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Date:   Tue, 7 Jul 2020 15:55:00 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>
Cc:     linux-remoteproc <linux-remoteproc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        tsoni <tsoni@...eaurora.org>, psodagud <psodagud@...eaurora.org>,
        Siddharth Gupta <sidgup@...eaurora.org>,
        linux-remoteproc-owner@...r.kernel.org
Subject: Re: [PATCH v6 2/3] remoteproc: Add inline coredump functionality

On Tue, 7 Jul 2020 at 11:12, <rishabhb@...eaurora.org> wrote:
>
> On 2020-07-06 10:47, Mathieu Poirier wrote:
> > On Mon, Jun 29, 2020 at 01:02:12PM -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.
> >>
> >> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
> >> ---
> >>  drivers/remoteproc/qcom_q6v5_mss.c       |   9 +-
> >>  drivers/remoteproc/remoteproc_coredump.c | 160
> >> +++++++++++++++++++++++++++----
> >>  include/linux/remoteproc.h               |  21 +++-
> >>  3 files changed, 165 insertions(+), 25 deletions(-)
> >>
> >> diff --git a/drivers/remoteproc/qcom_q6v5_mss.c
> >> b/drivers/remoteproc/qcom_q6v5_mss.c
> >> index 903b2bb..d4ff9b8 100644
> >> --- a/drivers/remoteproc/qcom_q6v5_mss.c
> >> +++ b/drivers/remoteproc/qcom_q6v5_mss.c
> >> @@ -1200,12 +1200,13 @@ 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)
> >>  {
> >>      int ret = 0;
> >>      struct q6v5 *qproc = rproc->priv;
> >>      unsigned long mask = BIT((unsigned long)segment->priv);
> >>      int offset = segment->da - qproc->mpss_reloc;
> >> +    size_t cp_size = size ? size : segment->size;
> >>      void *ptr = NULL;
> >
> > On the V4 of this set the above line was:
> >
> > +       void *ptr = rproc_da_to_va(rproc, segment->da + offset,
> > copy_size);
> >
> > Back then both Bjorn and I had RB'ed this set and all that was required
> > was a
> > rebase to linux-next.  On V5 and V6 our RBs have been removed, the
> > above has
> > been changed and an iounmap() was been added below.  Yet nothing in the
> > cover
> > letter provides an explanation that justifies the modification.
> >
> > What is going on here?
> >
> Hi Mathieu,
> The qcom_q6v5_dump_segment code has changed in the latest tip. That's
> why I had to
> make modifications to my patch. Sibi reviewed this patch as he made the
> above
> changes to mss driver and he has reviewed and tested from his side. He
> has
> also created a minor fix in the driver to make inline dumps work for
> mss.
> https://patchwork.kernel.org/patch/11637159/
>
> I removed the reviewed-by because I made some modifications to this
> patch
> and was not sure if the reviewed-by still applied. Let me know if i
> should add it
> again.

Removing the reviewed-by was the right thing to do but not mentioning
that something had changed in the cover letter was perplexing.  I had
to fish out previous revisions and compare each line to figure out
what has happened, an exercise that was time consuming.

I will take another look at your patchset but it may not be until next week.

Thanks,
Mathieu

> >>
> >>      /* Unlock mba before copying segments */
> >> @@ -1221,13 +1222,13 @@ 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->dump_segment_mask |= mask;
> >> 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..43e45a3 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: Currenlty 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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