linux-kernel - [PATCH V2] arm64/mm: Stop using ESR_ELx_FSC

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Date: Tue, 18 Jun 2024 09:17:03 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: mark.rutland@....com,
	ryan.roberts@....com,
	maz@...nel.org,
	Anshuman Khandual <anshuman.khandual@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH V2] arm64/mm: Stop using ESR_ELx_FSC_TYPE during fault

Fault status codes at page table level 0, 1, 2 and 3 for access, permission
and translation faults are architecturally organized in a way, that masking
out ESR_ELx_FSC_TYPE, fetches Level 0 status code for the respective fault.

Helpers like esr_fsc_is_[translation|permission|access_flag]_fault() mask
out ESR_ELx_FSC_TYPE before comparing against corresponding Level 0 status
code as the kernel does not yet care about the page table level, where in
the fault really occurred previously.

This scheme is starting to crumble after FEAT_LPA2 when level -1 got added.
Fault status code for translation fault at level -1 is 0x2B which does not
follow ESR_ELx_FSC_TYPE, requiring esr_fsc_is_translation_fault() changes.

This changes above helpers to compare against individual fault status code
values for each page table level and stop using ESR_ELx_FSC_TYPE, which is
losing its value as a common mask.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
This applies on v6.10-rc4 and still leaves behind ESR_ELx_FSC_TYPE for now.

Changes in V2:

- Defined ESR_ELx_FSC_[ACCESS|FAULT_PERM]_L() macros
- Changed fault helpers using the above macros instead
- Dropped each page table level fault status discrete values
- Dropped set_thread_esr() changes in arch/arm64/mm/fault.c
- Updated the commit message

Changes in V1:

https://lore.kernel.org/linux-arm-kernel/20240613094538.3263536-1-anshuman.khandual@arm.com/

 arch/arm64/include/asm/esr.h | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 7abf09df7033..3f482500f71f 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -121,6 +121,14 @@
 #define ESR_ELx_FSC_SECC	(0x18)
 #define ESR_ELx_FSC_SECC_TTW(n)	(0x1c + (n))
 
+/* Status codes for individual page table levels */
+#define ESR_ELx_FSC_ACCESS_L(n)	(ESR_ELx_FSC_ACCESS + n)
+#define ESR_ELx_FSC_PERM_L(n)	(ESR_ELx_FSC_PERM + n)
+
+#define ESR_ELx_FSC_FAULT_nL	(0x2C)
+#define ESR_ELx_FSC_FAULT_L(n)	(((n) < 0 ? ESR_ELx_FSC_FAULT_nL : \
+					    ESR_ELx_FSC_FAULT) + (n))
+
 /* ISS field definitions for Data Aborts */
 #define ESR_ELx_ISV_SHIFT	(24)
 #define ESR_ELx_ISV		(UL(1) << ESR_ELx_ISV_SHIFT)
@@ -388,20 +396,33 @@ static inline bool esr_is_data_abort(unsigned long esr)
 
 static inline bool esr_fsc_is_translation_fault(unsigned long esr)
 {
-	/* Translation fault, level -1 */
-	if ((esr & ESR_ELx_FSC) == 0b101011)
-		return true;
-	return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_FAULT;
+	esr = esr & ESR_ELx_FSC;
+
+	return (esr == ESR_ELx_FSC_FAULT_L(3)) ||
+	       (esr == ESR_ELx_FSC_FAULT_L(2)) ||
+	       (esr == ESR_ELx_FSC_FAULT_L(1)) ||
+	       (esr == ESR_ELx_FSC_FAULT_L(0)) ||
+	       (esr == ESR_ELx_FSC_FAULT_L(-1));
 }
 
 static inline bool esr_fsc_is_permission_fault(unsigned long esr)
 {
-	return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_PERM;
+	esr = esr & ESR_ELx_FSC;
+
+	return (esr == ESR_ELx_FSC_PERM_L(3)) ||
+	       (esr == ESR_ELx_FSC_PERM_L(2)) ||
+	       (esr == ESR_ELx_FSC_PERM_L(1)) ||
+	       (esr == ESR_ELx_FSC_PERM_L(0));
 }
 
 static inline bool esr_fsc_is_access_flag_fault(unsigned long esr)
 {
-	return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_ACCESS;
+	esr = esr & ESR_ELx_FSC;
+
+	return (esr == ESR_ELx_FSC_ACCESS_L(3)) ||
+	       (esr == ESR_ELx_FSC_ACCESS_L(2)) ||
+	       (esr == ESR_ELx_FSC_ACCESS_L(1)) ||
+	       (esr == ESR_ELx_FSC_ACCESS_L(0));
 }
 
 /* Indicate whether ESR.EC==0x1A is for an ERETAx instruction */
-- 
2.30.2