Re: [PATCH v12 13/16] arm64: kexec_file: invoke the kernel without purgatory
From: AKASHI Takahiro
Date: Fri Jul 27 2018 - 03:21:12 EST
On Thu, Jul 26, 2018 at 02:36:07PM +0100, James Morse wrote:
> Hi Akashi,
> On 24/07/18 07:57, AKASHI Takahiro wrote:
> > On arm64, purgatory would do almost nothing. So just invoke secondary
> > kernel directly by jumping into its entry code.
> > While, in this case, cpu_soft_restart() must be called with dtb address
> > in the fifth argument, the behavior still stays compatible with kexec_load
> > case as long as the argument is null.
> This patch conflicts with commit 76f4e2da45b4 ("arm64: kexec: always reset to
> EL2 if present") in the arm64 tree.
I haven't noticed Mark's patch.
I'm going to have to refresh my memory regarding why I introduced
el2_switch when I implemented kdump.
According to my current memory, however, I added
kvm_arch_hardware_enable/disable(), and associated functions, to gracefully
shutdown EL2 in case of kexec. Since we have no chance to call reset
function (via notifier) at kdump, I believed that el2_switch was necessary
for better chance of successful kdump.
> > diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
> > index f76ea92dff91..830a5063e09d 100644
> > --- a/arch/arm64/kernel/machine_kexec.c
> > +++ b/arch/arm64/kernel/machine_kexec.c
> > @@ -205,10 +205,18 @@ void machine_kexec(struct kimage *kimage)
> > * uses physical addressing to relocate the new image to its final
> > * position and transfers control to the image entry point when the
> > * relocation is complete.
> > + * In kexec case, kimage->start points to purgatory assuming that
> > + * kernel entry and dtb address are embedded in purgatory by
> > + * userspace (kexec-tools).
> > + * In kexec_file case, the kernel starts directly without purgatory.
> > */
> > -
> > cpu_soft_restart(kimage != kexec_crash_image,
> > - reboot_code_buffer_phys, kimage->head, kimage->start, 0);
> > + reboot_code_buffer_phys, kimage->head, kimage->start,
> > +#ifdef CONFIG_KEXEC_FILE
> > + kimage->arch.dtb_mem);
> > +#else
> > + 0);
> > +#endif
> > BUG(); /* Should never get here. */
> > }