Subject: Re: [PATCH] Make system_reset_pSeries relocatable

From: Balbir Singh <[email-masked]>
Date: Wed, 27 Jul 2016 21:34:40 +1000

On Wed, Jul 27, 2016 at 05:32:06PM +1000, Balbir Singh wrote:
> 
> From: Balbir Singh <[email-masked]>
> 
> Currently the power management bits are broken w.r.t. relocation.
> There are direct branches from system_reset_pSeries to
> power7_wakeup_*. The correct way to do it is to do what
> the slb miss handler does, which is jump to a small stub within
> the first 64k of the relocated address and then jump to the
> actual location.
> 
> The code has been lightly tested (not the kvm bits), I would highly
> appreciate a review of the code. I suspect there might be easy
> to find bugs :)
>
Snip
 
> +	.align 7
> +_GLOBAL(power7_wakeup_common)
> +#ifdef CONFIG_RELOCATABLE
> +	mtctr	r11
> +#endif
> +	lbz	r0,PACA_THREAD_IDLE_STATE(r13)
> +	cmpwi   cr2,r0,PNV_THREAD_NAP
> +	bgt     cr2,8f				/* Either sleep or Winkle */
> +
> +	/* Waking up from nap should not cause hypervisor state loss */
> +	bgt	cr3,.
> +
> +	/* Waking up from nap */
> +	li	r0,PNV_THREAD_RUNNING
> +	stb	r0,PACA_THREAD_IDLE_STATE(r13)	/* Clear thread state */
> +
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> +	li	r0,KVM_HWTHREAD_IN_KERNEL
> +	stb	r0,HSTATE_HWTHREAD_STATE(r13)
> +	/* Order setting hwthread_state vs. testing hwthread_req */
> +	sync
> +	lbz	r0,HSTATE_HWTHREAD_REQ(r13)
> +	cmpwi	r0,0
> +	beq	1f
> +	b	kvm_start_guest
> +1:
> +#endif
> +
> +	/* Return SRR1 from power7_nap() */
> +	mfspr	r3,SPRN_SRR1
> +	beq	cr3,2f
> +	b	power7_wakeup_noloss
> +2:	b	power7_wakeup_loss
> +
> +	/* Fast Sleep wakeup on PowerNV */
> +8:	GET_PACA(r13)
> +	b 	power7_wakeup_tb_loss
> +
>  /*
>   * Hash table stuff
>   */

As per 0day, this part needs to be under #ifdef CONFIG_PPC_P7_NAP

I'll repose a new version tomorrow.

Balbir Singh