Hi
> On 31 Jan 2024, at 15:49, Russell King wrote:
>
> From: James Morse
>
> Today the ACPI enumeration code 'visits' all devices that are present.
>
> This is a problem for arm64, where CPUs are always present, but not
> always enabled. When a device-check occurs because the firmware-policy
From: James Morse
Add a description of physical and virtual CPU hotplug, explain the
differences and elaborate on what is required in ACPI for a working
virtual hotplug system.
Signed-off-by: James Morse
Reviewed-by: Jonathan Cameron
Signed-off-by: Russell King (Oracle)
---
Outstanding
From: James Morse
acpi_processor_get_info() registers all present CPUs. Registering a
CPU is what creates the sysfs entries and triggers the udev
notifications.
arm64 virtual machines that support 'virtual cpu hotplug' use the
enabled bit to indicate whether the CPU can be brought online, as
From: James Morse
The 'offline' file in sysfs shows all offline CPUs, including those
that aren't present. User-space is expected to remove not-present CPUs
from this list to learn which CPUs could be brought online.
CPUs can be present but not-enabled. These CPUs can't be brought online
until
From: James Morse
struct acpi_scan_handler has a detach callback that is used to remove
a driver when a bus is changed. When interacting with an eject-request,
the detach callback is called before _EJ0.
This means the ACPI processor driver can't use _STA to determine if a
CPU has been made
Rather than ifdef'ing acpi_processor_post_eject() and its use site, use
IS_ENABLED() to increase compile coverage.
Reviewed-by: Jonathan Cameron
Signed-off-by: Russell King (Oracle)
---
drivers/acpi/acpi_processor.c | 7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git
From: Jean-Philippe Brucker
When a CPU is marked as disabled, but online capable in the MADT, PSCI
applies some firmware policy to control when it can be brought online.
PSCI returns DENIED to a CPU_ON request if this is not currently
permitted. The OS can learn the current policy from the _STA
From: James Morse
To support virtual CPU hotplug, ACPI has added an 'online capable' bit
to the MADT GICC entries. This indicates a disabled CPU entry may not
be possible to online via PSCI until firmware has set enabled bit in
_STA.
This means that a "usable" GIC is one that is marked as
From: James Morse
acpi_processor_hotadd_init() will make a CPU present by mapping it
based on its hardware id.
'hotadd_init' is ambiguous once there are two different behaviours
for cpu hotplug. This is for toggling the _STA present bit. Subsequent
patches will add support for toggling the _STA
From: James Morse
gic_acpi_match_gicc() is only called via gic_acpi_count_gicr_regions().
It should only count the number of enabled redistributors, but it
also tries to sanity check the GICC entry, currently returning an
error if the Enabled bit is set, but the gicr_base_address is zero.
From: James Morse
ACPI firmware can trigger the events to add and remove CPUs, but the
OS may not support this.
Print an error message when this happens.
This gives early warning on arm64 systems that don't support
CONFIG_ACPI_HOTPLUG_PRESENT_CPU, as making CPUs not present has
side effects
From: James Morse
ACPI identifies CPUs by UID. get_cpu_for_acpi_id() maps the ACPI UID
to the linux CPU number.
The helper to retrieve this mapping is only available in arm64's numa
code.
Move it to live next to get_acpi_id_for_cpu().
Signed-off-by: James Morse
Reviewed-by: Jonathan Cameron
From: James Morse
When called acpi_processor_post_eject() unconditionally make a CPU
not-present and unregisters it.
To add support for AML events where the CPU has become disabled, but
remains present, the _STA method should be checked before calling
acpi_processor_remove().
Rename
From: James Morse
Today the ACPI enumeration code 'visits' all devices that are present.
This is a problem for arm64, where CPUs are always present, but not
always enabled. When a device-check occurs because the firmware-policy
has changed and a CPU is now enabled, the following error occurs:
|
From: James Morse
A subsequent patch will change acpi_scan_hot_remove() to call
acpi_bus_trim_one() instead of acpi_bus_trim(), meaning it can no longer
rely on the prototype in the header file.
Move these functions further up the file.
No change in behaviour.
Signed-off-by: James Morse
From: James Morse
To allow ACPI to skip the call to arch_register_cpu() when the _STA
value indicates the CPU can't be brought online right now, move the
arch_register_cpu() call into acpi_processor_get_info().
Systems can still be booted with 'acpi=off', or not include an
ACPI description at
Hi,
This is another iteration of the Arm64 virtual CPU hotplug support,
updated for the review comments on the v3 smaller series posted back
in December.
I believe all feedback has been addressed - if I have missed something
then please accept my apologies. Several patches have been dropped from
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