* [PATCH] arm64: Use symbolic constants for the ccmp NZCV immediates
@ 2026-10-09 7:21 Fuad Tabba
2026-10-16 4:31 ` Anshuman Khandual
0 siblings, 1 reply; 2+ messages in thread
From: Fuad Tabba @ 2026-10-09 7:21 UTC (permalink / raw)
To: catalin.marinas, will
Cc: mark.rutland, maz, oupton, joey.gouly, suzuki.poulose, yuzenghui,
anshuman.khandual, tabba, linux-arm-kernel, kvmarm, linux-kernel
The ccmp instructions in the EL2 setup code, reset_pmuserenr_el0 and
the hyp vectors give the flags to set when their condition fails as a
raw NZCV immediate, #4 or #8. Which condition that leaves true for the
branch that follows has to be worked out from the pseudocode each time.
Define CCMP_NZCV_EQ and CCMP_NZCV_LT from the PSR bits, named for the
condition each leaves true, and pass those instead.
No functional change intended.
Suggested-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/all/asIQ1ZwUjkmNJbRP@willie-the-truck/
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
arch/arm64/include/asm/assembler.h | 2 +-
arch/arm64/include/asm/el2_setup.h | 4 ++--
arch/arm64/include/asm/ptrace.h | 4 ++++
arch/arm64/kvm/hyp/hyp-entry.S | 2 +-
4 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 0b58b550e8dce..b4b97e03db828 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -500,7 +500,7 @@ alternative_else_nop_endif
mrs \tmpreg, id_aa64dfr0_el1
ubfx \tmpreg, \tmpreg, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
cmp \tmpreg, #ID_AA64DFR0_EL1_PMUVer_NI
- ccmp \tmpreg, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #4, ne
+ ccmp \tmpreg, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #CCMP_NZCV_EQ, ne
b.eq 9000f // Skip if no PMU present or IMP_DEF
msr pmuserenr_el0, xzr // Disable PMU access from EL0
9000:
diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index 1da277baacf78..c0ece880e85bd 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -137,7 +137,7 @@
mrs x1, id_aa64dfr0_el1
ubfx x0, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
cmp x0, #ID_AA64DFR0_EL1_PMUVer_NI
- ccmp x0, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #4, ne
+ ccmp x0, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #CCMP_NZCV_EQ, ne
b.eq .Lskip_pmu_\@ // Skip if no PMU present or IMP_DEF
mrs x0, pmcr_el0 // Disable debug access traps
ubfx x0, x0, #11, #5 // to EL2 and allow access to
@@ -422,7 +422,7 @@
mrs x1, id_aa64dfr0_el1
ubfx x1, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
cmp x1, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF
- ccmp x1, #ID_AA64DFR0_EL1_PMUVer_V3P9, #8, ne
+ ccmp x1, #ID_AA64DFR0_EL1_PMUVer_V3P9, #CCMP_NZCV_LT, ne
b.lt .Lskip_pmuv3p9_\@ // Skip if < PMUv3p9 or IMP_DEF
orr x0, x0, #HDFGRTR2_EL2_nPMICNTR_EL0
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index f7dc5fb9427d6..15c381ef7d2c2 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -30,6 +30,10 @@
#define PSR_MODE_THREAD_BIT (1 << 0)
#define PSR_IL_BIT (1 << 20)
+/* CCMP NZCV immediates that make the named condition hold */
+#define CCMP_NZCV_EQ (PSR_Z_BIT >> 28)
+#define CCMP_NZCV_LT (PSR_N_BIT >> 28)
+
/* AArch32-specific ptrace requests */
#define COMPAT_PTRACE_GETREGS 12
#define COMPAT_PTRACE_SETREGS 13
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 03f97d71984c4..8621eacd13738 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -46,7 +46,7 @@ el1_sync: // Guest trapped into EL2
mrs x0, esr_el2
ubfx x0, x0, #ESR_ELx_EC_SHIFT, #ESR_ELx_EC_WIDTH
cmp x0, #ESR_ELx_EC_HVC64
- ccmp x0, #ESR_ELx_EC_HVC32, #4, ne
+ ccmp x0, #ESR_ELx_EC_HVC32, #CCMP_NZCV_EQ, ne
b.ne el1_trap
/*
--
2.39.5
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] arm64: Use symbolic constants for the ccmp NZCV immediates
2026-10-09 7:21 [PATCH] arm64: Use symbolic constants for the ccmp NZCV immediates Fuad Tabba
@ 2026-10-16 4:31 ` Anshuman Khandual
0 siblings, 0 replies; 2+ messages in thread
From: Anshuman Khandual @ 2026-10-16 4:31 UTC (permalink / raw)
To: Fuad Tabba
Cc: catalin.marinas, will, mark.rutland, maz, oupton, joey.gouly,
suzuki.poulose, yuzenghui, tabba, linux-arm-kernel, kvmarm,
linux-kernel
On Fri, Oct 09, 2026 at 08:21:47AM +0100, Fuad Tabba wrote:
> The ccmp instructions in the EL2 setup code, reset_pmuserenr_el0 and
> the hyp vectors give the flags to set when their condition fails as a
> raw NZCV immediate, #4 or #8. Which condition that leaves true for the
> branch that follows has to be worked out from the pseudocode each time.
