On Thu, 30 Sep 2021 19:11:29 +0100 Mark Brown broonie@kernel.org wrote:
Allocate space for storing ZA on first access to SME and use that to save and restore ZA state when context switching. We do this by using the vector form of the LDR and STR ZA instructions, these do not require streaming mode and have implementation recommendations that they avoid contention issues in shared SMCU implementations.
Since ZA is architecturally guaranteed to be zeroed when enabled we do not need to explicitly zero ZA, either we will be restoring from a saved copy or trapping on first use of SME so we know that ZA must be disabled.
Signed-off-by: Mark Brown broonie@kernel.org
sme_alloc() forwards definition should be in the next patch.
arch/arm64/include/asm/fpsimd.h | 5 ++++- arch/arm64/include/asm/fpsimdmacros.h | 22 ++++++++++++++++++++++ arch/arm64/include/asm/processor.h | 1 + arch/arm64/kernel/entry-fpsimd.S | 22 ++++++++++++++++++++++ arch/arm64/kernel/fpsimd.c | 16 ++++++++++------ arch/arm64/kvm/fpsimd.c | 2 +- 6 files changed, 60 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index 43737ca91f1a..45f7153067bb 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -47,7 +47,7 @@ extern void fpsimd_update_current_state(struct user_fpsimd_state const *state); extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state, void *sve_state, unsigned int sve_vl,
unsigned int sme_vl);
void *za_state, unsigned int sme_vl);extern void fpsimd_flush_task_state(struct task_struct *target); extern void fpsimd_save_and_flush_cpu_state(void); @@ -90,6 +90,8 @@ extern void sve_flush_live(bool flush_ffr, unsigned long vq_minus_1); extern unsigned int sve_get_vl(void); extern void sve_set_vq(unsigned long vq_minus_1); extern void sme_set_vq(unsigned long vq_minus_1); +extern void sme_save_state(void *state, unsigned int vq_minus_1); +extern void sme_load_state(void const *state, unsigned int vq_minus_1); struct arm64_cpu_capabilities; extern void sve_kernel_enable(const struct arm64_cpu_capabilities *__unused); @@ -119,6 +121,7 @@ static inline unsigned int __bit_to_vq(unsigned int bit) extern size_t sve_state_size(struct task_struct const *task); extern void sve_alloc(struct task_struct *task); +extern void sme_alloc(struct task_struct *task);
Should be in the next patch where this function is introduced.
extern void fpsimd_release_task(struct task_struct *task); extern void fpsimd_sync_to_sve(struct task_struct *task); extern void sve_sync_to_fpsimd(struct task_struct *task);