On 08/02/18 16:10, Dave Martin wrote:
On Thu, Feb 08, 2018 at 12:12:37PM +0000, Suzuki K Poulose wrote:
So far we have restricted the scopes for the capabilities
as follows :
1) Errata workaround check are run all CPUs (i.e, always
2) Arm64 features are run only once after the sanitised
feature registers are available using the SCOPE_SYSTEM.
This prevents detecting cpu features that can be detected
on one or more CPUs with SCOPE_LOCAL_CPU (e.g KPTI). Similarly
for errata workaround with SCOPE_SYSTEM.
This patch makes sure that we allow flexibility of having
any scope for a capability. So, we now run through both
arm64_features and arm64_errata in two phases for detection:
a) with SCOPE_LOCAL_CPU filter on each boot time enabled
b) with SCOPE_SYSTEM filter only once after all boot time
enabled CPUs are active.
static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new)
@@ -1387,13 +1389,15 @@ static void verify_local_cpu_errata_workarounds(void)
static void update_cpu_errata_workarounds(void)
In isolation, this looks strange because it seems to handle only a
subset of arm64_errata now.
I think I understand the change as follows:
* all previously-existing errata workarounds SCOPE_LOCAL_CPU
anyway, so the behavior here doesn't change for any existing
* the non SCOPE_SYSTEM workarounds (which this patch prepares for)
"the SCOPE_SYSTEM" workarounds..."
are handled by the new setup_errata_workaround() path.
Similarly, the features handling is split into two: one mirroring
the current behaviour (for SCOPE_SYSTEM this time) and one handling> the rest,
for supporting SCOPE_CPU_LOCAL features in subsequent
Right. The changes here are :
- Run SCOPE_LOCAL_CPU filter on arm64_features on all CPUs (newly added with
this patch) via (newly added)update_cpu_local_features().
Split of existing behavior:
- Run SCOPE_LOCAL_CPU(instead of the earlier SCOPE_ALL) on all CPUs in
- Run SCOPE_SYSTEM filter on arm64_errata, once, via
Does that sound right?
I'm not sure we need extra comments or documentation; I just want
to check that I've understood the patch correctly.
So, would you prefer this split to the original patch ?