[PATCH v2] cxl: Export AFU error buffer via sysfs
Michael Neuling
mikey at neuling.org
Wed May 20 22:46:39 AEST 2015
On Wed, 2015-05-20 at 22:31 +1000, Michael Neuling wrote:
> On Wed, 2015-05-20 at 22:12 +1000, Michael Neuling wrote:
> > On Wed, 2015-05-20 at 16:26 +0530, Vaibhav Jain wrote:
> > > Export the "AFU Error Buffer" via sysfs attribute (afu_err_buf). AFU
> > > error buffer is used by the AFU to report application specific
> > > errors. The contents of this buffer are AFU specific and are intended to
> > > be interpreted by the application interacting with the afu.
> > >
> > > Testing:
> > > - Build against pseries le/be configs.
> > > - Run testing with a special version of memcpy afu on a 'be'
> > > kernel.
> > >
> > > Change-log:
> > > v1 -> v2
> > > - Simplified cxl_afu_read_err_buffer to handle unaligned reads
> > > by performing a short read.
> > >
> > > Signed-off-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
> > > ---
> > > Documentation/ABI/testing/sysfs-class-cxl | 11 ++++++
> > > drivers/misc/cxl/cxl.h | 7 ++++
> > > drivers/misc/cxl/pci.c | 60 +++++++++++++++++++++++++++++++
> > > drivers/misc/cxl/sysfs.c | 33 +++++++++++++++++
> > > 4 files changed, 111 insertions(+)
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-class-cxl b/Documentation/ABI/testing/sysfs-class-cxl
> > > index d46bba8..45e9ce3 100644
> > > --- a/Documentation/ABI/testing/sysfs-class-cxl
> > > +++ b/Documentation/ABI/testing/sysfs-class-cxl
> > > @@ -6,6 +6,17 @@ Example: The real path of the attribute /sys/class/cxl/afu0.0s/irqs_max is
> > >
> > > Slave contexts (eg. /sys/class/cxl/afu0.0s):
> > >
> > > +What: /sys/class/cxl/<afu>/afu_err_buf
> > > +Date: September 2014
> > > +Contact: linuxppc-dev at lists.ozlabs.org
> > > +Description: read only
> > > + AFU Error Buffer contents. The contents of this file are
> > > + application specific and depends on the AFU being used.
> > > + Applications interacting with the AFU can use this attribute
> > > + to know about the current error condition and take appropriate
> > > + action like logging the event etc.
> > > +
> > > +
> > > What: /sys/class/cxl/<afu>/irqs_max
> > > Date: September 2014
> > > Contact: linuxppc-dev at lists.ozlabs.org
> > > diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
> > > index a1cee47..789f077 100644
> > > --- a/drivers/misc/cxl/cxl.h
> > > +++ b/drivers/misc/cxl/cxl.h
> > > @@ -362,6 +362,10 @@ struct cxl_afu {
> > > struct mutex spa_mutex;
> > > spinlock_t afu_cntl_lock;
> > >
> > > + /* AFU error buffer fields and bin attribute for sysfs */
> > > + u64 eb_len, eb_offset;
> > > + struct bin_attribute attr_eb;
> > > +
> > > /*
> > > * Only the first part of the SPA is used for the process element
> > > * linked list. The only other part that software needs to worry about
> > > @@ -563,6 +567,9 @@ static inline void __iomem *_cxl_p2n_addr(struct cxl_afu *afu, cxl_p2n_reg_t reg
> > > u16 cxl_afu_cr_read16(struct cxl_afu *afu, int cr, u64 off);
> > > u8 cxl_afu_cr_read8(struct cxl_afu *afu, int cr, u64 off);
> > >
> > > +ssize_t cxl_afu_read_err_buffer(struct cxl_afu *afu, char *buf,
> > > + loff_t off, size_t count);
> > > +
> > >
> > > struct cxl_calls {
> > > void (*cxl_slbia)(struct mm_struct *mm);
> > > diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
