Messages in this thread | | | Date | Wed, 25 Mar 2020 03:17:24 -0700 | Subject | Re: [PATCH] x86/smpboot: Remove 486-isms from the modern AP boot path | From | hpa@zytor ... |
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On March 25, 2020 3:14:31 AM PDT, Andrew Cooper <andrew.cooper3@citrix.com> wrote: >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 <tglx@linutronix.de> >CC: Ingo Molnar <mingo@redhat.com> >CC: Borislav Petkov <bp@alien8.de> >CC: "H. Peter Anvin" <hpa@zytor.com> >CC: x86@kernel.org >CC: Jan Kiszka <jan.kiszka@siemens.com> >CC: James Morris <jmorris@namei.org> >CC: David Howells <dhowells@redhat.com> >CC: Andrew Cooper <andrew.cooper3@citrix.com> >CC: Matthew Garrett <mjg59@google.com> >CC: Josh Boyer <jwboyer@redhat.com> >CC: Zhenzhong Duan <zhenzhong.duan@oracle.com> >CC: Steve Wahl <steve.wahl@hpe.com> >CC: Mike Travis <mike.travis@hpe.com> >CC: Dimitri Sivanich <dimitri.sivanich@hpe.com> >CC: Arnd Bergmann <arnd@arndb.de> >CC: "Peter Zijlstra (Intel)" <peterz@infradead.org> >CC: Giovanni Gherdovich <ggherdovich@suse.cz> >CC: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> >CC: Len Brown <len.brown@intel.com> >CC: Kees Cook <keescook@chromium.org> >CC: Martin Molnar <martin.molnar.programming@gmail.com> >CC: Pingfan Liu <kernelfans@gmail.com> >CC: linux-kernel@vger.kernel.org >CC: jailhouse-dev@googlegroups.com >Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> >--- >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... > */
We don't support SMP on 486 and haven't for a very long time. Is there any reason to retain that code at all? -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
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