On 13/02/2024 14:21, Marc Zyngier wrote:
On Tue, 13 Feb 2024 11:14:37 +0000,
Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote:
Hi
On 12.02.2024 15:47, Marc Zyngier wrote:
We handle ID_AA64MMFR4_EL1.E2H0 being 0 as NV1 being present.
However, this is only true if FEAT_NV is implemented.
Add the required check to has_nv1(), avoiding spuriously advertising
NV1 on HW that doesn't have NV at all.
Fixes: da9af5071b25 ("arm64: cpufeature: Detect HCR_EL2.NV1 being RES0")
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
This patch in turn introduces the following warning during boot
(observed on today's linux-next):
CPU: All CPU(s) started at EL2
CPU features: detected: 32-bit EL0 Support
CPU features: detected: 32-bit EL1 Support
CPU features: detected: CRC32 instructions
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at arch/arm64/kernel/cpufeature.c:3369
this_cpu_has_cap+0x18/0x70
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.8.0-rc4-next-20240213 #8014
Hardware name: Khadas VIM3 (DT)
pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : this_cpu_has_cap+0x18/0x70
lr : has_nv1+0x24/0xcc
...
Call trace:
this_cpu_has_cap+0x18/0x70
update_cpu_capabilities+0x50/0x134
setup_system_features+0x30/0x120
smp_cpus_done+0x48/0xb4
smp_init+0x7c/0x8c
kernel_init_freeable+0x18c/0x4e4
kernel_init+0x20/0x1d8
ret_from_fork+0x10/0x20
irq event stamp: 2846
hardirqs last enabled at (2845): [<ffff80008012cf5c>]
console_unlock+0x164/0x190
hardirqs last disabled at (2846): [<ffff80008123a078>] el1_dbg+0x24/0x8c
softirqs last enabled at (2842): [<ffff800080010a60>]
__do_softirq+0x4a0/0x4e8
softirqs last disabled at (2827): [<ffff8000800169b0>]
____do_softirq+0x10/0x1c
---[ end trace 0000000000000000 ]---
alternatives: applying system-wide alternatives
This is nothing short of embarrassing. It looks like I somehow managed
to drop CONFIG_PREEMPT from my test config, making it impossible to
identify these issues. Apologies for that.
The following patch fixes it for me. Could you please give it a go?
Thanks,
M.
From cd75279d3b6c387c13972b61c486a203d9652e97 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <maz@xxxxxxxxxx>
Date: Tue, 13 Feb 2024 13:37:57 +0000
Subject: [PATCH] arm64: cpufeatures: Fix FEAT_NV check when checking for
FEAT_NV1
Using this_cpu_has_cap() has the potential to go wrong when
used system-wide on a preemptible kernel. Instead, use the
__system_matches_cap() helper when checking for FEAT_NV in the
FEAT_NV1 probing helper.
Fixes: 3673d01a2f55 ("arm64: cpufeatures: Only check for NV1 if NV is present")
Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
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 3421b684d340..f309fd542c20 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1812,7 +1812,7 @@ static bool has_nv1(const struct arm64_cpu_capabilities *entry, int scope)
{}
};
- return (this_cpu_has_cap(ARM64_HAS_NESTED_VIRT) &&
+ return (__system_matches_cap(ARM64_HAS_NESTED_VIRT) &&
Even though this change now uses SYSTEM scope for NESTED_VIRT, that is
the correct choice. Ideally, we should use the scope that was passed
into "has_v1", but as we have seen SCOPE_LOCAL is not safe. SYSTEM
schope works fine as both NV1 and NESTED_VIRT are SYSTEM scope. The only
time we run them SCOPE_LOCAL is for hotplugged in CPUs, at which point
the SYSTEM wide caps are finalized and will use the right value.
Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
!(has_cpuid_feature(entry, scope) ||
is_midr_in_range_list(read_cpuid_id(), nv1_ni_list)));
}
