TCR2_ELx.E0POE is set during smp_init(). However, this bit is not reprogrammed when the CPU enters suspension and later resumes via cpu_resume(), as __cpu_setup() does not re-enable E0POE and there is no save/restore logic for the TCR2_ELx system register.
As a result, the E0POE feature no longer works after cpu_resume().
To address this, save and restore TCR2_EL1 in the cpu_suspend()/cpu_resume() path, rather than adding related logic to __cpu_setup(), taking into account possible future extensions of the TCR2_ELx feature.
Cc: stable@vger.kernel.org Fixes: bf83dae90fbc ("arm64: enable the Permission Overlay Extension for EL0") Signed-off-by: Yeoreum Yun yeoreum.yun@arm.com ---
Patch History ============== from v1 to v2: - following @Kevin Brodsky suggestion. - https://lore.kernel.org/all/20260105200707.2071169-1-yeoreum.yun@arm.com/
NOTE: This patch based on v6.19-rc4 --- arch/arm64/include/asm/suspend.h | 2 +- arch/arm64/mm/proc.S | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/suspend.h b/arch/arm64/include/asm/suspend.h index e65f33edf9d6..e9ce68d50ba4 100644 --- a/arch/arm64/include/asm/suspend.h +++ b/arch/arm64/include/asm/suspend.h @@ -2,7 +2,7 @@ #ifndef __ASM_SUSPEND_H #define __ASM_SUSPEND_H
-#define NR_CTX_REGS 13 +#define NR_CTX_REGS 14 #define NR_CALLEE_SAVED_REGS 12
/* diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 01e868116448..5d907ce3b6d3 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -110,6 +110,10 @@ SYM_FUNC_START(cpu_do_suspend) * call stack. */ str x18, [x0, #96] +alternative_if ARM64_HAS_TCR2 + mrs x2, REG_TCR2_EL1 + str x2, [x0, #104] +alternative_else_nop_endif ret SYM_FUNC_END(cpu_do_suspend)
@@ -144,6 +148,10 @@ SYM_FUNC_START(cpu_do_resume) msr tcr_el1, x8 msr vbar_el1, x9 msr mdscr_el1, x10 +alternative_if ARM64_HAS_TCR2 + ldr x2, [x0, #104] + msr REG_TCR2_EL1, x2 +alternative_else_nop_endif
msr sctlr_el1, x12 set_this_cpu_offset x13 -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
On 07/01/2026 17:21, Yeoreum Yun wrote:
TCR2_ELx.E0POE is set during smp_init(). However, this bit is not reprogrammed when the CPU enters suspension and later resumes via cpu_resume(), as __cpu_setup() does not re-enable E0POE and there is no save/restore logic for the TCR2_ELx system register.
As a result, the E0POE feature no longer works after cpu_resume().
To address this, save and restore TCR2_EL1 in the cpu_suspend()/cpu_resume() path, rather than adding related logic to __cpu_setup(), taking into account possible future extensions of the TCR2_ELx feature.
Cc: stable@vger.kernel.org Fixes: bf83dae90fbc ("arm64: enable the Permission Overlay Extension for EL0") Signed-off-by: Yeoreum Yun yeoreum.yun@arm.com
Patch History
from v1 to v2:
- following @Kevin Brodsky suggestion.
- https://lore.kernel.org/all/20260105200707.2071169-1-yeoreum.yun@arm.com/
NOTE: This patch based on v6.19-rc4
arch/arm64/include/asm/suspend.h | 2 +- arch/arm64/mm/proc.S | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/suspend.h b/arch/arm64/include/asm/suspend.h index e65f33edf9d6..e9ce68d50ba4 100644 --- a/arch/arm64/include/asm/suspend.h +++ b/arch/arm64/include/asm/suspend.h @@ -2,7 +2,7 @@ #ifndef __ASM_SUSPEND_H #define __ASM_SUSPEND_H
-#define NR_CTX_REGS 13 +#define NR_CTX_REGS 14 #define NR_CALLEE_SAVED_REGS 12
/* diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 01e868116448..5d907ce3b6d3 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -110,6 +110,10 @@ SYM_FUNC_START(cpu_do_suspend) * call stack. */ str x18, [x0, #96] +alternative_if ARM64_HAS_TCR2
- mrs x2, REG_TCR2_EL1
- str x2, [x0, #104]
+alternative_else_nop_endif ret SYM_FUNC_END(cpu_do_suspend)
@@ -144,6 +148,10 @@ SYM_FUNC_START(cpu_do_resume) msr tcr_el1, x8 msr vbar_el1, x9 msr mdscr_el1, x10 +alternative_if ARM64_HAS_TCR2
- ldr x2, [x0, #104]
- msr REG_TCR2_EL1, x2
+alternative_else_nop_endif
Maybe this could be pushed further down cpu_do_resume, next to DISR_EL1 maybe (since it's also conditional)? Otherwise the diff LGTM:
Reviewed-by: Kevin Brodsky kevin.brodsky@arm.com
- Kevin
msr sctlr_el1, x12 set_this_cpu_offset x13 -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
Hi Kevin,
[...]
