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riscv: uaccess: Only restore the CSR_STATUS SUM bit

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During switch to csrs will OR the value of the register into the
corresponding csr. In this case we're only interested in restoring the
SUM bit not the entire register.

Signed-off-by: Cyril Bur <cyrilbur@tenstorrent.com>
Link: https://lore.kernel.org/r/20250522160954.429333-1-cyrilbur@tenstorrent.com
Co-developed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Fixes: 788aa64c01 ("riscv: save the SR_SUM status over switches")
Link: https://lore.kernel.org/r/20250602121543.1544278-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
This commit is contained in:
Cyril Bur 2025-06-02 12:15:43 +00:00 committed by Palmer Dabbelt
parent 2670a39b1e
commit 265d6aba16
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GPG Key ID: 2E1319F35FBB1889
3 changed files with 9 additions and 8 deletions
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2
arch/riscv/include/asm/processor.h
View File

@ -110,7 +110,7 @@ struct thread_struct {
struct __riscv_d_ext_state fstate;
unsigned long bad_cause;
unsigned long envcfg;
unsigned long status;
unsigned long sum;
u32 riscv_v_flags;
u32 vstate_ctrl;
struct __riscv_v_ext_state vstate;

6
arch/riscv/kernel/asm-offsets.c
View File

@ -34,7 +34,7 @@ void asm_offsets(void)
OFFSET(TASK_THREAD_S9, task_struct, thread.s[9]);
OFFSET(TASK_THREAD_S10, task_struct, thread.s[10]);
OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]);
OFFSET(TASK_THREAD_STATUS, task_struct, thread.status);
OFFSET(TASK_THREAD_SUM, task_struct, thread.sum);
OFFSET(TASK_TI_CPU, task_struct, thread_info.cpu);
OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count);
@ -347,8 +347,8 @@ void asm_offsets(void)
offsetof(struct task_struct, thread.s[11])
- offsetof(struct task_struct, thread.ra)
);
DEFINE(TASK_THREAD_STATUS_RA,
offsetof(struct task_struct, thread.status)
DEFINE(TASK_THREAD_SUM_RA,
offsetof(struct task_struct, thread.sum)
- offsetof(struct task_struct, thread.ra)
);

9
arch/riscv/kernel/entry.S
View File

@ -399,14 +399,15 @@ SYM_FUNC_START(__switch_to)
REG_S s11, TASK_THREAD_S11_RA(a3)
/* save the user space access flag */
li s0, SR_SUM
csrr s1, CSR_STATUS
REG_S s1, TASK_THREAD_STATUS_RA(a3)
csrr s0, CSR_STATUS
REG_S s0, TASK_THREAD_SUM_RA(a3)
/* Save the kernel shadow call stack pointer */
scs_save_current
/* Restore context from next->thread */
REG_L s0, TASK_THREAD_STATUS_RA(a4)
REG_L s0, TASK_THREAD_SUM_RA(a4)
li s1, SR_SUM
and s0, s0, s1
csrs CSR_STATUS, s0
REG_L ra, TASK_THREAD_RA_RA(a4)
REG_L sp, TASK_THREAD_SP_RA(a4)