[PATCH v2 03/12] powerpc/dexcr: Add initial Dynamic Execution Control Register (DEXCR) support
Benjamin Gray
bgray at linux.ibm.com
Thu Mar 30 16:50:31 AEDT 2023
ISA 3.1B introduces the Dynamic Execution Control Register (DEXCR). It
is a per-cpu register that allows control over various CPU behaviours
including branch hint usage, indirect branch speculation, and
hashst/hashchk support.
Add some definitions and basic support for the DEXCR in the kernel.
Right now it just
* Zero initialises the DEXCR and HASHKEYR when a CPU onlines.
* Clears them in reset_sprs().
* Detects when the NPHIE aspect is supported (the others don't get
looked at in this series, so there's no need to waste a CPU_FTR
on them).
We initialise the HASHKEYR to ensure that all cores have the same key,
so an HV enforced NPHIE + swapping cores doesn't randomly crash a
process using hash instructions. The stores to HASHKEYR are
unconditional because the ISA makes no mention of the SPR being missing
if support for doing the hashes isn't present. So all that would happen
is the HASHKEYR value gets ignored. This helps slightly if NPHIE
detection fails; e.g., we currently only detect it on pseries.
Signed-off-by: Benjamin Gray <bgray at linux.ibm.com>
---
v2: * More definitions for ptrace
v1: * Only make a CPU feature for NPHIE. We only need to know if the
hashst/hashchk functionality is supported for a static DEXCR.
* Initialise the DEXCR to 0 when each CPU comes online. Remove
the dexcr_init() and get_thread_dexcr() functions.
* No longer track the DEXCR in a per-thread field.
* Remove the made-up Opal features
---
arch/powerpc/include/asm/book3s/64/kexec.h | 5 +++++
arch/powerpc/include/asm/cputable.h | 4 +++-
arch/powerpc/include/asm/reg.h | 10 ++++++++++
arch/powerpc/kernel/cpu_setup_power.c | 8 ++++++++
arch/powerpc/kernel/prom.c | 1 +
5 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/book3s/64/kexec.h b/arch/powerpc/include/asm/book3s/64/kexec.h
index d4b9d476ecba..df37a76c1e9f 100644
--- a/arch/powerpc/include/asm/book3s/64/kexec.h
+++ b/arch/powerpc/include/asm/book3s/64/kexec.h
@@ -21,6 +21,11 @@ static inline void reset_sprs(void)
plpar_set_ciabr(0);
}
+ if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+ mtspr(SPRN_DEXCR, 0);
+ mtspr(SPRN_HASHKEYR, 0);
+ }
+
/* Do we need isync()? We are going via a kexec reset */
isync();
}
diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index 757dbded11dc..443a9d482b15 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -192,6 +192,7 @@ static inline void cpu_feature_keys_init(void) { }
#define CPU_FTR_P9_RADIX_PREFETCH_BUG LONG_ASM_CONST(0x0002000000000000)
#define CPU_FTR_ARCH_31 LONG_ASM_CONST(0x0004000000000000)
#define CPU_FTR_DAWR1 LONG_ASM_CONST(0x0008000000000000)
+#define CPU_FTR_DEXCR_NPHIE LONG_ASM_CONST(0x0010000000000000)
#ifndef __ASSEMBLY__
@@ -451,7 +452,8 @@ static inline void cpu_feature_keys_init(void) { }
CPU_FTR_CFAR | CPU_FTR_HVMODE | CPU_FTR_VMX_COPY | \
