Date:   Wed, 15 Jul 2020 12:22:13 -0700
From:   rishabhb@...eaurora.org
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        bjorn.andersson@...aro.org, tsoni@...eaurora.org,
        psodagud@...eaurora.org, sidgup@...eaurora.org,
        linux-remoteproc-owner@...r.kernel.org
Subject: Re: [PATCH v7 3/4] remoteproc: Add inline coredump functionality

On 2020-07-14 10:53, Mathieu Poirier wrote:
> On Thu, Jul 09, 2020 at 01:31:55PM -0700, Rishabh Bhatnagar wrote:
>> The current coredump implementation uses vmalloc area to copy
>> all the segments. But this might put strain on low memory targets
>> as the firmware size sometimes is in tens of MBs. The situation
>> becomes worse if there are multiple remote processors undergoing
>> recovery at the same time. This patch adds inline coredump
>> functionality that avoids extra memory usage. This requires
>> recovery to be halted until data is read by userspace and free
>> function is called. Also modify the qcom_q6v5_mss driver to include
>> size and offset in the segment dump function.
>> 
>> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
>> Reviewed-by: Sibi Sankar <sibis@...eaurora.org>
>> ---
>>  drivers/remoteproc/qcom_q6v5_mss.c       |  11 ++-
>>  drivers/remoteproc/remoteproc_coredump.c | 160 
>> +++++++++++++++++++++++++++----
>>  include/linux/remoteproc.h               |  21 +++-
>>  3 files changed, 166 insertions(+), 26 deletions(-)
>> 
>> diff --git a/drivers/remoteproc/qcom_q6v5_mss.c 
>> b/drivers/remoteproc/qcom_q6v5_mss.c
>> index c6ce032..79df354 100644
>> --- a/drivers/remoteproc/qcom_q6v5_mss.c
>> +++ b/drivers/remoteproc/qcom_q6v5_mss.c
>> @@ -1199,11 +1199,12 @@ static int q6v5_mpss_load(struct q6v5 *qproc)
>> 
>>  static void qcom_q6v5_dump_segment(struct rproc *rproc,
>>  				   struct rproc_dump_segment *segment,
>> -				   void *dest)
>> +				   void *dest, size_t cp_offset, size_t size)
> 
> Now that I'm taking another look at this, refactoring 
> qcom_q6v5_dump_segment()
> should be in another patch - please split them.
> 
Hi Mathieu,
Thanks for reviewing.

Since I'm changing the API signature if we just take this patch without 
q6v5_mss
changes (in a separate patch) it would cause compilation errors. Is that 
ok?
>>  {
>>  	int ret = 0;
>>  	struct q6v5 *qproc = rproc->priv;
>>  	int offset = segment->da - qproc->mpss_reloc;
>> +	size_t cp_size = size ? size : segment->size;
> 
> I can't find a scenario where size is 0 - can you explain when
> such condition occurs?
> 
There is no such case right now. I can get rid of the check.
> Thanks,
> Mathieu
> 
> 
>>  	void *ptr = NULL;
>> 
>>  	/* Unlock mba before copying segments */
>> @@ -1219,16 +1220,16 @@ static void qcom_q6v5_dump_segment(struct 
>> rproc *rproc,
>>  	}
>> 
>>  	if (!ret)
>> -		ptr = ioremap_wc(qproc->mpss_phys + offset, segment->size);
>> +		ptr = ioremap_wc(qproc->mpss_phys + offset + cp_offset, cp_size);
>> 
>>  	if (ptr) {
>> -		memcpy(dest, ptr, segment->size);
>> +		memcpy(dest, ptr, cp_size);
>>  		iounmap(ptr);
>>  	} else {
>> -		memset(dest, 0xff, segment->size);
>> +		memset(dest, 0xff, cp_size);
>>  	}
>> 
>> -	qproc->current_dump_size += segment->size;
>> +	qproc->current_dump_size += cp_size;
>> 
>>  	/* Reclaim mba after copying segments */
>>  	if (qproc->current_dump_size == qproc->total_dump_size) {
>> diff --git a/drivers/remoteproc/remoteproc_coredump.c 
>> b/drivers/remoteproc/remoteproc_coredump.c
>> index ded0244..646886f 100644
>> --- a/drivers/remoteproc/remoteproc_coredump.c
>> +++ b/drivers/remoteproc/remoteproc_coredump.c
>> @@ -5,6 +5,7 @@
>>   * Copyright (c) 2020, The Linux Foundation. All rights reserved.
