* [PATCH V2] x86/sgx: Silence softlockup detection when releasing large enclaves
@ 2022-01-25 18:22 Reinette Chatre
2022-01-26 14:32 ` Jarkko Sakkinen
0 siblings, 1 reply; 2+ messages in thread
From: Reinette Chatre @ 2022-01-25 18:22 UTC (permalink / raw)
To: dave.hansen, jarkko, tglx, bp, luto, mingo, linux-sgx, x86
Cc: vijay.dhanraj, linux-kernel, stable
Vijay reported that the "unclobbered_vdso_oversubscribed" selftest
triggers the softlockup detector.
Actual SGX systems have 128GB of enclave memory or more. The
"unclobbered_vdso_oversubscribed" selftest creates one enclave which
consumes all of the enclave memory on the system. Tearing down such a
large enclave takes around a minute, most of it in the loop where
the EREMOVE instruction is applied to each individual 4k enclave page.
Spending one minute in a loop triggers the softlockup detector.
Add a cond_resched() to give other tasks a chance to run and placate
the softlockup detector.
Cc: stable@vger.kernel.org
Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer")
Reported-by: Vijay Dhanraj <vijay.dhanraj@intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
Softlockup message:
watchdog: BUG: soft lockup - CPU#7 stuck for 22s! [test_sgx:11502]
Kernel panic - not syncing: softlockup: hung tasks
<snip>
sgx_encl_release+0x86/0x1c0
sgx_release+0x11c/0x130
__fput+0xb0/0x280
____fput+0xe/0x10
task_work_run+0x6c/0xc0
exit_to_user_mode_prepare+0x1eb/0x1f0
syscall_exit_to_user_mode+0x1d/0x50
do_syscall_64+0x46/0xb0
entry_SYSCALL_64_after_hwframe+0x44/0xae
Changes since V1:
- V1: https://lore.kernel.org/lkml/1aa037705e5aa209d8b7a075873c6b4190327436.1642530802.git.reinette.chatre@intel.com/
- Add comment provided by Jarkko.
arch/x86/kernel/cpu/sgx/encl.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 001808e3901c..48afe96ae0f0 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -410,6 +410,8 @@ void sgx_encl_release(struct kref *ref)
}
kfree(entry);
+ /* Invoke scheduler to prevent soft lockups. */
+ cond_resched();
}
xa_destroy(&encl->page_array);
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH V2] x86/sgx: Silence softlockup detection when releasing large enclaves
2022-01-25 18:22 [PATCH V2] x86/sgx: Silence softlockup detection when releasing large enclaves Reinette Chatre
@ 2022-01-26 14:32 ` Jarkko Sakkinen
0 siblings, 0 replies; 2+ messages in thread
From: Jarkko Sakkinen @ 2022-01-26 14:32 UTC (permalink / raw)
To: Reinette Chatre
Cc: dave.hansen, tglx, bp, luto, mingo, linux-sgx, x86,
vijay.dhanraj, linux-kernel, stable
On Tue, Jan 25, 2022 at 10:22:43AM -0800, Reinette Chatre wrote:
> Vijay reported that the "unclobbered_vdso_oversubscribed" selftest
> triggers the softlockup detector.
>
> Actual SGX systems have 128GB of enclave memory or more. The
> "unclobbered_vdso_oversubscribed" selftest creates one enclave which
> consumes all of the enclave memory on the system. Tearing down such a
> large enclave takes around a minute, most of it in the loop where
> the EREMOVE instruction is applied to each individual 4k enclave page.
>
> Spending one minute in a loop triggers the softlockup detector.
>
> Add a cond_resched() to give other tasks a chance to run and placate
> the softlockup detector.
>
> Cc: stable@vger.kernel.org
> Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer")
> Reported-by: Vijay Dhanraj <vijay.dhanraj@intel.com>
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
> Softlockup message:
>
> watchdog: BUG: soft lockup - CPU#7 stuck for 22s! [test_sgx:11502]
> Kernel panic - not syncing: softlockup: hung tasks
> <snip>
> sgx_encl_release+0x86/0x1c0
> sgx_release+0x11c/0x130
> __fput+0xb0/0x280
> ____fput+0xe/0x10
> task_work_run+0x6c/0xc0
> exit_to_user_mode_prepare+0x1eb/0x1f0
> syscall_exit_to_user_mode+0x1d/0x50
> do_syscall_64+0x46/0xb0
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Changes since V1:
> - V1: https://lore.kernel.org/lkml/1aa037705e5aa209d8b7a075873c6b4190327436.1642530802.git.reinette.chatre@intel.com/
> - Add comment provided by Jarkko.
>
> arch/x86/kernel/cpu/sgx/encl.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index 001808e3901c..48afe96ae0f0 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -410,6 +410,8 @@ void sgx_encl_release(struct kref *ref)
> }
>
> kfree(entry);
> + /* Invoke scheduler to prevent soft lockups. */
> + cond_resched();
> }
>
> xa_destroy(&encl->page_array);
> --
> 2.25.1
>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Jarkko Sakkinen <jarkko@kernel.org> (kselftest as sanity check)
BR, Jarkko
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