[PATCH v2] cxl: Export AFU error buffer via sysfs
Michael Neuling
mikey at neuling.org
Wed May 20 22:12:44 AEST 2015
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;
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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