>>   */
>> 
>> +#include <linux/completion.h>
>>  #include <linux/devcoredump.h>
>>  #include <linux/device.h>
>>  #include <linux/kernel.h>
>> @@ -12,6 +13,12 @@
>>  #include "remoteproc_internal.h"
>>  #include "remoteproc_elf_helpers.h"
>> 
>> +struct rproc_coredump_state {
>> +	struct rproc *rproc;
>> +	void *header;
>> +	struct completion dump_done;
>> +};
>> +
>>  /**
>>   * rproc_coredump_cleanup() - clean up dump_segments list
>>   * @rproc: the remote processor handle
>> @@ -72,7 +79,8 @@ int rproc_coredump_add_custom_segment(struct rproc 
>> *rproc,
>>  				      dma_addr_t da, size_t size,
>>  				      void (*dumpfn)(struct rproc *rproc,
>>  						     struct rproc_dump_segment *segment,
>> -						     void *dest),
>> +						     void *dest, size_t offset,
>> +						     size_t size),
>>  				      void *priv)
>>  {
>>  	struct rproc_dump_segment *segment;
>> @@ -114,12 +122,110 @@ int rproc_coredump_set_elf_info(struct rproc 
>> *rproc, u8 class, u16 machine)
>>  }
>>  EXPORT_SYMBOL(rproc_coredump_set_elf_info);
>> 
>> +static void rproc_coredump_free(void *data)
>> +{
>> +	struct rproc_coredump_state *dump_state = data;
>> +
>> +	complete(&dump_state->dump_done);
>> +	vfree(dump_state->header);
>> +}
>> +
>> +static void *rproc_coredump_find_segment(loff_t user_offset,
>> +					 struct list_head *segments,
>> +					 size_t *data_left)
>> +{
>> +	struct rproc_dump_segment *segment;
>> +
>> +	list_for_each_entry(segment, segments, node) {
>> +		if (user_offset < segment->size) {
>> +			*data_left = segment->size - user_offset;
>> +			return segment;
>> +		}
>> +		user_offset -= segment->size;
>> +	}
>> +
>> +	*data_left = 0;
>> +	return NULL;
>> +}
>> +
>> +static void rproc_copy_segment(struct rproc *rproc, void *dest,
>> +			       struct rproc_dump_segment *segment,
>> +			       size_t offset, size_t size)
>> +{
>> +	void *ptr;
>> +
>> +	if (segment->dump) {
>> +		segment->dump(rproc, segment, dest, offset, size);
>> +	} else {
>> +		ptr = rproc_da_to_va(rproc, segment->da + offset, size);
>> +		if (!ptr) {
>> +			dev_err(&rproc->dev,
>> +				"invalid copy request for segment %pad with offset %zu and size 
>> %zu)\n",
>> +				&segment->da, offset, size);
>> +			memset(dest, 0xff, size);
>> +		} else {
>> +			memcpy(dest, ptr, size);
>> +		}
>> +	}
>> +}
>> +
>> +static ssize_t rproc_coredump_read(char *buffer, loff_t offset, 
>> size_t count,
>> +				   void *data, size_t header_sz)
>> +{
>> +	size_t seg_data, bytes_left = count;
>> +	ssize_t copy_sz;
>> +	struct rproc_dump_segment *seg;
>> +	struct rproc_coredump_state *dump_state = data;
>> +	struct rproc *rproc = dump_state->rproc;
>> +	void *elfcore = dump_state->header;
>> +
>> +	/* Copy the vmalloc'ed header first. */
>> +	if (offset < header_sz) {
>> +		copy_sz = memory_read_from_buffer(buffer, count, &offset,
>> +						  elfcore, header_sz);
>> +
>> +		return copy_sz;
>> +	}
>> +
>> +	/*
>> +	 * Find out the segment memory chunk to be copied based on offset.
