Hi Stefano,
On 05/24/2018 01:48 AM, Stefano Stabellini wrote:
On Wed, 23 May 2018, Stefano Stabellini wrote:
On Tue, 22 May 2018, Julien Grall wrote:
+
+ default:
+ ASSERT_UNREACHABLE();
+ return false;
+ }
+
+ switch ( ssbd_state )
+ {
+ case ARM_SSBD_FORCE_DISABLE:
+ {
+ static bool once = true;
+
+ if ( once )
+ printk("%s disabled from command-line\n", entry->desc);
+ once = false;
+
+ arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_2_FID, 0, NULL);
+ required = false;
+
+ break;
+ }
+
+ case ARM_SSBD_RUNTIME:
+ if ( required )
+ {
+ this_cpu(ssbd_callback_required) = 1;
We have the ARM_SSBD bit, the ssbd_state variable and
ssbd_callback_required. Both ARM_SSBD and ssbd_state are shared across
cores while ssbd_callback_required is per-cpu. Does
ssbd_callback_required really need to be per-cpu? Do we need both
variables? For instance, we could just return ssbd_state ==
ARM_SSBD_RUNTIME instead of this_cpu(ssbd_callback_required)?
After reading the whole series, I think ssbd_state should be a per_cpu
variable. parse_spec_ctrl initializes ssbd_state to the same value on
all cpus. has_ssbd_mitigation modifies ssbd_state only on the CPUs it is
running on. We get rid of ssbd_callback_required. The assembly fast past
reads ssbd_state instead of ssbd_callback_required.
What do you think?
We need to keep the global ssbd_state around for the vsmc code as we
need to tell the guest what is the system-wide decision.
This is because a vCPU may move from a affected CPU to a non-affected
one. So we need to inform the same on every vCPU (i.e mitigated,
dynamic...).
Cheers,
--
Julien Grall
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