Hi Michal,
On 12/10/2021 09:13, Michal Orzel wrote:
ID_AA64DFR0_EL1/ID_DFR0_EL1 registers provide
information about PMU support. Replace structure
dbg64/dbg32 with a union and fill in all the
register fields according to document:
ARM Architecture Registers(DDI 0595, 2021-06).
Add macros boot_dbg_feature64/boot_dbg_feature32
to check for a debug feature. Add macro
cpu_has_pmu to check for PMU support.
Any value higher than 0 and less than 15 means
that PMU is supported (we do not care about its
version for now).
Signed-off-by: Michal Orzel <michal.or...@arm.com>
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
Reviewed-by: Bertrand Marquis <bertrand.marq...@arm.com>
---
Changes since v4:
-improve checks for PMU
Changes since v3:
-none
Changes since v2:
-none
Changes since v1:
-new in v2
---
xen/include/asm-arm/cpufeature.h | 51 ++++++++++++++++++++++++++++++--
1 file changed, 49 insertions(+), 2 deletions(-)
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index 5ca09b0bff..0ddf38858a 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -4,6 +4,7 @@
#ifdef CONFIG_ARM_64
#define cpu_feature64(c, feat) ((c)->pfr64.feat)
#define boot_cpu_feature64(feat) (system_cpuinfo.pfr64.feat)
+#define boot_dbg_feature64(feat) (system_cpuinfo.dbg64.feat)
#define cpu_feature64_has_el0_32(c) (cpu_feature64(c, el0) == 2)
@@ -22,6 +23,7 @@
#define cpu_feature32(c, feat) ((c)->pfr32.feat)
#define boot_cpu_feature32(feat) (system_cpuinfo.pfr32.feat)
+#define boot_dbg_feature32(feat) (system_cpuinfo.dbg32.feat)
#define cpu_has_arm (boot_cpu_feature32(arm) == 1)
#define cpu_has_thumb (boot_cpu_feature32(thumb) >= 1)
@@ -32,8 +34,12 @@
#ifdef CONFIG_ARM_32
#define cpu_has_gentimer (boot_cpu_feature32(gentimer) == 1)
+#define cpu_has_pmu ((boot_dbg_feature32(perfmon) >= 1) && \
+ (boot_dbg_feature32(perfmon) < 15))
So I am happy with this check for arm32. But I would still like to have
a comment explaining the fact that on Armv7 perfmon == 0 may mean PMUv1
is may be used. Something like:
"On Armv7, the value 0 is used to indicate that PMUv2 is not supported.
IOW this doesn't tell us whether the PMU is not supported (a processor
may implement PMUv1).
For convenience, we treat 0 as not supported which this match the
meaning on Armv8".
The rest of the code looks fine to me.
Cheers,
--
Julien Grall