> > > index 1ef0164..162a8fc 100644
> > > --- a/drivers/misc/cxl/pci.c
> > > +++ b/drivers/misc/cxl/pci.c
> > > @@ -593,6 +593,22 @@ static int cxl_read_afu_descriptor(struct cxl_afu *afu)
> > > afu->crs_len = AFUD_CR_LEN(val) * 256;
> > > afu->crs_offset = AFUD_READ_CR_OFF(afu);
> > >
> > > +
> > > + /* eb_len is in multiple of 4K */
> > > + afu->eb_len = AFUD_EB_LEN(AFUD_READ_EB(afu)) * 4096;
> > > + afu->eb_offset = AFUD_READ_EB_OFF(afu);
> > > +
> > > + /* eb_off is 4K aligned so lower 12 bits are always zero */
> > > + if (EXTRACT_PPC_BITS(afu->eb_offset, 0, 11) != 0) {
> > > + dev_warn(&afu->dev,
> > > + "Invalid AFU error buffer offset %Lx\n",
> > > + afu->eb_offset);
> > > + dev_info(&afu->dev,
> > > + "Ignoring AFU error buffer in the descriptor\n");
> > > + /* indicate that no afu buffer exists */
> > > + afu->eb_len = 0;
> > > + }
> > > +
> > > return 0;
> > > }
> > >
> > > @@ -672,6 +688,50 @@ static int sanitise_afu_regs(struct cxl_afu *afu)
> > > return 0;
> > > }
> > >
> > > +/*
> > > + * afu_eb_read:
> > > + * Called from sysfs and reads the afu error info buffer. The h/w only supports
> > > + * 4/8 bytes aligned access. So most of the code tries to get around this by
> > > + * reading full 8 bytes aligned chunks, copying it to a temp buffer and dropping
> > > + * unneeded bytes at the beginning & the end of the requested region.
> > > + */
> > > +ssize_t cxl_afu_read_err_buffer(struct cxl_afu *afu, char *buf,
> > > + loff_t off, size_t count)
> > > +{
> > > + u8 tbuff[8];
> > > + const void __iomem *ebuf = afu->afu_desc_mmio + afu->eb_offset;
> > > +
> > > + count = min((size_t)(afu->eb_len - off), count);
> > > +
> > > + if (unlikely(count <= 0)) {
> > > + /* handle case where no ebuf exists or offset out of bound */
> > > + count = 0;
> > > +
> > > + } else if ((count >= 8) && IS_ALIGNED(off, 8)) {
> > > + /* read all the intermediate aligned words */
> > > +
> > > + count = round_down(off + count, 8) - off;
> > > + _memcpy_fromio(buf,
> > > + ebuf + off, count);
> > > +
> > > + } else if (!IS_ALIGNED(off, 8)) {
> > > + /* handle unaligned access at the beginning */
> > > + _memcpy_fromio(tbuff, ebuf + round_down(off, 8), 8);
> > > +
> > > + count = min((size_t)(ALIGN(off, 8) - off), count);
> > > + memcpy(buf, tbuff + (off & 0x7), count);
> > > +
> > > + } else {
> > > + /* offset is aligned but count < 8 */
> > > + _memcpy_fromio(tbuff, ebuf + round_down(off + count, 8), 8);
> > > +
> > > + count = (off + count) - round_down(off + count, 8);
> > > + memcpy(buf, tbuff, count);
> > > + }
> >
> > I still think this is too complex. How about something like this where
> > we always use a copy buffer (completely untested):
> >
> > copy_size_max = PAGESIZE;
> >
> > ebuf_start = round_down(off, 8);
> > ebuf_length = min(count + 16, copy_size_max); // copy extra for alignment at start and end
> > count = min(count, copy_size_max); // Adjust for max copy
> > length
> > count = count - (off & 7); // Adjust for non aligned offset
> >
> > tbuff = __get_free_page(GFP_KERNEL);
> >
> > _memcpy_fromio(tbuff, ebuf_start, ebuf_length);
> > memcpy(buf, tbuff + (off & 0x7), count); // grab what we need
> >
> > free_page(tbuff);
> >
> > return count;
>
> Slightly updated version as there was a bug in the count calculation.
> Still untested.
