linux-kernel - Re: [PATCH v9 6/7] powerpc/mce: Handle UE event for memcpy

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Message-Id: <7228295c-c4c3-4aa1-1b1a-60b3844705db@linux.vnet.ibm.com>
Date:   Wed, 14 Aug 2019 13:41:50 +0530
From:   Mahesh Jagannath Salgaonkar <mahesh@...ux.vnet.ibm.com>
To:     Santosh Sivaraj <santosh@...six.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Mahesh Salgaonkar <mahesh@...ux.ibm.com>,
        Reza Arbab <arbab@...ux.ibm.com>,
        Balbir Singh <bsingharora@...il.com>,
        Chandan Rajendra <chandan@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        christophe leroy <christophe.leroy@....fr>
Subject: Re: [PATCH v9 6/7] powerpc/mce: Handle UE event for memcpy_mcsafe

On 8/12/19 2:52 PM, Santosh Sivaraj wrote:
> If we take a UE on one of the instructions with a fixup entry, set nip
> to continue execution at the fixup entry. Stop processing the event
> further or print it.
> 
> Co-developed-by: Reza Arbab <arbab@...ux.ibm.com>
> Signed-off-by: Reza Arbab <arbab@...ux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@...ux.ibm.com>
> Signed-off-by: Santosh Sivaraj <santosh@...six.org>

Looks good to me.

Reviewed-by: Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>

Thanks,
-Mahesh.

> ---
>  arch/powerpc/include/asm/mce.h  |  4 +++-
>  arch/powerpc/kernel/mce.c       | 16 ++++++++++++++++
>  arch/powerpc/kernel/mce_power.c | 15 +++++++++++++--
>  3 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
> index f3a6036b6bc0..e1931c8c2743 100644
> --- a/arch/powerpc/include/asm/mce.h
> +++ b/arch/powerpc/include/asm/mce.h
> @@ -122,7 +122,8 @@ struct machine_check_event {
>  			enum MCE_UeErrorType ue_error_type:8;
>  			u8		effective_address_provided;
>  			u8		physical_address_provided;
> -			u8		reserved_1[5];
> +			u8		ignore_event;
> +			u8		reserved_1[4];
>  			u64		effective_address;
>  			u64		physical_address;
>  			u8		reserved_2[8];
> @@ -193,6 +194,7 @@ struct mce_error_info {
>  	enum MCE_Initiator	initiator:8;
>  	enum MCE_ErrorClass	error_class:8;
>  	bool			sync_error;
> +	bool			ignore_event;
>  };
>  
>  #define MAX_MC_EVT	100
> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
> index a3b122a685a5..ec4b3e1087be 100644
> --- a/arch/powerpc/kernel/mce.c
> +++ b/arch/powerpc/kernel/mce.c
> @@ -149,6 +149,7 @@ void save_mce_event(struct pt_regs *regs, long handled,
>  		if (phys_addr != ULONG_MAX) {
>  			mce->u.ue_error.physical_address_provided = true;
>  			mce->u.ue_error.physical_address = phys_addr;
> +			mce->u.ue_error.ignore_event = mce_err->ignore_event;
>  			machine_check_ue_event(mce);
>  		}
>  	}
> @@ -266,8 +267,17 @@ static void machine_process_ue_event(struct work_struct *work)
>  		/*
>  		 * This should probably queued elsewhere, but
>  		 * oh! well
> +		 *
> +		 * Don't report this machine check because the caller has a
> +		 * asked us to ignore the event, it has a fixup handler which
> +		 * will do the appropriate error handling and reporting.
>  		 */
>  		if (evt->error_type == MCE_ERROR_TYPE_UE) {
> +			if (evt->u.ue_error.ignore_event) {
> +				__this_cpu_dec(mce_ue_count);
> +				continue;
> +			}
> +
>  			if (evt->u.ue_error.physical_address_provided) {
>  				unsigned long pfn;
>  
> @@ -301,6 +311,12 @@ static void machine_check_process_queued_event(struct irq_work *work)
>  	while (__this_cpu_read(mce_queue_count) > 0) {
>  		index = __this_cpu_read(mce_queue_count) - 1;
>  		evt = this_cpu_ptr(&mce_event_queue[index]);
> +
> +		if (evt->error_type == MCE_ERROR_TYPE_UE &&
> +		    evt->u.ue_error.ignore_event) {
> +			__this_cpu_dec(mce_queue_count);
> +			continue;
> +		}
>  		machine_check_print_event_info(evt, false, false);
>  		__this_cpu_dec(mce_queue_count);
>  	}
> diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
> index e74816f045f8..1dd87f6f5186 100644
> --- a/arch/powerpc/kernel/mce_power.c
> +++ b/arch/powerpc/kernel/mce_power.c
> @@ -11,6 +11,7 @@
>  
>  #include <linux/types.h>
>  #include <linux/ptrace.h>
> +#include <linux/extable.h>
>  #include <asm/mmu.h>
>  #include <asm/mce.h>
>  #include <asm/machdep.h>
> @@ -18,6 +19,7 @@
>  #include <asm/pte-walk.h>
>  #include <asm/sstep.h>
>  #include <asm/exception-64s.h>
> +#include <asm/extable.h>
>  
>  /*
>   * Convert an address related to an mm to a physical address.
> @@ -559,9 +561,18 @@ static int mce_handle_derror(struct pt_regs *regs,
>  	return 0;
>  }
>  
> -static long mce_handle_ue_error(struct pt_regs *regs)
> +static long mce_handle_ue_error(struct pt_regs *regs,
> +				struct mce_error_info *mce_err)
>  {
>  	long handled = 0;
> +	const struct exception_table_entry *entry;
> +
> +	entry = search_kernel_exception_table(regs->nip);
> +	if (entry) {
> +		mce_err->ignore_event = true;
> +		regs->nip = extable_fixup(entry);
> +		return 1;
> +	}
>  
>  	/*
>  	 * On specific SCOM read via MMIO we may get a machine check
> @@ -594,7 +605,7 @@ static long mce_handle_error(struct pt_regs *regs,
>  				&phys_addr);
>  
>  	if (!handled && mce_err.error_type == MCE_ERROR_TYPE_UE)
> -		handled = mce_handle_ue_error(regs);
> +		handled = mce_handle_ue_error(regs, &mce_err);
>  
>  	save_mce_event(regs, handled, &mce_err, regs->nip, addr, phys_addr);
>  
>