763a4ab557ec..52f7ffdffbcb 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1463,17 +1463,6 @@ void do_sme_acc(unsigned long esr, struct pt_regs *regs)
fpsimd_bind_task_to_cpu();
}
- /*
- * If SVE was not already active initialise the SVE registers,
- * any non-shared state between the streaming and regular SVE
- * registers is architecturally guaranteed to be zeroed when
- * we enter streaming mode. We do not need to initialize ZA
- * since ZA must be disabled at this point and enabling ZA is
- * architecturally defined to zero ZA.
- */
- if (system_supports_sve() && !test_thread_flag(TIF_SVE))
- sve_init_regs();
-
put_cpu_fpsimd_context();
}
--
2.30.2
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2022-08-11 10:57 [PATCH v1 0/4] arm64/sme: SME related fixes Mark Brown
2022-08-11 10:57 ` [PATCH v1 1/4] arm64/signal: Raise limit on stack frames Mark Brown
2022-08-11 10:57 ` [PATCH v1 2/4] arm64/signal: Flush FPSIMD register state when disabling streaming mode Mark Brown
2022-08-11 10:57 ` [PATCH v1 3/4] arm64/sme: Don't flush SVE register state when allocating SME storage Mark Brown
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