@@ -144,6 +148,10 @@ SYM_FUNC_START(cpu_do_resume) msr tcr_el1, x8 msr vbar_el1, x9 msr mdscr_el1, x10 +alternative_if ARM64_HAS_TCR2
- ldr x2, [x0, #104]
- msr REG_TCR2_EL1, x2
+alternative_else_nop_endif
Maybe this could be pushed further down cpu_do_resume, next to DISR_EL1 maybe (since it's also conditional)? Otherwise the diff LGTM:
Sorry but IIUC, currently there is no DISR_EL1 save/restore not yet? and I think current place is good where before restore SCTLR_EL1 which before MMU enabled.
Am I missing something?
Thanks.
-- Sincerely, Yeoreum Yun
On 07/01/26 9:51 PM, Yeoreum Yun wrote:
TCR2_ELx.E0POE is set during smp_init(). However, this bit is not reprogrammed when the CPU enters suspension and later resumes via cpu_resume(), as __cpu_setup() does not re-enable E0POE and there is no save/restore logic for the TCR2_ELx system register.
As a result, the E0POE feature no longer works after cpu_resume().
To address this, save and restore TCR2_EL1 in the cpu_suspend()/cpu_resume() path, rather than adding related logic to __cpu_setup(), taking into account possible future extensions of the TCR2_ELx feature.
Cc: stable@vger.kernel.org Fixes: bf83dae90fbc ("arm64: enable the Permission Overlay Extension for EL0") Signed-off-by: Yeoreum Yun yeoreum.yun@arm.com
Patch History
from v1 to v2:
- following @Kevin Brodsky suggestion.
- https://lore.kernel.org/all/20260105200707.2071169-1-yeoreum.yun@arm.com/
NOTE: This patch based on v6.19-rc4
arch/arm64/include/asm/suspend.h | 2 +- arch/arm64/mm/proc.S | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/suspend.h b/arch/arm64/include/asm/suspend.h index e65f33edf9d6..e9ce68d50ba4 100644 --- a/arch/arm64/include/asm/suspend.h +++ b/arch/arm64/include/asm/suspend.h @@ -2,7 +2,7 @@ #ifndef __ASM_SUSPEND_H #define __ASM_SUSPEND_H
-#define NR_CTX_REGS 13 +#define NR_CTX_REGS 14 #define NR_CALLEE_SAVED_REGS 12
/* diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 01e868116448..5d907ce3b6d3 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -110,6 +110,10 @@ SYM_FUNC_START(cpu_do_suspend) * call stack. */ str x18, [x0, #96] +alternative_if ARM64_HAS_TCR2
- mrs x2, REG_TCR2_EL1
- str x2, [x0, #104]
+alternative_else_nop_endif ret SYM_FUNC_END(cpu_do_suspend)
@@ -144,6 +148,10 @@ SYM_FUNC_START(cpu_do_resume) msr tcr_el1, x8 msr vbar_el1, x9 msr mdscr_el1, x10 +alternative_if ARM64_HAS_TCR2
- ldr x2, [x0, #104]
- msr REG_TCR2_EL1, x2
+alternative_else_nop_endif
msr sctlr_el1, x12 set_this_cpu_offset x13 -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
LGTM
Reviewed-by: Anshuman Khandual anshuman.khandual@arm.com
On Wed, 07 Jan 2026 16:21:15 +0000, Yeoreum Yun wrote:
TCR2_ELx.E0POE is set during smp_init(). However, this bit is not reprogrammed when the CPU enters suspension and later resumes via cpu_resume(), as __cpu_setup() does not re-enable E0POE and there is no save/restore logic for the TCR2_ELx system register.
As a result, the E0POE feature no longer works after cpu_resume().
[...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arm64: fix cleared E0POE bit after cpu_suspend()/resume() https://git.kernel.org/arm64/c/bdf3f4176092
linux-stable-mirror@lists.linaro.org
-
Anshuman Khandual -
Catalin Marinas -
Kevin Brodsky -
Yeoreum Yun