On 09/25/2018 04:13 PM, Marc Zyngier wrote:

On 25/09/18 04:10, Yao Lihua wrote:

quoted

Hi Marc, Julien?


On 09/21/2018 11:56 PM, Marc Zyngier wrote:

quoted

On Tue, 28 Aug 2018 16:51:11 +0100,
Julien Thierry [off-list ref] wrote:

quoted

Signed-off-by: Julien Thierry <redacted>
Suggested-by: Daniel Thompson <redacted>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <redacted>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Marc Zyngier <redacted>
---
? arch/arm64/kernel/cpufeature.c | 2 +-
? 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index e238b79..1e433ac 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c

@@ -1039,7 +1039,7 @@ static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused)

????? {
????????? .desc = "GIC system register CPU interface",
????????? .capability = ARM64_HAS_SYSREG_GIC_CPUIF,
-??????? .type = ARM64_CPUCAP_SYSTEM_FEATURE,
+??????? .type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
????????? .matches = has_useable_gicv3_cpuif,
????????? .sys_reg = SYS_ID_AA64PFR0_EL1,
????????? .field_pos = ID_AA64PFR0_GIC_SHIFT,
--?
1.9.1

This definitely deserves a commit message, such as:

"We do not support systems where some CPUs have an operational GICv3
? CPU interface, and some don't. Let's make this requirement obvious by
? flagging the GICv3 capability as being strict."

May I ask if it is possible to implement psedue-NMI on a arm64 SoC with GIC-400?

In theory, yes. In practice, this is likely to be both hard to implement (you need to discover the GIC CPU interface address very early so that you can patch the the PMR flipping code at the right time), and pretty bad from a performance point of view (MMIO accesses are likely to be slow).

Given the above, the incentive to support such a configuration is close to zero.

Hi Marc,

Thank you for the answer!

I intended to utilize hard lockup detector and on-demand CPU backtrace to debug a nasty BUG. But it seem a hardware debugger would be much easier.:-)

Best Regards,
Lihua