CPU_FTR_DBELL | CPU_FTR_HAS_PPR | CPU_FTR_ARCH_207S | \
CPU_FTR_ARCH_300 | CPU_FTR_ARCH_31 | \
- CPU_FTR_DAWR | CPU_FTR_DAWR1)
+ CPU_FTR_DAWR | CPU_FTR_DAWR1 | \
+ CPU_FTR_DEXCR_NPHIE)
#define CPU_FTRS_CELL (CPU_FTR_LWSYNC | \
CPU_FTR_PPCAS_ARCH_V2 | CPU_FTR_CTRL | \
CPU_FTR_ALTIVEC_COMP | CPU_FTR_MMCRA | CPU_FTR_SMT | \
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 1e8b2e04e626..70e043f1dce7 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -384,7 +384,17 @@
#define SPRN_HRMOR 0x139 /* Real mode offset register */
#define SPRN_HSRR0 0x13A /* Hypervisor Save/Restore 0 */
#define SPRN_HSRR1 0x13B /* Hypervisor Save/Restore 1 */
+#define SPRN_HDEXCR_RO 0x1C7 /* Hypervisor DEXCR (non-privileged, readonly) */
+#define SPRN_HASHKEYR 0x1D4 /* Non-privileged hashst/hashchk key register */
+#define SPRN_HDEXCR 0x1D7 /* Hypervisor dynamic execution control register */
+#define SPRN_DEXCR_RO 0x32C /* DEXCR (non-privileged, readonly) */
#define SPRN_ASDR 0x330 /* Access segment descriptor register */
+#define SPRN_DEXCR 0x33C /* Dynamic execution control register */
+#define DEXCR_PR_BIT(aspect) PPC_BIT(32 + (aspect))
+#define DEXCR_PR_SBHE DEXCR_PR_BIT(0) /* Speculative Branch Hint Enable */
+#define DEXCR_PR_IBRTPD DEXCR_PR_BIT(3) /* Indirect Branch Recurrent Target Prediction Disable */
+#define DEXCR_PR_SRAPD DEXCR_PR_BIT(4) /* Subroutine Return Address Prediction Disable */
+#define DEXCR_PR_NPHIE DEXCR_PR_BIT(5) /* Non-Privileged Hash Instruction Enable */
#define SPRN_IC 0x350 /* Virtual Instruction Count */
#define SPRN_VTB 0x351 /* Virtual Time Base */
#define SPRN_LDBAR 0x352 /* LD Base Address Register */
diff --git a/arch/powerpc/kernel/cpu_setup_power.c b/arch/powerpc/kernel/cpu_setup_power.c
index 097c033668f0..c00721801a1b 100644
--- a/arch/powerpc/kernel/cpu_setup_power.c
+++ b/arch/powerpc/kernel/cpu_setup_power.c
@@ -126,6 +126,12 @@ static void init_PMU_ISA31(void)
mtspr(SPRN_MMCR0, MMCR0_FC | MMCR0_PMCCEXT);
}
+static void init_DEXCR(void)
+{
+ mtspr(SPRN_DEXCR, 0);
+ mtspr(SPRN_HASHKEYR, 0);
+}
+
/*
* Note that we can be called twice of pseudo-PVRs.
* The parameter offset is not used.
@@ -241,6 +247,7 @@ void __setup_cpu_power10(unsigned long offset, struct cpu_spec *t)
init_FSCR_power10();
init_PMU();
init_PMU_ISA31();
+ init_DEXCR();
if (!init_hvmode_206(t))
return;
@@ -263,6 +270,7 @@ void __restore_cpu_power10(void)
init_FSCR_power10();
init_PMU();
init_PMU_ISA31();
+ init_DEXCR();
msr = mfmsr();
if (!(msr & MSR_HV))
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 9d9ee4e9e1a1..0b5878c3125b 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -182,6 +182,7 @@ static struct ibm_feature ibm_pa_features[] __initdata = {
.cpu_user_ftrs2 = PPC_FEATURE2_HTM_COMP | PPC_FEATURE2_HTM_NOSC_COMP },
{ .pabyte = 64, .pabit = 0, .cpu_features = CPU_FTR_DAWR1 },
+ { .pabyte = 68, .pabit = 5, .cpu_features = CPU_FTR_DEXCR_NPHIE },
};
/*
--
2.39.2
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