Re: [PATCH v3 15/22] arm64: capabilities: Change scope of VHE to Boot CPU feature
On Thu, Mar 08, 2018 at 12:10:22PM +, Suzuki K Poulose wrote: > On 12/02/18 17:17, Dave Martin wrote: > >On Fri, Feb 09, 2018 at 05:54:59PM +, Suzuki K Poulose wrote: > >>We expect all CPUs to be running at the same EL inside the kernel > >>with or without VHE enabled and we have strict checks to ensure > >>that any mismatch triggers a kernel panic. If VHE is enabled, > >>we use the feature based on the boot CPU and all other CPUs > >>should follow. This makes it a perfect candidate for a cpability > > > >capability > > > >>based on the boot CPU, which should be matched by all the CPUs > >>(both when is ON and OFF). This saves us some not-so-pretty > >>hooks and special code, just for verifying the conflict. > >> > >>Cc: Marc Zyngier > >>Cc: Dave Martin > >>Cc: Will Deacon > >>Signed-off-by: Suzuki K Poulose > >>--- > >> arch/arm64/include/asm/cpufeature.h | 7 +++ > >> arch/arm64/include/asm/virt.h | 6 -- > >> arch/arm64/kernel/cpufeature.c | 5 +++-- > >> arch/arm64/kernel/smp.c | 38 > >> - > >> 4 files changed, 10 insertions(+), 46 deletions(-) > >> > >>diff --git a/arch/arm64/include/asm/cpufeature.h > >>b/arch/arm64/include/asm/cpufeature.h > >>index 5f56a8342065..dfce93f79ae7 100644 > >>--- a/arch/arm64/include/asm/cpufeature.h > >>+++ b/arch/arm64/include/asm/cpufeature.h > >>@@ -276,6 +276,13 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; > >>(ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ > >> ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU) > >>+/* > >>+ * Critical CPU feature used early in the boot based on the boot CPU. > >>+ * The feature should be matched by all booting CPU (both miss and hit > >>+ * cases). > >>+ */ > >>+#define ARM64_CPUCAP_CRITICAL_BOOT_CPU_FEATURE ARM64_CPUCAP_SCOPE_BOOT_CPU > >>+ > > > >Nit: would it be consistent with the uses we already have for the word > >"strict" to use that word here? i.e., > >ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE. > >Or do you think that would be more confusing? > > We don't use the "STRICT" tag anymore. Moreover, I used CRITICAL to indicate > that it is special in a way that all the "late" CPUs (in this case all > secondaries) should match the "state" of the capability (i.e, both ON and > OFF) > as that of the boot CPU. I am OK to change it to STRICT. OK, I think so long as the definition is clear the precise name doesn't matter too much. I suggest deleting "critical" from the comment though, since that suggests a circular definition. The meaning seems clear(er) without it. [...] Cheers ---Dave
Re: [PATCH v3 15/22] arm64: capabilities: Change scope of VHE to Boot CPU feature
On 12/02/18 17:17, Dave Martin wrote:
On Fri, Feb 09, 2018 at 05:54:59PM +, Suzuki K Poulose wrote:
We expect all CPUs to be running at the same EL inside the kernel
with or without VHE enabled and we have strict checks to ensure
that any mismatch triggers a kernel panic. If VHE is enabled,
we use the feature based on the boot CPU and all other CPUs
should follow. This makes it a perfect candidate for a cpability
capability
based on the boot CPU, which should be matched by all the CPUs
(both when is ON and OFF). This saves us some not-so-pretty
hooks and special code, just for verifying the conflict.
Cc: Marc Zyngier
Cc: Dave Martin
Cc: Will Deacon
Signed-off-by: Suzuki K Poulose
---
arch/arm64/include/asm/cpufeature.h | 7 +++
arch/arm64/include/asm/virt.h | 6 --
arch/arm64/kernel/cpufeature.c | 5 +++--
arch/arm64/kernel/smp.c | 38 -
4 files changed, 10 insertions(+), 46 deletions(-)
diff --git a/arch/arm64/include/asm/cpufeature.h
b/arch/arm64/include/asm/cpufeature.h
index 5f56a8342065..dfce93f79ae7 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -276,6 +276,13 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
(ARM64_CPUCAP_SCOPE_LOCAL_CPU | \
ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU)
+/*
+ * Critical CPU feature used early in the boot based on the boot CPU.
+ * The feature should be matched by all booting CPU (both miss and hit
+ * cases).
+ */
+#define ARM64_CPUCAP_CRITICAL_BOOT_CPU_FEATURE ARM64_CPUCAP_SCOPE_BOOT_CPU
+
Nit: would it be consistent with the uses we already have for the word
"strict" to use that word here? i.e.,
ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE.
Or do you think that would be more confusing?
We don't use the "STRICT" tag anymore. Moreover, I used CRITICAL to indicate
that it is special in a way that all the "late" CPUs (in this case all
secondaries) should match the "state" of the capability (i.e, both ON and OFF)
as that of the boot CPU. I am OK to change it to STRICT.
Otherwise, "critical" sounds a bit like we depend on the capability
being available.
