On Tue, Feb 07 2023 at 19:53, David Woodhouse wrote: > On Tue, 2023-02-07 at 15:24 +0100, Thomas Gleixner wrote: > Thanks. I've reworked and I think I've caught everything. Didn't want > to elide the credit where Usama had done some of the forward-porting > work, so I've left those notes and the SoB intact on those patches, on > the assumption that they will be reposting the series after proper > testing on hardware again anyway (I'm only spawning it in qemu right > now). > > https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/parallel-6.2-rc7 > > The only real code change other than what we've discussed here is to > implement what we talked about for CPUID 0xb vs. 0x1 etc: > > /* > * We can do 64-bit AP bringup in parallel if the CPU reports > * its APIC ID in CPUID (either leaf 0x0B if we need the full > * APIC ID in X2APIC mode, or leaf 0x01 if 8 bits are > * sufficient). Otherwise it's too hard. And not for SEV-ES > * guests because they can't use CPUID that early. > */ > if (IS_ENABLED(CONFIG_X86_32) || boot_cpu_data.cpuid_level < 1 || > (x2apic_mode && boot_cpu_data.cpuid_level < 0xb) || > cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) > do_parallel_bringup = false; > > if (do_parallel_bringup && x2apic_mode) { > unsigned int eax, ebx, ecx, edx; > > /* > * To support parallel bringup in x2apic mode, the AP will need > * to obtain its APIC ID from CPUID 0x0B, since CPUID 0x01 has > * only 8 bits. Check that it is present and seems correct. > */ > cpuid_count(0xb, 0, &eax, &ebx, &ecx, &edx); > > /* > * AMD says that if executed with an umimplemented level in > * ECX, then it will return all zeroes in EAX. Intel says it > * will return zeroes in both EAX and EBX. Checking only EAX > * should be sufficient. > */ > if (eax) { > smpboot_control = STARTUP_SECONDARY | STARTUP_APICID_CPUID_0B; > } else { > pr_info("Disabling parallel bringup because CPUID 0xb looks untrustworthy\n"); > do_parallel_bringup = false; > } > } else if (do_parallel_bringup) { > /* Without X2APIC, what's in CPUID 0x01 should suffice. */ > smpboot_control = STARTUP_SECONDARY | STARTUP_APICID_CPUID_01; > } Looks good to me! Thanks, tglx