>> +	 * Keep copying data until count bytes are read.
>> +	 */
>> +	while (bytes_left) {
>> +		seg = rproc_coredump_find_segment(offset - header_sz,
>> +						  &rproc->dump_segments,
>> +						  &seg_data);
>> +		/* EOF check */
>> +		if (!seg) {
>> +			dev_info(&rproc->dev, "Ramdump done, %lld bytes read",
>> +				 offset);
>> +			break;
>> +		}
>> +
>> +		copy_sz = min_t(size_t, bytes_left, seg_data);
>> +
>> +		rproc_copy_segment(rproc, buffer, seg, seg->size - seg_data,
>> +				   copy_sz);
>> +
>> +		offset += copy_sz;
>> +		buffer += copy_sz;
>> +		bytes_left -= copy_sz;
>> +	}
>> +
>> +	return count - bytes_left;
>> +}
>> +
>>  /**
>>   * rproc_coredump() - perform coredump
>>   * @rproc:	rproc handle
>>   *
>>   * This function will generate an ELF header for the registered 
>> segments
>> - * and create a devcoredump device associated with rproc.
>> + * and create a devcoredump device associated with rproc. Based on 
>> the
>> + * coredump configuration this function will directly copy the 
>> segments
>> + * from device memory to userspace or copy segments from device 
>> memory to
>> + * a separate buffer, which can then be read by userspace.
>> + * The first approach avoids using extra vmalloc memory. But it will 
>> stall
>> + * recovery flow until dump is read by userspace.
>>   */
>>  void rproc_coredump(struct rproc *rproc)
>>  {
>> @@ -129,11 +235,13 @@ void rproc_coredump(struct rproc *rproc)
>>  	size_t data_size;
>>  	size_t offset;
>>  	void *data;
>> -	void *ptr;
>>  	u8 class = rproc->elf_class;
>>  	int phnum = 0;
>> +	struct rproc_coredump_state dump_state;
>> +	enum rproc_dump_mechanism dump_conf = rproc->dump_conf;
>> 
>> -	if (list_empty(&rproc->dump_segments))
>> +	if (list_empty(&rproc->dump_segments) ||
>> +	    dump_conf == RPROC_COREDUMP_DISABLED)
>>  		return;
>> 
>>  	if (class == ELFCLASSNONE) {
>> @@ -143,7 +251,14 @@ void rproc_coredump(struct rproc *rproc)
>> 
>>  	data_size = elf_size_of_hdr(class);
>>  	list_for_each_entry(segment, &rproc->dump_segments, node) {
>> -		data_size += elf_size_of_phdr(class) + segment->size;
>> +		/*
>> +		 * For default configuration buffer includes headers & segments.
>> +		 * For inline dump buffer just includes headers as segments are
>> +		 * directly read from device memory.
