On Tue, Jan 25, 2022 at 11:27:55AM +0000, Marc Zyngier wrote:
Mark Brown broonie@kernel.org wrote:
- if (IS_ENABLED(CONFIG_ARM64_SME) && cpus_have_final_cap(ARM64_SME))
Please drop the IS_ENABLED(). We purposely avoid conditional compilation in KVM in order to avoid bitrot, and the amount of code you save isn't significant. Having a static key is more than enough to avoid runtime costs.
Sure, I wanted to be extra careful here as this is all in hot paths and going to get moved elsewhere when we have real guest support.
- if (IS_ENABLED(CONFIG_ARM64_SME) && cpus_have_final_cap(ARM64_SME) &&
cpus_have_final_cap(ARM64_HAS_FGT)) {val = read_sysreg_s(SYS_HFGRTR_EL2);val &= ~(HFGxTR_EL2_nTPIDR_EL0_MASK |HFGxTR_EL2_nSMPRI_EL1_MASK);write_sysreg_s(val, SYS_HFGRTR_EL2);val = read_sysreg_s(SYS_HFGWTR_EL2);val &= ~(HFGxTR_EL2_nTPIDR_EL0_MASK |HFGxTR_EL2_nSMPRI_EL1_MASK);write_sysreg_s(val, SYS_HFGWTR_EL2);- }
If the CPUs do not have FGT, what provides the equivalent trapping?
Nothing for nVHE mode.
If FGT is mandatory when SME exists, then you should simplify the condition.
OK, I'll remove the defensiveness here. FGT is mandatory from v8.6 and SME is a v9 feature so people shouldn't build a SME implementation that lacks FGT.