If "strict" doesn't fit though and no other option suggests itself,
it's probably not worth changing this.
struct arm64_cpu_capabilities {
const char *desc;
u16 capability;
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index c5f89442785c..9d1e24e030b3 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -102,12 +102,6 @@ static inline bool has_vhe(void)
return false;
}
-#ifdef CONFIG_ARM64_VHE
-extern void verify_cpu_run_el(void);
-#else
-static inline void verify_cpu_run_el(void) {}
-#endif
-
#endif /* __ASSEMBLY__ */
#endif /* ! __ASM__VIRT_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 7625e2962e2b..f66e66c79916 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1016,11 +1016,13 @@ static const struct arm64_cpu_capabilities
arm64_features[] = {
},
#endif /* CONFIG_ARM64_PAN */
{
+#ifdef CONFIG_ARM64_VHE
.desc = "Virtualization Host Extensions",
.capability = ARM64_HAS_VIRT_HOST_EXTN,
- .type = ARM64_CPUCAP_SYSTEM_FEATURE,
+ .type = ARM64_CPUCAP_CRITICAL_BOOT_CPU_FEATURE,
.matches = runs_at_el2,
.cpu_enable = cpu_copy_el2regs,
+#endif
Shouldn't the #ifdef...#endif be outside the { ... },?
Otherwise this yields an empty block that will truncate the list in the
CONFIG_ARM64_VHE case...
Good catch. You're right, I will fix it.
Removal of this block for !CONFIG_ARM64_VHE is a change rather than just
refactoring, so the commit message should explain it.
Ok.
Cheers
Suzuki
Re: [PATCH v3 15/22] arm64: capabilities: Change scope of VHE to Boot CPU feature
On Fri, Feb 09, 2018 at 05:54:59PM +, Suzuki K Poulose wrote:
> We expect all CPUs to be running at the same EL inside the kernel
> with or without VHE enabled and we have strict checks to ensure
> that any mismatch triggers a kernel panic. If VHE is enabled,
> we use the feature based on the boot CPU and all other CPUs
> should follow. This makes it a perfect candidate for a cpability
capability
> based on the boot CPU, which should be matched by all the CPUs
> (both when is ON and OFF). This saves us some not-so-pretty
> hooks and special code, just for verifying the conflict.
>
> Cc: Marc Zyngier
> Cc: Dave Martin
> Cc: Will Deacon
> Signed-off-by: Suzuki K Poulose
> ---
> arch/arm64/include/asm/cpufeature.h | 7 +++
> arch/arm64/include/asm/virt.h | 6 --
> arch/arm64/kernel/cpufeature.c | 5 +++--
> arch/arm64/kernel/smp.c | 38
> -
> 4 files changed, 10 insertions(+), 46 deletions(-)
>
> diff --git a/arch/arm64/include/asm/cpufeature.h
> b/arch/arm64/include/asm/cpufeature.h
> index 5f56a8342065..dfce93f79ae7 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -276,6 +276,13 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
> (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \
>ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU)
>
> +/*
> + * Critical CPU feature used early in the boot based on the boot CPU.
> + * The feature should be matched by all booting CPU (both miss and hit
> + * cases).
> + */
> +#define ARM64_CPUCAP_CRITICAL_BOOT_CPU_FEATURE ARM64_CPUCAP_SCOPE_BOOT_CPU
> +
Nit: would it be consistent with the uses we already have for the word
"strict" to use that word here? i.e.,
ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE.
Or do you think that would be more confusing?
Otherwise, "critical" sounds a bit like we depend on the capability
being available.
If "strict" doesn't fit though and no other option suggests itself,
it's probably not worth changing this.
> struct arm64_cpu_capabilities {
> const char *desc;
> u16 capability;
> diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
> index c5f89442785c..9d1e24e030b3 100644
> --- a/arch/arm64/include/asm/virt.h
> +++ b/arch/arm64/include/asm/virt.h
> @@ -102,12 +102,6 @@ static inline bool has_vhe(void)
> return false;
> }
>
> -#ifdef CONFIG_ARM64_VHE
> -extern void verify_cpu_run_el(void);
> -#else
> -static inline void verify_cpu_run_el(void) {}
> -#endif
> -
> #endif /* __ASSEMBLY__ */
>
> #endif /* ! __ASM__VIRT_H */
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 7625e2962e2b..f66e66c79916 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1016,11 +1016,13 @@ static const struct arm64_cpu_capabilities
> arm64_features[] = {
> },
> #endif /* CONFIG_ARM64_PAN */
> {
> +#ifdef CONFIG_ARM64_VHE
> .desc = "Virtualization Host Extensions",
> .capability = ARM64_HAS_VIRT_HOST_EXTN,
> - .type = ARM64_CPUCAP_SYSTEM_FEATURE,
> + .type = ARM64_CPUCAP_CRITICAL_BOOT_CPU_FEATURE,
> .matches = runs_at_el2,
> .cpu_enable = cpu_copy_el2regs,
> +#endif
Shouldn't the #ifdef...#endif be outside the { ... },?
Otherwise this yields an empty block that will truncate the list in the
CONFIG_ARM64_VHE case...
Removal of this block for !CONFIG_ARM64_VHE is a change rather than just
refactoring, so the commit message should explain it.
[...]
Cheers
---Dave