>
> copy_size_max = PAGESIZE;
>
> ebuf_start = round_down(off, 8);
> ebuf_length = min(count + 16, copy_size_max); // copy extra for alignment at start and end
We can make these two lines even simpler to read:
ebuf_start = round_down(off, 8);
ebuf_end = round_up(off + count, 8);
ebuf_length = min(ebuf_end - ebuf_start, copy_size_max);
> if ((count + (off & 7)) > copy_size_max)
> /* adjust count if we go past copy_size_max */
> count = copy_size_max - (off & 7);
>
> tbuff = __get_free_page(GFP_KERNEL);
>
> _memcpy_fromio(tbuff, ebuf_start, ebuf_length);
> memcpy(buf, tbuff + (off & 0x7), count); // grab what we need
>
> free_page(tbuff);
>
> return count;
>
> Mikey
>
> >
> > Mikey
> >
> >
> > > +
> > > + return count;
> > > +}
> > > +
> > > static int cxl_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
> > > {
> > > struct cxl_afu *afu;
> > > diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
> > > index d0c38c7..4942d55 100644
> > > --- a/drivers/misc/cxl/sysfs.c
> > > +++ b/drivers/misc/cxl/sysfs.c
> > > @@ -356,6 +356,16 @@ static ssize_t api_version_compatible_show(struct device *device,
> > > return scnprintf(buf, PAGE_SIZE, "%i\n", CXL_API_VERSION_COMPATIBLE);
> > > }
> > >
> > > +static ssize_t afu_eb_read(struct file *filp, struct kobject *kobj,
> > > + struct bin_attribute *bin_attr, char *buf,
> > > + loff_t off, size_t count)
> > > +{
> > > + struct cxl_afu *afu = to_cxl_afu(container_of(kobj,
> > > + struct device, kobj));
> > > +
> > > + return cxl_afu_read_err_buffer(afu, buf, off, count);
> > > +}
> > > +
> > > static struct device_attribute afu_attrs[] = {
> > > __ATTR_RO(mmio_size),
> > > __ATTR_RO(irqs_min),
> > > @@ -534,6 +544,10 @@ void cxl_sysfs_afu_remove(struct cxl_afu *afu)
> > > struct afu_config_record *cr, *tmp;
> > > int i;
> > >
> > > + /* remove the err buffer bin attribute */
> > > + if (afu->eb_len)
> > > + device_remove_bin_file(&afu->dev, &afu->attr_eb);
> > > +
> > > for (i = 0; i < ARRAY_SIZE(afu_attrs); i++)
> > > device_remove_file(&afu->dev, &afu_attrs[i]);
> > >
> > > @@ -555,6 +569,22 @@ int cxl_sysfs_afu_add(struct cxl_afu *afu)
> > > goto err;
> > > }
> > >
> > > + /* conditionally create the add the binary file for error info buffer */
> > > + if (afu->eb_len) {
> > > + afu->attr_eb.attr.name = "afu_err_buff";
> > > + afu->attr_eb.attr.mode = S_IRUGO;
> > > + afu->attr_eb.size = afu->eb_len;
> > > + afu->attr_eb.read = afu_eb_read;
> > > +
> > > + rc = device_create_bin_file(&afu->dev, &afu->attr_eb);
> > > + if (rc) {
> > > + dev_err(&afu->dev,
> > > + "Unable to create eb attr for the afu. Err(%d)\n",
> > > + rc);
> > > + goto err;
> > > + }
> > > + }
> > > +
> > > for (i = 0; i < afu->crs_num; i++) {
> > > cr = cxl_sysfs_afu_new_cr(afu, i);
> > > if (IS_ERR(cr)) {
> > > @@ -570,6 +600,9 @@ err1:
> > > cxl_sysfs_afu_remove(afu);
> > > return rc;
> > > err:
> > > + /* reset the eb_len as we havent created the bin attr */
> > > + afu->eb_len = 0;
> > > +
> > > for (i--; i >= 0; i--)
> > > device_remove_file(&afu->dev, &afu_attrs[i]);
> > > return rc;
> >
>
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