Hi Pranav,
Please see my response inline marked [SAMI].
Regards,
Sami Mujawar
On 11/03/2022 06:06 AM, Pranav Madhu wrote:
Hi Sami,
Thanks for your comments. Please find my reply inline.
Regards,
Pranav
-----Original Message-----
From: Sami Mujawar <sami.muja...@arm.com>
Sent: Thursday, March 10, 2022 9:01 PM
To: Pranav Madhu <pranav.ma...@arm.com>; devel@edk2.groups.io
Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org>; nd <n...@arm.com>
Subject: Re: [edk2][PATCH V1 1/1] ArmPkg: Handle warm reboot request
correctly
Hi Pranav,
Thank you for this patch.
Please find my response inline marked [SAMI].
Regards,
Sami Mujawar
On 10/03/2022 01:10 PM, Pranav Madhu wrote:
The warm reboot requests are mapped to cold reboot as the power
control module was not capable of handling the warm reboot requests in
the legacy implementation. The support for warm reboot support is
added into the power control module. To support warm reset, update
ArmPsciResetSystemLib, and there by invoke the PSCI call with
parameters for warm reboot.
Signed-off-by: Pranav Madhu <pranav.ma...@arm.com>
---
ArmPkg/Include/IndustryStandard/ArmStdSmc.h | 1 +
ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c | 7
+++++--
2 files changed, 6 insertions(+), 2 deletions(-)
Link to github branch for this patch -
https://github.com/Pranav-Madhu/edk2/tree/topics/warm_reboot
diff --git a/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
b/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
index 655edc21b205..c9059dead6e9 100644
--- a/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
+++ b/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
@@ -93,6 +93,7 @@
#define ARM_SMC_ID_PSCI_MIGRATE_AARCH32 0x84000005
#define ARM_SMC_ID_PSCI_SYSTEM_OFF 0x84000008
#define ARM_SMC_ID_PSCI_SYSTEM_RESET 0x84000009
+#define ARM_SMC_ID_PSCI_SYSTEM_RESET2_AARCH64 0xc4000012
/* The current PSCI version is: 0.2 */
#define ARM_SMC_PSCI_VERSION_MAJOR 0 diff --git
a/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
b/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
index 7bcd34849507..27e048ba0f7a 100644
--- a/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
+++ b/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
@@ -45,10 +45,13 @@ LibResetSystem (
ARM_SMC_ARGS ArmSmcArgs;
switch (ResetType) {
+ case EfiResetWarm:
+ ArmSmcArgs.Arg0 = ARM_SMC_ID_PSCI_SYSTEM_RESET2_AARCH64;
+ ArmSmcArgs.Arg1 = 0;
+ ArmSmcArgs.Arg2 = 0;
+ break;
[SAMI] SYSTEM_RESET2 is an optional feature and if not supported would
return NOT_SUPPORTED. So, if a platform does not support SYSTEM_RESET2,
should the code here fall back to SYSTEM_RESET?
According to the PSCI specification, it is the responsibility of the OS to check
that SYSTEM_RESET2 is supported before calling SYSTEM_RESET2 (I believe this
is applicable for the case where UEFI is not used to boot the OS). However, if
the runtime service ResetSystem() is invoked by the OS requesting a warm
reset, is it not the firmware's responsibility to ensure that SYSTEM_RESET2 is
supported? Any thoughts?
Right, from PSCI specification, what I understood is before invoking
SYSTEM_RESET2, the OS should query the PSCI capabilities using PSCI_FEATURES
for SYSTEM_RESET2. The OS should invoke RESET2 only if PSCI_FEATURES returns 0.
From spec, what I understood is it is not the responsibility of firmware. If OS
issue RESET2 without querying FEATURES, the only option for firmware is to
return NOT_SUPPORTED.
[SAMI] There are 2 scenarios:
1. A boot loader other than UEFI is used to boot the OS.
In this case the OS shall directly call the PSCI interface to reboot.
For this scenario the Linux kernel code performs the required checks and
makes the appropriate PSCI call see
https://elixir.bootlin.com/linux/v5.16.13/source/drivers/firmware/psci/psci.c#L299
2. UEFI is used to boot the OS.
In this case the UEFI Runtime Services ResetSystem() will be invoked by
the OS to initiate a reboot.
In this scenario the checks performed by the OS to see if SYSTEM_RESET2
is supported are irrelevant. It is the firmware that needs to perform
the check. Although
the PSCI specification section '5.12.4 Caller responsibilities' mentions
'The calling OS...'; this is an example, and in context with the current
usage scenario, it is the
responsibility of the firmware (the Caller) to perform these checks.
Otherwise this can result in failures on platforms that do not implement
the SYSTEM_RESET2 feature.
The relevant code in the Linux kernel for this scenario can be seen at:
https://elixir.bootlin.com/linux/v5.16.13/source/drivers/firmware/efi/reboot.c#L13
https://elixir.bootlin.com/linux/v5.16.13/source/drivers/firmware/efi/runtime-wrappers.c#L412
I also noticed that there are 2 versions of the ResetSystem library:
[A] EfiResetSystemLib based implementation
This is
ArmPkg\Library\ArmPsciResetSystemLib\ArmPsciResetSystemLib.inf which
links with EmbeddedPkg/ResetRuntimeDxe/ResetRuntimeDxe.inf
[B] ResetSystemLib based implementation
This is
ArmPkg\Library\ArmSmcPsciResetSystemLib\ArmSmcPsciResetSystemLib.inf
which links with
MdeModulePkg/Universal/ResetSystemRuntimeDxe/ResetSystemRuntimeDxe.inf
I can see that [A] EfiResetSystemLib is only used by:
- Platform/ARM/SgiPkg/SgiPlatform.dsc.inc
- Silicon/Ampere/AmpereAltraPkg/AmpereAltraPkg.dsc.inc
- Silicon/Phytium/PhytiumCommonPkg/PhytiumCommonPkg.dsc.inc
Moreover, the commit b2c55e732888fd721f5235a820b1d1c45209992d states
that the ArmSmcPsciResetSystemLib.inf ([B] ResetSystemLib) was introduced
with the intention to replace the EfiResetSystemLib based implementation
that is deprecated now that we have decided that there is
no longer a reason to keep a different ResetSystem() implementation
under EmbeddedPkg.
Considering this, I don't think this patch should modify
ArmPkg\Library\ArmPsciResetSystemLib.
SgiPkg (and if possible other platforms) should consider moving to
ResetSystemLib based implementation.
[/SAMI]
[/SAMI]
case EfiResetPlatformSpecific:
// Map the platform specific reset as reboot
- case EfiResetWarm:
- // Map a warm reset into a cold reset
case EfiResetCold:
// Send a PSCI 0.2 SYSTEM_RESET command
ArmSmcArgs.Arg0 = ARM_SMC_ID_PSCI_SYSTEM_RESET;
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#87464): https://edk2.groups.io/g/devel/message/87464
Mute This Topic: https://groups.io/mt/89685482/21656
Group Owner: devel+ow...@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com]
-=-=-=-=-=-=-=-=-=-=-=-