>> +		 */
>> +		data_size += elf_size_of_phdr(class);
>> +		if (dump_conf == RPROC_COREDUMP_DEFAULT)
>> +			data_size += segment->size;
>> 
>>  		phnum++;
>>  	}
>> @@ -182,23 +297,30 @@ void rproc_coredump(struct rproc *rproc)
>>  		elf_phdr_set_p_flags(class, phdr, PF_R | PF_W | PF_X);
>>  		elf_phdr_set_p_align(class, phdr, 0);
>> 
>> -		if (segment->dump) {
>> -			segment->dump(rproc, segment, data + offset);
>> -		} else {
>> -			ptr = rproc_da_to_va(rproc, segment->da, segment->size);
>> -			if (!ptr) {
>> -				dev_err(&rproc->dev,
>> -					"invalid coredump segment (%pad, %zu)\n",
>> -					&segment->da, segment->size);
>> -				memset(data + offset, 0xff, segment->size);
>> -			} else {
>> -				memcpy(data + offset, ptr, segment->size);
>> -			}
>> -		}
>> +		if (dump_conf == RPROC_COREDUMP_DEFAULT)
>> +			rproc_copy_segment(rproc, data + offset, segment, 0,
>> +					   segment->size);
>> 
>>  		offset += elf_phdr_get_p_filesz(class, phdr);
>>  		phdr += elf_size_of_phdr(class);
>>  	}
>> 
>> -	dev_coredumpv(&rproc->dev, data, data_size, GFP_KERNEL);
>> +	if (dump_conf == RPROC_COREDUMP_DEFAULT) {
>> +		dev_coredumpv(&rproc->dev, data, data_size, GFP_KERNEL);
>> +		return;
>> +	}
>> +
>> +	/* Initialize the dump state struct to be used by 
>> rproc_coredump_read */
>> +	dump_state.rproc = rproc;
>> +	dump_state.header = data;
>> +	init_completion(&dump_state.dump_done);
>> +
>> +	dev_coredumpm(&rproc->dev, NULL, &dump_state, data_size, GFP_KERNEL,
>> +		      rproc_coredump_read, rproc_coredump_free);
>> +
>> +	/*
>> +	 * Wait until the dump is read and free is called. Data is freed
>> +	 * by devcoredump framework automatically after 5 minutes.
>> +	 */
>> +	wait_for_completion(&dump_state.dump_done);
>>  }
>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>> index e7b7bab..38d037d 100644
>> --- a/include/linux/remoteproc.h
>> +++ b/include/linux/remoteproc.h
>> @@ -435,6 +435,20 @@ enum rproc_crash_type {
>>  };
>> 
>>  /**
>> + * enum rproc_dump_mechanism - Coredump options for core
>> + * @RPROC_COREDUMP_DEFAULT:	Copy dump to separate buffer and carry on 
>> with
>> +				recovery
>> + * @RPROC_COREDUMP_INLINE:	Read segments directly from device memory. 
>> Stall
>> +				recovery until all segments are read
>> + * @RPROC_COREDUMP_DISABLED:	Don't perform any dump
>> + */
>> +enum rproc_dump_mechanism {
>> +	RPROC_COREDUMP_DEFAULT,
>> +	RPROC_COREDUMP_INLINE,
>> +	RPROC_COREDUMP_DISABLED,
>> +};
>> +
>> +/**
>>   * struct rproc_dump_segment - segment info from ELF header
>>   * @node:	list node related to the rproc segment list
>>   * @da:		device address of the segment
>> @@ -451,7 +465,7 @@ struct rproc_dump_segment {
>> 
>>  	void *priv;
>>  	void (*dump)(struct rproc *rproc, struct rproc_dump_segment 
>> *segment,
>> -		     void *dest);
>> +		     void *dest, size_t offset, size_t size);
>>  	loff_t offset;
>>  };
>> 
>> @@ -466,6 +480,7 @@ struct rproc_dump_segment {
>>   * @dev: virtual device for refcounting and common remoteproc 
>> behavior
>>   * @power: refcount of users who need this rproc powered up
>>   * @state: state of the device
>> + * @dump_conf: Currently selected coredump configuration
>>   * @lock: lock which protects concurrent manipulations of the rproc
>>   * @dbg_dir: debugfs directory of this rproc device
>>   * @traces: list of trace buffers
>> @@ -499,6 +514,7 @@ struct rproc {
>>  	struct device dev;
>>  	atomic_t power;
>>  	unsigned int state;
>> +	enum rproc_dump_mechanism dump_conf;
>>  	struct mutex lock;
>>  	struct dentry *dbg_dir;
>>  	struct list_head traces;
>> @@ -630,7 +646,8 @@ int rproc_coredump_add_custom_segment(struct rproc 
>> *rproc,
>>  				      dma_addr_t da, size_t size,
>>  				      void (*dumpfn)(struct rproc *rproc,
>>  						     struct rproc_dump_segment *segment,
>> -						     void *dest),
>> +						     void *dest, size_t offset,
>> +						     size_t size),
>>  				      void *priv);
>>  int rproc_coredump_set_elf_info(struct rproc *rproc, u8 class, u16 
>> machine);
>> 
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>> 

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