On Tue, Aug 22, 2023 at 04:33:39PM -0500, Nathan Lynch via B4 Relay wrote:
> From: Nathan Lynch <nath...@linux.ibm.com>
>
> PowerVM LPARs may retrieve Vital Product Data (VPD) for system
> components using the ibm,get-vpd RTAS function.
>
> We can expose this to user space with a /dev/papr-vpd character
> device, where the programming model is:
>
> struct papr_location_code plc = { .str = "", }; /* obtain all VPD */
> int devfd = open("/dev/papr-vpd", O_WRONLY);
> int vpdfd = ioctl(devfd, PAPR_VPD_CREATE_HANDLE, &plc);
> size_t size = lseek(vpdfd, 0, SEEK_END);
> char *buf = malloc(size);
> pread(devfd, buf, size, 0);
>
> When a file descriptor is obtained from ioctl(PAPR_VPD_CREATE_HANDLE),
> the file contains the result of a complete ibm,get-vpd sequence. The
> file contents are immutable from the POV of user space. To get a new
> view of VPD, clients must create a new handle.
>
> This design choice insulates user space from most of the complexities
> that ibm,get-vpd brings:
>
> * ibm,get-vpd must be called more than once to obtain complete
> results.
> * Only one ibm,get-vpd call sequence should be in progress at a time;
> concurrent sequences will disrupt each other. Callers must have a
> protocol for serializing their use of the function.
> * A call sequence in progress may receive a "VPD changed, try again"
> status, requiring the client to start over. (The driver does not yet
> handle this, but it should be easy to add.)
>
> The memory required for the VPD buffers seems acceptable, around 20KB
> for all VPD on one of my systems. And the value of the
> /rtas/ibm,vpd-size DT property (the estimated maximum size of VPD) is
> consistently 300KB across various systems I've checked.
>
> I've implemented support for this new ABI in the rtas_get_vpd()
> function in librtas, which the vpdupdate command currently uses to
> populate its VPD database. I've verified that an unmodified vpdupdate
> binary generates an identical database when using a librtas.so that
> prefers the new ABI.
>
> Likely remaining work:
>
> * Handle RTAS call status -4 (VPD changed) during ibm,get-vpd call
> sequence.
> * Prevent ibm,get-vpd calls via rtas(2) from disrupting ibm,get-vpd
> call sequences in this driver.
> * (Maybe) implement a poll method for delivering notifications of
> potential changes to VPD, e.g. after a partition migration.
>
> Questions, points for discussion:
>
> * Am I allocating the ioctl numbers correctly?
> * The only way to discover the size of a VPD buffer is
> lseek(SEEK_END). fstat() doesn't work for anonymous fds like
> this. Is this OK, or should the buffer length be discoverable some
> other way?
>
> Signed-off-by: Nathan Lynch <nath...@linux.ibm.com>
> ---
> Documentation/userspace-api/ioctl/ioctl-number.rst | 2 +
> arch/powerpc/include/uapi/asm/papr-vpd.h | 29 ++
> arch/powerpc/platforms/pseries/Makefile | 1 +
> arch/powerpc/platforms/pseries/papr-vpd.c | 353
> +++++++++++++++++++++
> 4 files changed, 385 insertions(+)
>
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst
> b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index 4ea5b837399a..a950545bf7cd 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -349,6 +349,8 @@ Code Seq# Include File
> Comments
>
> <mailto:v...@ratio.de>
> 0xB1 00-1F PPPoX
>
> <mailto:mostr...@styx.uwaterloo.ca>
> +0xB2 00 arch/powerpc/include/uapi/asm/papr-vpd.h
> powerpc/pseries VPD API
> +
> <mailto:linuxppc-dev>
> 0xB3 00 linux/mmc/ioctl.h
> 0xB4 00-0F linux/gpio.h
> <mailto:linux-g...@vger.kernel.org>
> 0xB5 00-0F uapi/linux/rpmsg.h
> <mailto:linux-remotep...@vger.kernel.org>
> diff --git a/arch/powerpc/include/uapi/asm/papr-vpd.h
> b/arch/powerpc/include/uapi/asm/papr-vpd.h
> new file mode 100644
> index 000000000000..aa33217ad5de
> --- /dev/null
> +++ b/arch/powerpc/include/uapi/asm/papr-vpd.h
> @@ -0,0 +1,29 @@
> +// SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
> +#ifndef _UAPI_PAPR_VPD_H_
> +#define _UAPI_PAPR_VPD_H_
> +
> +#include <linux/types.h>
> +#include <asm/ioctl.h>
> +
> +struct papr_location_code {
> + /*
> + * PAPR+ 12.3.2.4 Converged Location Code Rules - Length
> + * Restrictions. 79 characters plus nul.
