Hibernation support depends on firmware marking its reserved/PMP
protected regions as not accessible from Linux.
The latest versions of the de-facto SBI implementation (OpenSBI) do
not do this, having dropped the no-map property to enable 1 GiB huge
page mappings by the kernel.
This was exposed by commit 3335068f8721 ("riscv: Use PUD/P4D/PGD pages
for the linear mapping"), which made the first 2 MiB of DRAM (where SBI
typically resides) accessible by the kernel.
Attempting to hibernate with either OpenSBI, or other implementations
following its lead, will lead to a kernel panic ([1], [2]) as the
hibernation process will attempt to save/restore any mapped regions,
including the PMP protected regions in use by the SBI implementation.
Mark hibernation as depending on "NONPORTABLE", as only a small subset
of systems are capable of supporting it, until such time that an SBI
implementation independent way to communicate what regions are in use
has been agreed on.
As hibernation support landed in v6.4-rc1, disabling it for most
platforms does not constitute a regression. The alternative would have
been reverting commit 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for
the linear mapping").
Doing so would permit hibernation on platforms with these SBI
implementations, but would limit the options we have to solve the
protection of the region without causing a regression in hibernation
support.
Reported-by: Song Shuai <[email protected]>
Link: https://lore.kernel.org/all/CAAYs2=gQvkhTeioMmqRDVGjdtNF_vhB+vm_1dHJxPNi75YDQ_Q@mail.gmail.com/ [1]
Reported-by: JeeHeng Sia <[email protected]>
Link: https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/ITXwaKfA6z8 [2]
Signed-off-by: Conor Dooley <[email protected]>
---
arch/riscv/Kconfig | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 13f058490608..117d53785560 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -800,8 +800,11 @@ menu "Power management options"
source "kernel/power/Kconfig"
+# Hibernation is only possible on systems where the SBI implementation has
+# marked its reserved memory as not accessible from, or does not run
+# from the same memory as, Linux
config ARCH_HIBERNATION_POSSIBLE
- def_bool y
+ def_bool NONPORTABLE
config ARCH_HIBERNATION_HEADER
def_bool HIBERNATION
--
2.39.2
On Fri, 26 May 2023 11:59:08 +0100, Conor Dooley wrote:
> Hibernation support depends on firmware marking its reserved/PMP
> protected regions as not accessible from Linux.
> The latest versions of the de-facto SBI implementation (OpenSBI) do
> not do this, having dropped the no-map property to enable 1 GiB huge
> page mappings by the kernel.
> This was exposed by commit 3335068f8721 ("riscv: Use PUD/P4D/PGD pages
> for the linear mapping"), which made the first 2 MiB of DRAM (where SBI
> typically resides) accessible by the kernel.
> Attempting to hibernate with either OpenSBI, or other implementations
> following its lead, will lead to a kernel panic ([1], [2]) as the
> hibernation process will attempt to save/restore any mapped regions,
> including the PMP protected regions in use by the SBI implementation.
>
> [...]
Applied, thanks!
[1/1] RISC-V: mark hibernation as nonportable
https://git.kernel.org/palmer/c/ed309ce52218
Best regards,
--
Palmer Dabbelt <[email protected]>
Hello:
This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <[email protected]>:
On Fri, 26 May 2023 11:59:08 +0100 you wrote:
> Hibernation support depends on firmware marking its reserved/PMP
> protected regions as not accessible from Linux.
> The latest versions of the de-facto SBI implementation (OpenSBI) do
> not do this, having dropped the no-map property to enable 1 GiB huge
> page mappings by the kernel.
> This was exposed by commit 3335068f8721 ("riscv: Use PUD/P4D/PGD pages
> for the linear mapping"), which made the first 2 MiB of DRAM (where SBI
> typically resides) accessible by the kernel.
> Attempting to hibernate with either OpenSBI, or other implementations
> following its lead, will lead to a kernel panic ([1], [2]) as the
> hibernation process will attempt to save/restore any mapped regions,
> including the PMP protected regions in use by the SBI implementation.
>
> [...]
Here is the summary with links:
- [v1] RISC-V: mark hibernation as nonportable
https://git.kernel.org/riscv/c/ed309ce52218
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html