On Fri, May 25, 2018 at 11:03:59AM +0100, Russell King - ARM Linux wrote: > On Thu, May 24, 2018 at 04:30:40PM -0700, Florian Fainelli wrote: > > On 05/21/2018 04:44 AM, Russell King wrote: > > > Check for CPU bugs when secondary processors are being brought online, > > > and also when CPUs are resuming from a low power mode. This gives an > > > opportunity to check that processor specific bug workarounds are > > > correctly enabled for all paths that a CPU re-enters the kernel. > > > > > > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> > > > Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx> > > > > Something I missed, is that this correctly warns about e.g: missing the > > IBE bit for secondary cores, but it seems to be missing it for the boot CPU: > > Are you sure that the boot CPU has the IBE bit clear? Here's what I get on TI Keystone 2, which doesn't set the IBE bit for any CPU: CPU: Testing write buffer coherency: ok CPU0: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable CPU0: Spectre v2: using ICIALLU workaround /cpus/cpu@0 missing clock-frequency property /cpus/cpu@1 missing clock-frequency property /cpus/cpu@2 missing clock-frequency property /cpus/cpu@3 missing clock-frequency property CPU0: thread -1, cpu 0, socket 0, mpidr 80000000 Setting up static identity map for 0x80008300 - 0x80008438 Hierarchical SRCU implementation. smp: Bringing up secondary CPUs ... CPU1: thread -1, cpu 1, socket 0, mpidr 80000001 CPU1: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable CPU1: Spectre v2: using ICIALLU workaround CPU2: thread -1, cpu 2, socket 0, mpidr 80000002 CPU2: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable CPU2: Spectre v2: using ICIALLU workaround CPU3: thread -1, cpu 3, socket 0, mpidr 80000003 CPU3: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable CPU3: Spectre v2: using ICIALLU workaround It should be noted that, if we implement a "bugs" bit exported to userspace (as I think someone requested) that booting on a system where only the boot CPU initially comes up (which has the IBE bit set) and then bringing the secondary CPUs online after userspace has started (where those CPUs don't have the IBE bit set) will result in the system initially not being vulnerable, but then becoming vulnerable when running on those other CPUs. If the bugs bit had already been checked by userspace, then it would think that there's no system level vulnerability. Userspace would need to check the status each time a CPU comes online. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