>
> Define CCMP_NZCV_EQ and CCMP_NZCV_LT from the PSR bits, named for the
> condition each leaves true, and pass those instead.
>
> No functional change intended.
>
> Suggested-by: Will Deacon <will@kernel.org>
> Link: https://lore.kernel.org/all/asIQ1ZwUjkmNJbRP@willie-the-truck/
> Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> arch/arm64/include/asm/assembler.h | 2 +-
> arch/arm64/include/asm/el2_setup.h | 4 ++--
> arch/arm64/include/asm/ptrace.h | 4 ++++
> arch/arm64/kvm/hyp/hyp-entry.S | 2 +-
> 4 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 0b58b550e8dce..b4b97e03db828 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -500,7 +500,7 @@ alternative_else_nop_endif
> mrs \tmpreg, id_aa64dfr0_el1
> ubfx \tmpreg, \tmpreg, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
> cmp \tmpreg, #ID_AA64DFR0_EL1_PMUVer_NI
> - ccmp \tmpreg, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #4, ne
> + ccmp \tmpreg, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #CCMP_NZCV_EQ, ne
> b.eq 9000f // Skip if no PMU present or IMP_DEF
> msr pmuserenr_el0, xzr // Disable PMU access from EL0
> 9000:
> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
> index 1da277baacf78..c0ece880e85bd 100644
> --- a/arch/arm64/include/asm/el2_setup.h
> +++ b/arch/arm64/include/asm/el2_setup.h
> @@ -137,7 +137,7 @@
> mrs x1, id_aa64dfr0_el1
> ubfx x0, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
> cmp x0, #ID_AA64DFR0_EL1_PMUVer_NI
> - ccmp x0, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #4, ne
> + ccmp x0, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF, #CCMP_NZCV_EQ, ne
> b.eq .Lskip_pmu_\@ // Skip if no PMU present or IMP_DEF
> mrs x0, pmcr_el0 // Disable debug access traps
> ubfx x0, x0, #11, #5 // to EL2 and allow access to
> @@ -422,7 +422,7 @@
> mrs x1, id_aa64dfr0_el1
> ubfx x1, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
> cmp x1, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF
> - ccmp x1, #ID_AA64DFR0_EL1_PMUVer_V3P9, #8, ne
> + ccmp x1, #ID_AA64DFR0_EL1_PMUVer_V3P9, #CCMP_NZCV_LT, ne
> b.lt .Lskip_pmuv3p9_\@ // Skip if < PMUv3p9 or IMP_DEF
>
> orr x0, x0, #HDFGRTR2_EL2_nPMICNTR_EL0
> diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
> index f7dc5fb9427d6..15c381ef7d2c2 100644
> --- a/arch/arm64/include/asm/ptrace.h
> +++ b/arch/arm64/include/asm/ptrace.h
> @@ -30,6 +30,10 @@
> #define PSR_MODE_THREAD_BIT (1 << 0)
> #define PSR_IL_BIT (1 << 20)
>
> +/* CCMP NZCV immediates that make the named condition hold */
> +#define CCMP_NZCV_EQ (PSR_Z_BIT >> 28)
> +#define CCMP_NZCV_LT (PSR_N_BIT >> 28)
> +
> /* AArch32-specific ptrace requests */
> #define COMPAT_PTRACE_GETREGS 12
> #define COMPAT_PTRACE_SETREGS 13
> diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
> index 03f97d71984c4..8621eacd13738 100644
> --- a/arch/arm64/kvm/hyp/hyp-entry.S
> +++ b/arch/arm64/kvm/hyp/hyp-entry.S
> @@ -46,7 +46,7 @@ el1_sync: // Guest trapped into EL2
> mrs x0, esr_el2
> ubfx x0, x0, #ESR_ELx_EC_SHIFT, #ESR_ELx_EC_WIDTH
> cmp x0, #ESR_ELx_EC_HVC64
> - ccmp x0, #ESR_ELx_EC_HVC32, #4, ne
> + ccmp x0, #ESR_ELx_EC_HVC32, #CCMP_NZCV_EQ, ne
> b.ne el1_trap
>
> /*
> --
> 2.39.5
>
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2026-10-16 4:31 ` Anshuman Khandual
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