Re: [PATCH v7 2/3] powerpc/powernv: Introduce a machine check hook for Guest MCEs.

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Apr 06, 2017 at 02:17:22AM +0530, Mahesh J Salgaonkar wrote:
> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> 
> This patch introduces a mce hook which is invoked at the time of guest
> exit to facilitate the host-side handling of machine check exception
> before the exception is passed on to the guest. This hook will be invoked
> from host virtual mode from KVM (before exiting the guest with
> KVM_EXIT_NMI reason) for machine check exception that occurs in the guest.
> 
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

Um.. this introduces the hook, and puts in an implementation of it,
but AFAICT, nothing calls it, either here or in the next patch.  That
seems a bit pointless.

> ---
>  arch/powerpc/include/asm/machdep.h     |    7 +++++++
>  arch/powerpc/include/asm/opal.h        |    4 ++++
>  arch/powerpc/platforms/powernv/opal.c  |   26 ++++++++++++++++++++++++++
>  arch/powerpc/platforms/powernv/setup.c |    3 +++
>  4 files changed, 40 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
> index 5011b69..9d74e7a 100644
> --- a/arch/powerpc/include/asm/machdep.h
> +++ b/arch/powerpc/include/asm/machdep.h
> @@ -15,6 +15,7 @@
>  #include <linux/export.h>
>  
>  #include <asm/setup.h>
> +#include <asm/mce.h>
>  
>  /* We export this macro for external modules like Alsa to know if
>   * ppc_md.feature_call is implemented or not
> @@ -112,6 +113,12 @@ struct machdep_calls {
>  	/* Called during machine check exception to retrive fixup address. */
>  	bool		(*mce_check_early_recovery)(struct pt_regs *regs);
>  
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> +	/* Called after KVM interrupt handler finishes handling MCE for guest */
> +	int		(*machine_check_exception_guest)
> +					(struct machine_check_event *evt);
> +#endif
> +
>  	/* Motherboard/chipset features. This is a kind of general purpose
>  	 * hook used to control some machine specific features (like reset
>  	 * lines, chip power control, etc...).
> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index 1ff03a6..9b1fcbf 100644
> --- a/arch/powerpc/include/asm/opal.h
> +++ b/arch/powerpc/include/asm/opal.h
> @@ -17,6 +17,7 @@
>  #ifndef __ASSEMBLY__
>  
>  #include <linux/notifier.h>
> +#include <asm/mce.h>
>  
>  /* We calculate number of sg entries based on PAGE_SIZE */
>  #define SG_ENTRIES_PER_NODE ((PAGE_SIZE - 16) / sizeof(struct opal_sg_entry))
> @@ -273,6 +274,9 @@ extern int opal_hmi_handler_init(void);
>  extern int opal_event_init(void);
>  
>  extern int opal_machine_check(struct pt_regs *regs);
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> +extern int opal_machine_check_guest(struct machine_check_event *evt);
> +#endif
>  extern bool opal_mce_check_early_recovery(struct pt_regs *regs);
>  extern int opal_hmi_exception_early(struct pt_regs *regs);
>  extern int opal_handle_hmi_exception(struct pt_regs *regs);
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index e0f856b..5e633a4 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -479,6 +479,32 @@ int opal_machine_check(struct pt_regs *regs)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> +/*
> + * opal_machine_check_guest() is a hook which is invoked at the time
> + * of guest exit to facilitate the host-side handling of machine check
> + * exception before the exception is passed on to the guest. This hook
> + * is invoked from host virtual mode from KVM (before exiting the guest
> + * with KVM_EXIT_NMI reason) for machine check exception that occurs in
> + * the guest.
> + *
> + * Currently no action is performed in the host other than printing the
> + * event information. The machine check exception is passed on to the
> + * guest kernel and the guest kernel will attempt for recovery.
> + */
> +int opal_machine_check_guest(struct machine_check_event *evt)
> +{
> +	/* Print things out */
> +	if (evt->version != MCE_V1) {
> +		pr_err("Machine Check Exception, Unknown event version %d !\n",
> +		       evt->version);
> +		return 0;
> +	}
> +	machine_check_print_event_info(evt);
> +	return 0;
> +}
> +#endif
> +
>  /* Early hmi handler called in real mode. */
>  int opal_hmi_exception_early(struct pt_regs *regs)
>  {
> diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
> index d50c7d9..333ee09 100644
> --- a/arch/powerpc/platforms/powernv/setup.c
> +++ b/arch/powerpc/platforms/powernv/setup.c
> @@ -264,6 +264,9 @@ static void __init pnv_setup_machdep_opal(void)
>  	ppc_md.mce_check_early_recovery = opal_mce_check_early_recovery;
>  	ppc_md.hmi_exception_early = opal_hmi_exception_early;
>  	ppc_md.handle_hmi_exception = opal_handle_hmi_exception;
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> +	ppc_md.machine_check_exception_guest = opal_machine_check_guest;
> +#endif
>  }
>  
>  static int __init pnv_probe(void)
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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