Re: [PATCH v2] kexec: Fix kdump failure with notsc

[Baoquan He]

On 07/12/16 at 02:52pm, Xunlei Pang wrote:
> On 2016/07/07 at 18:17, Wei Jiangang wrote:
> > Signed-off-by: Wei Jiangang <weijg.fnst@xxxxxxxxxxxxxx>
> > ---
> > +/* Local APIC is disabled by the kernel for crash or reboot path */
> > +static int disabled_local_apic;
> > +
> >  /*
> >   * Knob to control our willingness to enable the local APIC.
> >   *
> > @@ -1097,10 +1100,16 @@ void lapic_shutdown(void)
> >  #endif
> >  		disable_local_APIC();
> >  
> > +	disabled_local_apic = 1;
> >  
> >  	local_irq_restore(flags);
> >  }
> >  
> > +int lapic_disabled(void)
> > +{
> > +	return disabled_local_apic;
> > +}
> > +
> >  /**
> >   * sync_Arb_IDs - synchronize APIC bus arbitration IDs
> >   */
> > diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
> > index 469b23d6acc2..c934a7868e6b 100644
> > --- a/arch/x86/kernel/machine_kexec_32.c
> > +++ b/arch/x86/kernel/machine_kexec_32.c
> > @@ -202,14 +202,13 @@ void machine_kexec(struct kimage *image)
> >  	local_irq_disable();
> >  	hw_breakpoint_disable();
> >  
> > -	if (image->preserve_context) {
> > +	if (image->preserve_context || lapic_disabled()) {
> >  #ifdef CONFIG_X86_IO_APIC
> >  		/*
> >  		 * We need to put APICs in legacy mode so that we can
> >  		 * get timer interrupts in second kernel. kexec/kdump
> >  		 * paths already have calls to disable_IO_APIC() in
> > -		 * one form or other. kexec jump path also need
> > -		 * one.
> > +		 * one form or other. kexec jump path also need one.
> >  		 */
> >  		disable_IO_APIC();
> 
> Hi Wei,
> 
> As the comment says, kexec/kdump paths already have disable_IO_APIC(), why again here?

I also have this question. I guess Jiangang didn't post his modification
correctly. He should remove calling of disable_IO_APIC in
native_machine_crash_shutdown(). Assume his test was done on correct
code change. 

> 
> Regards,
> Xunlei
> 
> >  #endif
> > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> > index 5a294e48b185..d3598cdd6437 100644
> > --- a/arch/x86/kernel/machine_kexec_64.c
> > +++ b/arch/x86/kernel/machine_kexec_64.c
> > @@ -23,6 +23,7 @@
> >  #include <asm/pgtable.h>
> >  #include <asm/tlbflush.h>
> >  #include <asm/mmu_context.h>
> > +#include <asm/apic.h>
> >  #include <asm/io_apic.h>
> >  #include <asm/debugreg.h>
> >  #include <asm/kexec-bzimage64.h>
> > @@ -269,14 +270,13 @@ void machine_kexec(struct kimage *image)
> >  	local_irq_disable();
> >  	hw_breakpoint_disable();
> >  
> > -	if (image->preserve_context) {
> > +	if (image->preserve_context || lapic_disabled()) {
> >  #ifdef CONFIG_X86_IO_APIC
> >  		/*
> >  		 * We need to put APICs in legacy mode so that we can
> >  		 * get timer interrupts in second kernel. kexec/kdump
> >  		 * paths already have calls to disable_IO_APIC() in
> > -		 * one form or other. kexec jump path also need
> > -		 * one.
> > +		 * one form or other. kexec jump path also need one.
> >  		 */
> >  		disable_IO_APIC();
> >  #endif
> 
> 
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