[PATCH 1/2] powerpc/powernv: Add OPAL message log interface
Michael Neuling
mikey at neuling.org
Mon Mar 31 15:21:38 EST 2014
Michael Neuling <mikey at neuling.org> wrote:
> Joel Stanley <joel at jms.id.au> wrote:
>
> > OPAL provides an in-memory circular buffer containing a message log
> > populated with various runtime messages produced by the firmware.
> >
> > Provide a sysfs interface /sys/firmware/opal/messages for userspace to
> > view the messages.
> >
> > Signed-off-by: Joel Stanley <joel at jms.id.au>
> > ---
> > arch/powerpc/include/asm/opal.h | 4 ++
> > arch/powerpc/platforms/powernv/Makefile | 1 +
> > arch/powerpc/platforms/powernv/opal-messages.c | 97 ++++++++++++++++++++++++++
> > arch/powerpc/platforms/powernv/opal.c | 4 +-
> > 4 files changed, 105 insertions(+), 1 deletion(-)
> > create mode 100644 arch/powerpc/platforms/powernv/opal-messages.c
> >
> > diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> > index ffafab0..6aa757e 100644
> > --- a/arch/powerpc/include/asm/opal.h
> > +++ b/arch/powerpc/include/asm/opal.h
> > @@ -729,6 +729,9 @@ typedef struct oppanel_line {
> > /* /sys/firmware/opal */
> > extern struct kobject *opal_kobj;
> >
> > +/* /ibm,opal */
> > +extern struct device_node *opal_node;
> > +
> > /* API functions */
> > int64_t opal_console_write(int64_t term_number, __be64 *length,
> > const uint8_t *buffer);
> > @@ -918,6 +921,7 @@ extern void opal_flash_init(void);
> > extern int opal_elog_init(void);
> > extern void opal_platform_dump_init(void);
> > extern void opal_sys_param_init(void);
> > +extern void opal_messages_init(void);
> >
> > extern int opal_machine_check(struct pt_regs *regs);
> > extern bool opal_mce_check_early_recovery(struct pt_regs *regs);
> > diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
> > index f324ea0..e2ba418 100644
> > --- a/arch/powerpc/platforms/powernv/Makefile
> > +++ b/arch/powerpc/platforms/powernv/Makefile
> > @@ -1,6 +1,7 @@
> > obj-y += setup.o opal-takeover.o opal-wrappers.o opal.o opal-async.o
> > obj-y += opal-rtc.o opal-nvram.o opal-lpc.o opal-flash.o
> > obj-y += rng.o opal-elog.o opal-dump.o opal-sysparam.o opal-sensor.o
> > +obj-y += opal-messages.o
> >
> > obj-$(CONFIG_SMP) += smp.o
> > obj-$(CONFIG_PCI) += pci.o pci-p5ioc2.o pci-ioda.o
> > diff --git a/arch/powerpc/platforms/powernv/opal-messages.c b/arch/powerpc/platforms/powernv/opal-messages.c
> > new file mode 100644
> > index 0000000..3a863e8
> > --- /dev/null
> > +++ b/arch/powerpc/platforms/powernv/opal-messages.c
> > @@ -0,0 +1,97 @@
> > +/*
> > + * PowerNV OPAL in-memory console interface
> > + *
> > + * Copyright 2014 IBM Corp.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version
> > + * 2 of the License, or (at your option) any later version.
> > + */
> > +
> > +#include <asm/io.h>
> > +#include <asm/opal.h>
> > +#include <linux/debugfs.h>
> > +#include <linux/of.h>
> > +#include <linux/types.h>
> > +
> > +/* OPAL in-memory console. Defined in OPAL source at core/console.c */
> > +struct memcons {
> > + __be64 magic;
> > +#define MEMCONS_MAGIC 0x6630696567726173L
>
> 0x6630696567726173 == f0iegras ... Ben!!! :-P
>
> > + __be64 obuf_phys;
> > + __be64 ibuf_phys;
> > + __be32 obuf_size;
> > + __be32 ibuf_size;
> > + __be32 out_pos;
> > +#define MEMCONS_OUT_POS_WRAP 0x80000000u
> > +#define MEMCONS_OUT_POS_MASK 0x00ffffffu
> > + __be32 in_prod;
> > + __be32 in_cons;
> > +};
> > +
> > +static ssize_t opal_messages_read(struct file *file, struct kobject *kobj,
> > + struct bin_attribute *bin_attr, char *to, loff_t pos, size_t count)
> > +{
> > + struct memcons *mc = bin_attr->private;
> > + const char *conbuf;
> > + bool wrapped;
> > + size_t num_read;
> > + int out_pos;
> > +
> > + if (!mc)
> > + return -ENODEV;
> > +
> > + conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
> > + wrapped = be32_to_cpu(mc->out_pos) & MEMCONS_OUT_POS_WRAP;
> > + out_pos = be32_to_cpu(mc->out_pos) & MEMCONS_OUT_POS_MASK;
> > +
>
> Are there ordering issues we need to think about here with reading
> these? Can the messages be written on another CPU at the same time as
> these are being read?
