This change adds a new kernel configuration that sets the l1d cache flush setting at compile time rather than at run time. The reasons for this change are as follows - - Kernel command line arguments are getting unwieldy. These parameters are not a scalable way to set the kernel config. They're intended as a super limited way for the bootloader to pass info to the kernel and also as a way for end users who are not compiling the kernel themselves to tweak the kernel behavior. - Also, if a user wants this setting from the start. It's a definite smell that it deserves to be a compile time thing rather than adding extra code plus whatever miniscule time at runtime to pass an extra argument. - Finally, it doesn't preclude the runtime / kernel command line way. Users are free to use those as well. Signed-off-by: Abhishek Bhardwaj <abhishekbh@xxxxxxxxxx> --- Changes in v4: - Add motivation for the change in the commit message. Changes in v3: - Change depends on to only x86_64. - Remove copy paste errors at the end of the KConfig. Changes in v2: - Fix typo in the help of the new KConfig. arch/x86/kernel/cpu/bugs.c | 8 ++++++++ arch/x86/kvm/Kconfig | 13 +++++++++++++ 2 files changed, 21 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 0b71970d2d3d2..1dcc875cf5547 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1406,7 +1406,15 @@ enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH; #if IS_ENABLED(CONFIG_KVM_INTEL) EXPORT_SYMBOL_GPL(l1tf_mitigation); #endif +#if (CONFIG_KVM_VMENTRY_L1D_FLUSH == 1) +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NEVER; +#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 2) +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_COND; +#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 3) +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_ALWAYS; +#else enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO; +#endif EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation); /* diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index b277a2db62676..1f85374a0b812 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -107,4 +107,17 @@ config KVM_MMU_AUDIT This option adds a R/W kVM module parameter 'mmu_audit', which allows auditing of KVM MMU events at runtime. +config KVM_VMENTRY_L1D_FLUSH + int "L1D cache flush settings (1-3)" + range 1 3 + default "2" + depends on KVM && X86_64 + help + This setting determines the L1D cache flush behavior before a VMENTER. + This is similar to setting the option / parameter to + kvm-intel.vmentry_l1d_flush. + 1 - Never flush. + 2 - Conditionally flush. + 3 - Always flush. + endif # VIRTUALIZATION -- 2.27.0.383.g050319c2ae-goog
