Re: [PATCH 1/6] ARM: spectre-bhb: enable for Cortex-A15

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On 24/05/2022 18:03, Russell King (Oracle) wrote:
On Tue, May 24, 2022 at 03:50:17PM +0100, Jon Hunter wrote:
Hi Ard,

On 28/03/2022 14:47, Ard Biesheuvel wrote:
The Spectre-BHB mitigations were inadvertently left disabled for
Cortex-A15, due to the fact that cpu_v7_bugs_init() is not called in
that case. So fix that.

Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
   arch/arm/mm/proc-v7-bugs.c | 1 +
   1 file changed, 1 insertion(+)

diff --git a/arch/arm/mm/proc-v7-bugs.c b/arch/arm/mm/proc-v7-bugs.c
index 06dbfb968182..fb9f3eb6bf48 100644
--- a/arch/arm/mm/proc-v7-bugs.c
+++ b/arch/arm/mm/proc-v7-bugs.c
@@ -288,6 +288,7 @@ void cpu_v7_ca15_ibe(void)
   {
   	if (check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(0)))
   		cpu_v7_spectre_v2_init();
+	cpu_v7_spectre_bhb_init();
   }
   void cpu_v7_bugs_init(void)


Since this patch has been merged, I am seeing a ton of messages when booting
Linux on tegra124-jetson-tk1 ...

[ 1233.327547] CPU0: Spectre BHB: using loop workaround
[ 1233.327795] CPU1: Spectre BHB: using loop workaround
[ 1233.328270] CPU1: Spectre BHB: using loop workaround

Now that you mention this, I vaguely remember some email on the list a
while ago about this being caused by something like cpuidle - but I'm
unable to find it now.

[0] https://lore.kernel.org/linux-arm-kernel/20220519161310.1489625-1-dmitry.osipenko@xxxxxxxxxxxxx/T/

That was probably it.

We can't really do this for the other print, because the system status
can change as a result of CPUs being brought online. :(


Does it make sense to only print the message if/when the method changes as opposed to every time the CPUs are brought online? That way, there would still be at least one print showing the current method. I believe that is what Ard had proposed.

Jon

--
nvpublic



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