linux-kernel - Re: [PATCH linux-next v3 06/14] x86, crash: wrap crash dumping code into crash related ifdefs

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Date: Thu, 25 Jan 2024 12:09:36 +0800
From: Baoquan He <bhe@...hat.com>
To: Michael Kelley <mhklinux@...look.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	"linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"loongarch@...ts.linux.dev" <loongarch@...ts.linux.dev>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	"hbathini@...ux.ibm.com" <hbathini@...ux.ibm.com>,
	"piliu@...hat.com" <piliu@...hat.com>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Subject: Re: [PATCH linux-next v3 06/14] x86, crash: wrap crash dumping code
 into crash related ifdefs

On 01/24/24 at 11:02pm, Michael Kelley wrote:
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c
> > b/arch/x86/kernel/cpu/mshyperv.c
> > index 01fa06dd06b6..f8163a59026b 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -210,6 +210,7 @@ static void hv_machine_shutdown(void)
> >  		hyperv_cleanup();
> >  }
> > 
> > +#ifdef CONFIG_CRASH_DUMP
> >  static void hv_machine_crash_shutdown(struct pt_regs *regs)
> >  {
> >  	if (hv_crash_handler)
> > @@ -221,6 +222,7 @@ static void hv_machine_crash_shutdown(struct
> > pt_regs *regs)
> >  	/* Disable the hypercall page when there is only 1 active CPU. */
> >  	hyperv_cleanup();
> >  }
> > +#endif
> >  #endif /* CONFIG_KEXEC_CORE */
> 
> Note that the #ifdef CONFIG_CRASH_DUMP is nested inside
> #ifdef CONFIG_KEXEC_CODE here, and in the other Hyper-V code
> just below.   It's also nested in xen_hvm_guest_init() at the bottom
> of this patch.  But the KVM case of setting crash_shutdown is
> not nested -- you changed #ifdef CONFIG_KEXEC_CORE to #ifdef
> CONFIG_CRASH_DUMP.
> 
> I think both approaches work because CONFIG_CRASH_DUMP implies
> CONFIG_KEXEC_CORE, but I wonder if it would be better to *not* nest
> in all cases.  I'd like to see the cases be consistent so in the future
> someone doesn't wonder why there's a difference (unless there's
> a reason for the difference that I missed).

I agree with you, it's a great suggestion. Thanks.

Do you think below draft patch includes all changes you are concerned
about?

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index f8163a59026b..2e8cd5a4ae85 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -209,6 +209,7 @@ static void hv_machine_shutdown(void)
 	if (kexec_in_progress)
 		hyperv_cleanup();
 }
+#endif /* CONFIG_KEXEC_CORE */
 
 #ifdef CONFIG_CRASH_DUMP
 static void hv_machine_crash_shutdown(struct pt_regs *regs)
@@ -222,8 +223,7 @@ static void hv_machine_crash_shutdown(struct pt_regs *regs)
 	/* Disable the hypercall page when there is only 1 active CPU. */
 	hyperv_cleanup();
 }
-#endif
-#endif /* CONFIG_KEXEC_CORE */
+#endif /* CONFIG_CRASH_DUMP */
 #endif /* CONFIG_HYPERV */
 
 static uint32_t  __init ms_hyperv_platform(void)
@@ -497,9 +497,11 @@ static void __init ms_hyperv_init_platform(void)
 	no_timer_check = 1;
 #endif
 
-#if IS_ENABLED(CONFIG_HYPERV) && defined(CONFIG_KEXEC_CORE)
+#if IS_ENABLED(CONFIG_HYPERV)
+#if defined(CONFIG_KEXEC_CORE)
 	machine_ops.shutdown = hv_machine_shutdown;
-#ifdef CONFIG_CRASH_DUMP
+#endif
+#if defined(CONFIG_CRASH_DUMP)
 	machine_ops.crash_shutdown = hv_machine_crash_shutdown;
 #endif
 #endif
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 1287b0d5962f..f3130f762784 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -826,7 +826,7 @@ void machine_halt(void)
 	machine_ops.halt();
 }
 
-#ifdef CONFIG_KEXEC_CORE
+#ifdef CONFIG_CRASH_DUMP
 void machine_crash_shutdown(struct pt_regs *regs)
 {
 	machine_ops.crash_shutdown(regs);