Sean Christopherson <seanjc@xxxxxxxxxx> writes: > On Tue, Aug 02, 2022, Vitaly Kuznetsov wrote: >> While it seems reasonable to not expose LOAD_IA32_PERF_GLOBAL_CTRL controls >> to L1 hypervisor on buggy CPUs, such change would inevitably break live >> migration from older KVMs where the controls are exposed. Keep the status quo >> for now, L1 hypervisor itself is supposed to take care of the errata. > > As noted before, this statement is wrong as it requires guest FMS == host FMS, > but it's irrelevant because KVM can emulate the control unconditionally. I'll > test and fold in my suggested patch[*] (assuming it works) and reword this part > of the changelog. Ah, and I'll also need to fold in a patch to actually emulate > the controls without hardware support. > > [*] https://lore.kernel.org/all/YtnZmCutdd5tpUmz@xxxxxxxxxx Oh, I missed the part that my changelog is actually wrong when Paolo said "Can you send this as a separate patch", no objections to re-wording! > >> Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> >> --- >> arch/x86/kvm/vmx/vmx.c | 59 +++++++++++++++++++++++++----------------- >> 1 file changed, 35 insertions(+), 24 deletions(-) >> > > ... > >> @@ -8192,6 +8199,10 @@ static __init int hardware_setup(void) >> if (setup_vmcs_config(&vmcs_config, &vmx_capability) < 0) >> return -EIO; >> >> + if (cpu_has_perf_global_ctrl_bug()) >> + pr_warn_once("kvm: VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL " >> + "does not work properly. Using workaround\n"); > > Any objections to opportunistically tweaking this? > > pr_warn_once("kvm: CPU has VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL erratum," > "using MSR load/store lists for PERF_GLOBAL_CTRL\n"); > Personally I'd say just pr_warn_once("kvm: CPU has VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL erratum\n"); leaving aside the workaround KVM uses. This is merely an implementation detail which KVM users most likely don't really need. I have no strong opinion though, feel free to adjust. >> + >> if (boot_cpu_has(X86_FEATURE_NX)) >> kvm_enable_efer_bits(EFER_NX); >> >> -- >> 2.35.3 >> > -- Vitaly