> + */
> + char str[80];
> +};
> +
> +#define PAPR_VPD_IOCTL_BASE 0xb2
> +
> +#define PAPR_VPD_IO(nr) _IO(PAPR_VPD_IOCTL_BASE, nr)
> +#define PAPR_VPD_IOR(nr, type) _IOR(PAPR_VPD_IOCTL_BASE, nr, type)
> +#define PAPR_VPD_IOW(nr, type) _IOW(PAPR_VPD_IOCTL_BASE, nr, type)
> +#define PAPR_VPD_IOWR(nr, type) _IOWR(PAPR_VPD_IOCTL_BASE, nr, type)
> +
> +/*
> + * ioctl for /dev/papr-vpd. Returns a VPD handle fd corresponding to
> + * the location code.
> + */
> +#define PAPR_VPD_CREATE_HANDLE PAPR_VPD_IOW(0, struct papr_location_code)
> +
> +#endif /* _UAPI_PAPR_VPD_H_ */
> diff --git a/arch/powerpc/platforms/pseries/Makefile
> b/arch/powerpc/platforms/pseries/Makefile
> index 53c3b91af2f7..cbcaa102e2b4 100644
> --- a/arch/powerpc/platforms/pseries/Makefile
> +++ b/arch/powerpc/platforms/pseries/Makefile
> @@ -4,6 +4,7 @@ ccflags-$(CONFIG_PPC_PSERIES_DEBUG) += -DDEBUG
>
> obj-y := lpar.o hvCall.o nvram.o reconfig.o \
> of_helpers.o rtas-work-area.o papr-sysparm.o \
> + papr-vpd.o \
> setup.o iommu.o event_sources.o ras.o \
> firmware.o power.o dlpar.o mobility.o rng.o \
> pci.o pci_dlpar.o eeh_pseries.o msi.o \
> diff --git a/arch/powerpc/platforms/pseries/papr-vpd.c
> b/arch/powerpc/platforms/pseries/papr-vpd.c
> new file mode 100644
> index 000000000000..6fc9ee0c48ae
> --- /dev/null
> +++ b/arch/powerpc/platforms/pseries/papr-vpd.c
> @@ -0,0 +1,353 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#define pr_fmt(fmt) "papr-vpd: " fmt
> +
> +#include <linux/anon_inodes.h>
> +#include <linux/build_bug.h>
> +#include <linux/file.h>
> +#include <linux/fs.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/kernel.h>
> +#include <linux/miscdevice.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
Should be linux/strin_helpers to get string_is_terminated explicitly and not
randomly throuugh another header.
Thanks
Michal
> +#include <asm/machdep.h>
> +#include <asm/papr-vpd.h>
> +#include <asm/rtas-work-area.h>
> +#include <asm/rtas.h>
> +
> +/*
> + * Internal VPD "blob" APIs: for accumulating successive ibm,get-vpd results
> + * into a buffer to be attached to a file descriptor.
> + */
> +struct vpd_blob {
> + const char *data;
> + size_t len;
> +};
> +
> +static struct vpd_blob *vpd_blob_new(void)
> +{
> + return kzalloc(sizeof(struct vpd_blob), GFP_KERNEL_ACCOUNT);
> +}
> +
> +static void vpd_blob_free(struct vpd_blob *blob)
> +{
> + if (blob) {
> + kvfree(blob->data);
> + kfree(blob);
> + }
> +}
> +
> +static int vpd_blob_accumulate(struct vpd_blob *blob, const char *data,
> size_t len)
> +{
> + const size_t new_len = blob->len + len;
> + const size_t old_len = blob->len;
> + const char *old_ptr = blob->data;
> + char *new_ptr;
> +
> + new_ptr = old_ptr ?
> + kvrealloc(old_ptr, old_len, new_len, GFP_KERNEL_ACCOUNT) :
> + kvmalloc(len, GFP_KERNEL_ACCOUNT);
> +
> + if (!new_ptr)
> + return -ENOMEM;
> +
> + memcpy(&new_ptr[old_len], data, len);
> + blob->data = new_ptr;
> + blob->len = new_len;
> + return 0;
> +}
> +
> +/**
> + * struct rtas_ibm_get_vpd_params - Parameters (in and out) for ibm,get-vpd.
> + *
> + * @loc_code: In: Location code buffer. Must be RTAS-addressable.
> + * @work_area: In: Work area buffer for results.
