The logic to detect whether there's a change in the previous and next task's flag relevant to update speculation control MSRs are spread out across multiple functions.
Consolidate all checks needed for updating speculation control MSRs to __speculation_ctrl_update().
This makes it easy to pick the right speculation control MSR, and the bits in the MSR that needs updating based on TIF flags changes.
Originally-by: Thomas Lendacky Thomas.Lendacky@amd.com Signed-off-by: Tim Chen tim.c.chen@linux.intel.com --- arch/x86/kernel/process.c | 44 +++++++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 8aa4960..74bef48 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -397,25 +397,48 @@ static __always_inline void amd_set_ssb_virt_state(unsigned long tifn)
static __always_inline void spec_ctrl_update_msr(unsigned long tifn) { - u64 msr = x86_spec_ctrl_base | ssbd_tif_to_spec_ctrl(tifn); + u64 msr = x86_spec_ctrl_base; + + /* + * If X86_FEATURE_SSBD is not set, the SSBD + * bit is not to be touched. + */ + if (static_cpu_has(X86_FEATURE_SSBD)) + msr |= ssbd_tif_to_spec_ctrl(tifn);
wrmsrl(MSR_IA32_SPEC_CTRL, msr); }
-static __always_inline void __speculation_ctrl_update(unsigned long tifn) -{ - if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) - amd_set_ssb_virt_state(tifn); - else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) - amd_set_core_ssb_state(tifn); - else +/* + * Update the MSRs managing speculation control during context switch. + * + * tifp: previous task's thread flags + * tifn: next task's thread flags + */ +static __always_inline void __speculation_ctrl_update(unsigned long tifp, + unsigned long tifn) +{ + bool updmsr = false; + + /* If TIF_SSBD is different, select the proper mitigation method */ + if ((tifp ^ tifn) & _TIF_SSBD) { + if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) + amd_set_ssb_virt_state(tifn); + else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) + amd_set_core_ssb_state(tifn); + else if (static_cpu_has(X86_FEATURE_SSBD)) + updmsr = true; + } + + if (updmsr) spec_ctrl_update_msr(tifn); }
void speculation_ctrl_update(unsigned long tif) { + /* Forced update. Make sure all relevant TIF flags are different */ preempt_disable(); - __speculation_ctrl_update(tif); + __speculation_ctrl_update(~tif, tif); preempt_enable(); }
@@ -451,8 +474,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, if ((tifp ^ tifn) & _TIF_NOCPUID) set_cpuid_faulting(!!(tifn & _TIF_NOCPUID));
- if ((tifp ^ tifn) & _TIF_SSBD) - __speculation_ctrl_update(tifn); + __speculation_ctrl_update(tifp, tifn); }
/*