arm64/sme: Don't flush SVE register state when allocating SME storage

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: 8bd7f91c03d8 ("arm64/sme: Implement traps and syscall handling for SME")
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220817182324.638214-4-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 9bb1873f529515a9ec9e1ee487a4e9e8a02e1f3b..6f86b7ab6c28f00d38573336c9e0425df75d80c1 100644 (file)
--- 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);
@@ -256,7 +256,7 @@ size_t sve_state_size(struct task_struct const *task);
 
 #else /* ! CONFIG_ARM64_SVE */
 
-static inline void sve_alloc(struct task_struct *task) { }
+static inline void sve_alloc(struct task_struct *task, bool flush) { }
 static inline void fpsimd_release_task(struct task_struct *task) { }
 static inline void sve_sync_to_fpsimd(struct task_struct *task) { }
 static inline void sve_sync_from_fpsimd_zeropad(struct task_struct *task) { }

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index dd63ffc3a2fa2782823fec804c8327405c69a4cd..b9ae9827e6e8eb818f625b1f6e41d8b4f38f4e43 100644 (file)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -715,10 +715,12 @@ 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;
        }
 
@@ -1388,7 +1390,7 @@ 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;
@@ -1439,7 +1441,7 @@ 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 21da83187a602c499e4240d538d28da3bed5624d..eb7c08dfb8348e29175e0076eb5c783bea24f8d3 100644 (file)
--- 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 0d28a783a69a1c28a598bdf7ef0bc583bdc70fa2..9ad911f1647c8a204424b992255f11de92279332 100644 (file)
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -310,7 +310,7 @@ 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;