This is a note to let you know that I've just added the patch titled
RISC-V: Enable cbo.zero in usermode
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
risc-v-enable-cbo.zero-in-usermode.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 225e330455f209634733314a13070234294a4e02
Author: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
Date: Mon Sep 18 15:15:21 2023 +0200
RISC-V: Enable cbo.zero in usermode
[ Upstream commit 43c16d51a19b0ba2ed66978d5924d486ec1e42bc ]
When Zicboz is present, enable its instruction (cbo.zero) in
usermode by setting its respective senvcfg bit. We don't bother
trying to set this bit per-task, which would also require an
interface for tasks to request enabling and/or disabling. Instead,
permanently set the bit for each hart which has the extension when
bringing it online.
This patch also introduces riscv_cpu_has_extension_[un]likely()
functions to check a specific hart's ISA bitmap for extensions.
Prior to checking the specific hart's bitmap in these functions
we try the bitmap which represents the LCD of extensions, but only
when we know it will use its optimized, alternatives path by gating
its call on CONFIG_RISCV_ALTERNATIVE. When alternatives are used, the
compiler ensures that the invocation of the LCD search becomes a
constant true or false. When it's true, even the new functions will
completely vanish from their callsites. OTOH, when the LCD check is
false, we need to do a search of the hart's ISA bitmap. Had we also
checked the LCD bitmap without the use of alternatives, then we would
have ended up with two bitmap searches instead of one.
Signed-off-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230918131518.56803-10-ajones@xxxxxxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Stable-dep-of: 58661a30f1bc ("riscv: Flush the instruction cache during SMP bringup")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index d0345bd659c94..13b7d35648a9c 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -31,5 +31,6 @@ DECLARE_PER_CPU(long, misaligned_access_speed);
extern struct riscv_isainfo hart_isa[NR_CPUS];
void check_unaligned_access(int cpu);
+void riscv_user_isa_enable(void);
#endif
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 777cb8299551c..5fba25db82d2a 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -275,6 +275,7 @@
#define CSR_SIE 0x104
#define CSR_STVEC 0x105
#define CSR_SCOUNTEREN 0x106
+#define CSR_SENVCFG 0x10a
#define CSR_SSCRATCH 0x140
#define CSR_SEPC 0x141
#define CSR_SCAUSE 0x142
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index f4157034efa9c..e215d3399a179 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -70,6 +70,7 @@
#ifndef __ASSEMBLY__
#include <linux/jump_label.h>
+#include <asm/cpufeature.h>
unsigned long riscv_get_elf_hwcap(void);
@@ -137,6 +138,21 @@ riscv_has_extension_unlikely(const unsigned long ext)
return true;
}
+static __always_inline bool riscv_cpu_has_extension_likely(int cpu, const unsigned long ext)
+{
+ if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_likely(ext))
+ return true;
+
+ return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
+}
+
+static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsigned long ext)
+{
+ if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_unlikely(ext))
+ return true;
+
+ return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
+}
#endif
#endif /* _ASM_RISCV_HWCAP_H */
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index e39a905aca248..6754a922a844f 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -672,6 +672,12 @@ static int check_unaligned_access_boot_cpu(void)
arch_initcall(check_unaligned_access_boot_cpu);
+void riscv_user_isa_enable(void)
+{
+ if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_ZICBOZ))
+ csr_set(CSR_SENVCFG, ENVCFG_CBZE);
+}
+
#ifdef CONFIG_RISCV_ALTERNATIVE
/*
* Alternative patch sites consider 48 bits when determining when to patch
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index e600aab116a40..8fd6c02353d43 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -26,6 +26,7 @@
#include <asm/acpi.h>
#include <asm/alternative.h>
#include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
#include <asm/cpu_ops.h>
#include <asm/early_ioremap.h>
#include <asm/pgtable.h>
@@ -314,10 +315,13 @@ void __init setup_arch(char **cmdline_p)
riscv_fill_hwcap();
init_rt_signal_env();
apply_boot_alternatives();
+
if (IS_ENABLED(CONFIG_RISCV_ISA_ZICBOM) &&
riscv_isa_extension_available(NULL, ZICBOM))
riscv_noncoherent_supported();
riscv_set_dma_cache_alignment();
+
+ riscv_user_isa_enable();
}
static int __init topology_init(void)
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 1b8da4e40a4d6..d1b0a6fc3adfc 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -25,6 +25,8 @@
#include <linux/of.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/mm.h>
+
+#include <asm/cpufeature.h>
#include <asm/cpu_ops.h>
#include <asm/cpufeature.h>
#include <asm/irq.h>
@@ -253,6 +255,8 @@ asmlinkage __visible void smp_callin(void)
elf_hwcap &= ~COMPAT_HWCAP_ISA_V;
}
+ riscv_user_isa_enable();
+
/*
* Remote TLB flushes are ignored while the CPU is offline, so emit
* a local TLB flush right now just in case.