>
> What happens if in between reading wrapped and out_pos the buffer wraps?
> You'd end up getting only a few bytes of console? Maybe you need to
> read wrapped before and after out_pos to make should it's not wrapped in
> between.
wrapped = be32_to_cpu(mc->out_pos) & MEMCONS_OUT_POS_WRAP;
out_pos = be32_to_cpu(mc->out_pos) & MEMCONS_OUT_POS_MASK;
OK, I just realised this is reading from the same location. So yeah,
don't do that. Read it once and calculate wrapped and out_pos from that
single read.
>
> > + if (!wrapped) {
>
> Why the negative case first? Just make it:
>
> if (wrapped) {
> wrapped case
> } else {
> not wrapped case
> }
>
> Also, no curlies needed for single statement.
>
>
> > + num_read = memory_read_from_buffer(to, count, &pos, conbuf,
> > + out_pos);
>
> This is probably not necessary, but do we need to sanity check out_pos <
> obuf_size? I guess we don't generally sanity check numbers from OPAL as
> it can screw us in many other ways anyway.
>
> > + } else {
> > + num_read = memory_read_from_buffer(to, count, &pos,
> > + conbuf + out_pos,
> > + be32_to_cpu(mc->obuf_size) - out_pos);
> > +
> > + if (num_read < 0)
> > + goto out;
> > +
> > + num_read += memory_read_from_buffer(to + num_read,
> > + count - num_read, &pos, conbuf,
> > out_pos);
>
> What if this second read returns an error? num_read += -ERRNO? I think
> you need to check this return independently.
>
> Mikey
>
> > + }
> > +out:
> > + return num_read;
> > +}
> > +
> > +static struct bin_attribute messages_attr = {
> > + .attr = {.name = "messages", .mode = 0444},
> > + .read = opal_messages_read
> > +};
> > +
> > +void __init opal_messages_init(void)
> > +{
> > + u64 mcaddr;
> > + struct memcons *mc;
> > +
> > + if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr)) {
> > + pr_warn("OPAL: Property ibm,opal-memcons not found, no message log\n");
> > + return;
> > + }
> > +
> > + mc = phys_to_virt(mcaddr);
> > + if (!mc) {
> > + pr_warn("OPAL: memory console address is invalid\n");
> > + return;
> > + }
> > +
> > + if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
> > + pr_warn("OPAL: memory console version is invalid\n");
> > + return;
> > + }
> > +
> > + messages_attr.private = mc;
> > +
> > + if (sysfs_create_bin_file(opal_kobj, &messages_attr) != 0)
> > + pr_warn("OPAL: sysfs file creation failed\n");
> > +}
> > diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> > index e92f2f6..2bc032a 100644
> > --- a/arch/powerpc/platforms/powernv/opal.c
> > +++ b/arch/powerpc/platforms/powernv/opal.c
> > @@ -46,7 +46,7 @@ struct mcheck_recoverable_range {
> > static struct mcheck_recoverable_range *mc_recoverable_range;
> > static int mc_recoverable_range_len;
> >
> > -static struct device_node *opal_node;
> > +struct device_node *opal_node;
> > static DEFINE_SPINLOCK(opal_write_lock);
> > extern u64 opal_mc_secondary_handler[];
> > static unsigned int *opal_irqs;
> > @@ -574,6 +574,8 @@ static int __init opal_init(void)
> > opal_platform_dump_init();
> > /* Setup system parameters interface */
> > opal_sys_param_init();
> > + /* Setup message log interface. */
> > + opal_messages_init();
> > }
> >
> > return 0;
> > --
> > 1.9.1
> >
> > _______________________________________________
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