linux-kernel - [PATCH -fixes v4 3/3] riscv: Save/restore envcfg CSR during CPU suspend

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Date: Tue, 27 Feb 2024 22:55:35 -0800
From: Samuel Holland <samuel.holland@...ive.com>
To: Palmer Dabbelt <palmer@...belt.com>
Cc: Andrew Jones <ajones@...tanamicro.com>,
	linux-kernel@...r.kernel.org,
	Conor Dooley <conor@...nel.org>,
	Alexandre Ghiti <alex@...ti.fr>,
	linux-riscv@...ts.infradead.org,
	Stefan O'Rear <sorear@...tmail.com>,
	Samuel Holland <samuel.holland@...ive.com>,
	stable@...r.kernel.org
Subject: [PATCH -fixes v4 3/3] riscv: Save/restore envcfg CSR during CPU suspend

The value of the [ms]envcfg CSR is lost when entering a nonretentive
idle state, so the CSR must be rewritten when resuming the CPU.

Cc: <stable@...r.kernel.org> # v6.7+
Fixes: 43c16d51a19b ("RISC-V: Enable cbo.zero in usermode")
Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
---

Changes in v4:
 - Check for Xlinuxenvcfg instead of Zicboz

Changes in v3:
 - Check for Zicboz instead of the privileged ISA version

Changes in v2:
 - Check for privileged ISA v1.12 instead of the specific CSR
 - Use riscv_has_extension_likely() instead of new ALTERNATIVE()s

 arch/riscv/include/asm/suspend.h | 1 +
 arch/riscv/kernel/suspend.c      | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h
index 02f87867389a..491296a335d0 100644
--- a/arch/riscv/include/asm/suspend.h
+++ b/arch/riscv/include/asm/suspend.h
@@ -14,6 +14,7 @@ struct suspend_context {
 	struct pt_regs regs;
 	/* Saved and restored by high-level functions */
 	unsigned long scratch;
+	unsigned long envcfg;
 	unsigned long tvec;
 	unsigned long ie;
 #ifdef CONFIG_MMU
diff --git a/arch/riscv/kernel/suspend.c b/arch/riscv/kernel/suspend.c
index 239509367e42..299795341e8a 100644
--- a/arch/riscv/kernel/suspend.c
+++ b/arch/riscv/kernel/suspend.c
@@ -15,6 +15,8 @@
 void suspend_save_csrs(struct suspend_context *context)
 {
 	context->scratch = csr_read(CSR_SCRATCH);
+	if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))
+		context->envcfg = csr_read(CSR_ENVCFG);
 	context->tvec = csr_read(CSR_TVEC);
 	context->ie = csr_read(CSR_IE);
 
@@ -36,6 +38,8 @@ void suspend_save_csrs(struct suspend_context *context)
 void suspend_restore_csrs(struct suspend_context *context)
 {
 	csr_write(CSR_SCRATCH, context->scratch);
+	if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))
+		csr_write(CSR_ENVCFG, context->envcfg);
 	csr_write(CSR_TVEC, context->tvec);
 	csr_write(CSR_IE, context->ie);
 
-- 
2.43.1