Linux has an implementation of the Universal Start-up Algorithm (MP spec, Appendix B.4, Application Processor Startup), which includes unconditionally writing to the Bios Data Area and CMOS registers.
The warm reset vector is only necessary in the non-integrated Local APIC case. UV and Jailhouse already have an opt-out for this behaviour, but blindly using the BDA and CMOS on a UEFI or other reduced hardware system isn't clever. Drop the warm_reset flag from struct x86_legacy_features, and tie the warm vector modifications to the integrated-ness of the Local APIC. This has the advantage of compiling the warm reset logic out entirely for 64bit builds. CC: Thomas Gleixner <[email protected]> CC: Ingo Molnar <[email protected]> CC: Borislav Petkov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: [email protected] CC: Jan Kiszka <[email protected]> CC: James Morris <[email protected]> CC: David Howells <[email protected]> CC: Andrew Cooper <[email protected]> CC: Matthew Garrett <[email protected]> CC: Josh Boyer <[email protected]> CC: Zhenzhong Duan <[email protected]> CC: Steve Wahl <[email protected]> CC: Mike Travis <[email protected]> CC: Dimitri Sivanich <[email protected]> CC: Arnd Bergmann <[email protected]> CC: "Peter Zijlstra (Intel)" <[email protected]> CC: Giovanni Gherdovich <[email protected]> CC: "Rafael J. Wysocki" <[email protected]> CC: Len Brown <[email protected]> CC: Kees Cook <[email protected]> CC: Martin Molnar <[email protected]> CC: Pingfan Liu <[email protected]> CC: [email protected] CC: [email protected] Signed-off-by: Andrew Cooper <[email protected]> --- Thomas: I finally found the reference we were discussing in Portland. Sorry this patch took so long. I don't have any non-integrated APIC hardware to test with. Can anyone help me out? --- arch/x86/include/asm/x86_init.h | 1 - arch/x86/kernel/apic/x2apic_uv_x.c | 1 - arch/x86/kernel/jailhouse.c | 1 - arch/x86/kernel/platform-quirks.c | 1 - arch/x86/kernel/smpboot.c | 21 ++++++++++++--------- 5 files changed, 12 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h index 96d9cd208610..006a5d7fd7eb 100644 --- a/arch/x86/include/asm/x86_init.h +++ b/arch/x86/include/asm/x86_init.h @@ -229,7 +229,6 @@ enum x86_legacy_i8042_state { struct x86_legacy_features { enum x86_legacy_i8042_state i8042; int rtc; - int warm_reset; int no_vga; int reserve_bios_regions; struct x86_legacy_devices devices; diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c index ad53b2abc859..5afcfd193592 100644 --- a/arch/x86/kernel/apic/x2apic_uv_x.c +++ b/arch/x86/kernel/apic/x2apic_uv_x.c @@ -343,7 +343,6 @@ static int __init uv_acpi_madt_oem_check(char *_oem_id, char *_oem_table_id) } else if (!strcmp(oem_table_id, "UVH")) { /* Only UV1 systems: */ uv_system_type = UV_NON_UNIQUE_APIC; - x86_platform.legacy.warm_reset = 0; __this_cpu_write(x2apic_extra_bits, pnodeid << uvh_apicid.s.pnode_shift); uv_set_apicid_hibit(); uv_apic = 1; diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c index 6eb8b50ea07e..d628fe92d6af 100644 --- a/arch/x86/kernel/jailhouse.c +++ b/arch/x86/kernel/jailhouse.c @@ -210,7 +210,6 @@ static void __init jailhouse_init_platform(void) x86_platform.calibrate_tsc = jailhouse_get_tsc; x86_platform.get_wallclock = jailhouse_get_wallclock; x86_platform.legacy.rtc = 0; - x86_platform.legacy.warm_reset = 0; x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT; legacy_pic = &null_legacy_pic; diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c index b348a672f71d..d922c5e0c678 100644 --- a/arch/x86/kernel/platform-quirks.c +++ b/arch/x86/kernel/platform-quirks.c @@ -9,7 +9,6 @@ void __init x86_early_init_platform_quirks(void) { x86_platform.legacy.i8042 = X86_LEGACY_I8042_EXPECTED_PRESENT; x86_platform.legacy.rtc = 1; - x86_platform.legacy.warm_reset = 1; x86_platform.legacy.reserve_bios_regions = 0; x86_platform.legacy.devices.pnpbios = 1; diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index d85e91a8aa8c..e2ebb0be2ee3 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1049,18 +1049,21 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle, * the targeted processor. */ - if (x86_platform.legacy.warm_reset) { + /* + * APs are typically started in one of two ways: + * + * - On 486-era hardware with a non-integrated Local APIC, a single + * INIT IPI is sent. When the AP comes out of reset, the BIOS + * follows the warm reset vector to start_ip. + * - On everything with an integrated Local APIC, the start_ip is + * provided in the Startup IPI message, sent as part of an + * INIT-SIPI-SIPI sequence. + */ + if (!APIC_INTEGRATED(boot_cpu_apic_version)) { pr_debug("Setting warm reset code and vector.\n"); smpboot_setup_warm_reset_vector(start_ip); - /* - * Be paranoid about clearing APIC errors. - */ - if (APIC_INTEGRATED(boot_cpu_apic_version)) { - apic_write(APIC_ESR, 0); - apic_read(APIC_ESR); - } } /* @@ -1118,7 +1121,7 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle, } } - if (x86_platform.legacy.warm_reset) { + if (!APIC_INTEGRATED(boot_cpu_apic_version)) { /* * Cleanup possible dangling ends... */ -- 2.11.0 -- You received this message because you are subscribed to the Google Groups "Jailhouse" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/jailhouse-dev/20200325101431.12341-1-andrew.cooper3%40citrix.com.
