FAILED: patch "[PATCH] x86/crash: Disable virt in core NMI crash handler to avoid" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 26044aff37a5455b19a91785086914fd33053ef4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '[email protected]' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

26044aff37a5 ("x86/crash: Disable virt in core NMI crash handler to avoid double shootdown") ed72736183c4 ("x86/reboot: Force all cpus to exit VMX root if VMX is supported") 4d1d0977a215 ("x86: Fix a handful of typos")
22ca7ee933a3 ("x86/apic: Provide and use helper for send_IPI_allbutself()")
6a1cb5f5c641 ("x86/apic: Add static key to Control IPI shorthands")
bdda3b93e660 ("x86/apic: Move no_ipi_broadcast() out of 32bit")
9c92374b631d ("x86/cpu: Move arch_smt_update() to a neutral place")
c94f0718fb1c ("x86/apic: Consolidate the apic local headers")
ba77b2a02e00 ("x86/apic: Move apic_flat_64 header into apic directory")
8b542da37287 ("x86/apic: Move ipi header into apic directory")
521b82fee98c ("x86/apic: Cleanup the include maze")
cdc86c9d1f82 ("x86/apic: Move IPI inlines into ipi.c")
2591bc4e8d70 ("x86/kgbd: Use NMI_VECTOR not APIC_DM_NMI")
747d5a1bf293 ("x86/reboot: Always use NMI fallback when shutdown via reboot vector IPI fails") 7e300dabb7e7 ("treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 223") fa4bff165070 ("Merge branch 'x86-mds-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 26044aff37a5455b19a91785086914fd33053ef4 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <[email protected]>
Date: Wed, 30 Nov 2022 23:36:47 +0000
Subject: [PATCH] x86/crash: Disable virt in core NMI crash handler to avoid
double shootdown

Disable virtualization in crash_nmi_callback() and rework the emergency_vmx_disable_all() path to do an NMI shootdown if and only if a
shootdown has not already occurred. NMI crash shootdown fundamentally
can't support multiple invocations as responding CPUs are deliberately put into halt state without unblocking NMIs. But, the emergency reboot path doesn't have any work of its own, it simply cares about disabling virtualization, i.e. so long as a shootdown occurred, emergency reboot doesn't care who initiated the shootdown, or when.

If "crash_kexec_post_notifiers" is specified on the kernel command line, panic() will invoke crash_smp_send_stop() and result in a second call to nmi_shootdown_cpus() during native_machine_emergency_restart().

Invoke the callback _before_ disabling virtualization, as the current VMCS needs to be cleared before doing VMXOFF. Note, this results in a subtle change in ordering between disabling virtualization and stopping Intel PT on the responding CPUs. While VMX and Intel PT do interact, VMXOFF and writes to MSR_IA32_RTIT_CTL do not induce faults between one another, which is all that matters when panicking.

Harden nmi_shootdown_cpus() against multiple invocations to try and capture any such kernel bugs via a WARN instead of hanging the system during a crash/dump, e.g. prior to the recent hardening of register_nmi_handler(), re-registering the NMI handler would trigger a double list_add() and hang the system if CONFIG_BUG_ON_DATA_CORRUPTION=y.

list_add double add: new=ffffffff82220800, prev=ffffffff8221cfe8, next=ffffffff82220800.

 WARNING: CPU: 2 PID: 1319 at lib/list_debug.c:29 __list_add_valid+0x67/0x70
 Call Trace:
  __register_nmi_handler+0xcf/0x130
  nmi_shootdown_cpus+0x39/0x90
  native_machine_emergency_restart+0x1c9/0x1d0
  panic+0x237/0x29b

Extract the disabling logic to a common helper to deduplicate code, and to prepare for doing the shootdown in the emergency reboot path if SVM is supported.

Note, prior to commit ed72736183c4 ("x86/reboot: Force all cpus to exit VMX root if VMX is supported"), nmi_shootdown_cpus() was subtly protected against a second invocation by a cpu_vmx_enabled() check as the kdump handler would disable VMX if it ran first.

index 04c17be9b5fd..bc5b4d788c08 100644
@@ -25,6 +25,8 @@ void __noreturn machine_real_restart(unsigned int type);
 #define MRR_BIOS	0
 #define MRR_APM		1
 
+void cpu_emergency_disable_virtualization(void);
+
 typedef void (*nmi_shootdown_cb)(int, struct pt_regs*);
 void nmi_panic_self_stop(struct pt_regs *regs);
 void nmi_shootdown_cpus(nmi_shootdown_cb callback);

index 305514431f26..cdd92ab43cda 100644
@@ -37,7 +37,6 @@
 #include <linux/kdebug.h>
 #include <asm/cpu.h>
 #include <asm/reboot.h>
-#include <asm/virtext.h>
 #include <asm/intel_pt.h>
 #include <asm/crash.h>
 #include <asm/cmdline.h>

@@ -81,15 +80,6 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
 	 */
 	cpu_crash_vmclear_loaded_vmcss();
 
-	/* Disable VMX or SVM if needed.
-	 *
-	 * We need to disable virtualization on all CPUs.
-	 * Having VMX or SVM enabled on any CPU may break rebooting
-	 * after the kdump kernel has finished its task.
-	 */
-	cpu_emergency_vmxoff();
-	cpu_emergency_svm_disable();
-
 	/*
 	 * Disable Intel PT to stop its logging
 	 */

@@ -148,12 +138,7 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 	 */
 	cpu_crash_vmclear_loaded_vmcss();
 
-	/* Booting kdump kernel with VMX or SVM enabled won't work,
-	 * because (among other limitations) we can't disable paging
-	 * with the virt flags.
-	 */
-	cpu_emergency_vmxoff();
-	cpu_emergency_svm_disable();
+	cpu_emergency_disable_virtualization();
 
 	/*
 	 * Disable Intel PT to stop its logging