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lib: sbi: Revert entry_count before doing hsm stop in hsm wait loop

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Using hsm stop in hsm wait loop causes secondary harts to be stuck
forever in OpenSBI on RISC-V platforms where HSM hart hotplug is
available and all harts come-up at the same time during system
power-on.

For example, lets say we have two harts A and B on a RISC-V platform
with HSM hart hotplug which come-up at the same time during system
power-on. The hart A enters OpenSBI before hart B hence it becomes
the primary (or cold-boot) hart whereas hart B becomes the secondary
(or warm-boot) hart. The hart A follows the OpenSBI cold-boot path
and registers hsm device before hart B enters OpenSBI. The hart B
eventually enters OpenSBI and follows the OpenSBI warm-boot path
so it will increment it's own entry_count before entering hsm wait
loop where it sees hsm device and stops itself. Later as part of
the Linux boot-up sequence, hart A issues SBI HSM start call to
bring-up hart B but OpenSBI sees entry_count != init_count for
hart B in sbi_hsm_hart_start() hence hsm_device_hart_start() is
not called for hart B resulting in hart B stuck forever in OpenSBI.

To fix the above issue, revert entry_count before doing hsm stop
in hsm wait loop.

Fixes: d844deadec ("lib: sbi: Use hsm stop for hsm wait")
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Nick Hu <nick.hu@sifive.com>
Link: https://lore.kernel.org/r/20250527124821.2113467-1-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Anup Patel
2025-05-27 18:18:21 +05:30
committed by Anup Patel
parent 6f8bcae4cb
commit 7dd09bfeca
3 changed files with 18 additions and 1 deletions
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4
lib/sbi/sbi_hsm.c
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@@ -176,8 +176,10 @@ static void sbi_hsm_hart_wait(struct sbi_scratch *scratch)
* If the hsm_dev is ready and it support the hotplug, we can
* use the hsm stop for more power saving
*/
if (hsm_device_has_hart_hotplug())
if (hsm_device_has_hart_hotplug()) {
sbi_revert_entry_count(scratch);
hsm_device_hart_stop();
}
wfi();
}

13
lib/sbi/sbi_init.c
View File

@@ -579,6 +579,19 @@ void __noreturn sbi_init(struct sbi_scratch *scratch)
init_warmboot(scratch, hartid);
}
void sbi_revert_entry_count(struct sbi_scratch *scratch)
{
unsigned long *entry_count, *init_count;
if (!entry_count_offset || !init_count_offset)
sbi_hart_hang();
entry_count = sbi_scratch_offset_ptr(scratch, entry_count_offset);
init_count = sbi_scratch_offset_ptr(scratch, init_count_offset);
*entry_count = *init_count;
}
unsigned long sbi_entry_count(u32 hartindex)
{
struct sbi_scratch *scratch;