> + * @sequence: In: Sequence number. Out: Next sequence number.
> + * @written: Out: Bytes written by ibm,get-vpd to @work_area.
> + * @status: Out: RTAS call status.
> + */
> +struct rtas_ibm_get_vpd_params {
> + const struct papr_location_code *loc_code;
> + struct rtas_work_area *work_area;
> + u32 sequence;
> + u32 written;
> + s32 status;
> +};
> +
> +static int rtas_ibm_get_vpd(struct rtas_ibm_get_vpd_params *params)
> +{
> + const struct papr_location_code *loc_code = params->loc_code;
> + struct rtas_work_area *work_area = params->work_area;
> + u32 rets[2];
> + s32 fwrc;
> + int ret;
> +
> + do {
> + fwrc = rtas_call(rtas_function_token(RTAS_FN_IBM_GET_VPD), 4, 3,
> + rets,
> + __pa(loc_code),
> + rtas_work_area_phys(work_area),
> + rtas_work_area_size(work_area),
> + params->sequence);
> + } while (rtas_busy_delay(fwrc));
> +
> + switch (fwrc) {
> + case -1:
> + ret = -EIO;
> + break;
> + case -3:
> + ret = -EINVAL;
> + break;
> + case -4:
> + ret = -EAGAIN;
> + break;
> + case 1:
> + params->sequence = rets[0];
> + fallthrough;
> + case 0:
> + params->written = rets[1];
> + /*
> + * Kernel or firmware bug, do not continue.
> + */
> + if (WARN(params->written > rtas_work_area_size(work_area),
> + "possible write beyond end of work area"))
> + ret = -EFAULT;
> + else
> + ret = 0;
> + break;
> + default:
> + ret = -EIO;
> + pr_err_ratelimited("unexpected ibm,get-vpd status %d\n", fwrc);
> + break;
> + }
> +
> + params->status = fwrc;
> + return ret;
> +}
> +
> +struct vpd_sequence_state {
> + struct mutex *mutex; /* always &vpd_sequence_mutex */
> + struct pin_cookie cookie;
> + int error;
> + struct rtas_ibm_get_vpd_params params;
> +};
> +
> +static void vpd_sequence_begin(struct vpd_sequence_state *state,
> + const struct papr_location_code *loc_code)
> +{
> + static DEFINE_MUTEX(vpd_sequence_mutex);
> + /*
> + * Use a static data structure for the location code passed to
> + * RTAS to ensure it's in the RMA and avoid a separate work
> + * area allocation.
> + */
> + static struct papr_location_code static_loc_code;
> +
> + mutex_lock(&vpd_sequence_mutex);
> +
> + static_loc_code = *loc_code;
> + *state = (struct vpd_sequence_state) {
> + .mutex = &vpd_sequence_mutex,
> + .cookie = lockdep_pin_lock(&vpd_sequence_mutex),
> + .params = {
> + .work_area = rtas_work_area_alloc(SZ_4K),
> + .loc_code = &static_loc_code,
> + .sequence = 1,
> + },
> + };
> +}
> +
> +static bool vpd_sequence_done(const struct vpd_sequence_state *state)
> +{
> + bool done;
> +
> + if (state->error)
> + return true;
> +
> + switch (state->params.status) {
> + case 0:
> + if (state->params.written == 0)
> + done = false; /* Initial state. */
> + else
> + done = true; /* All data consumed. */
> + break;
> + case 1:
> + done = false; /* More data available. */
> + break;
> + default:
> + done = true; /* Error encountered. */
> + break;
> + }
> +
> + return done;
> +}
> +
> +static bool vpd_sequence_advance(struct vpd_sequence_state *state)
> +{
> + if (vpd_sequence_done(state))
> + return false;
> +
> + state->error = rtas_ibm_get_vpd(&state->params);
> +
> + return state->error == 0;
> +}
> +
> +static size_t vpd_sequence_get_buffer(const struct vpd_sequence_state
> *state, const char **buf)
> +{
> + *buf = rtas_work_area_raw_buf(state->params.work_area);
> + return state->params.written;
> +}
> +
> +static void vpd_sequence_set_err(struct vpd_sequence_state *state, int err)
> +{
> + state->error = err;
> +}
> +
> +static void vpd_sequence_end(struct vpd_sequence_state *state)
> +{
> + rtas_work_area_free(state->params.work_area);
> + lockdep_unpin_lock(state->mutex, state->cookie);
> + mutex_unlock(state->mutex);
> +}
> +
> +static struct vpd_blob *papr_vpd_retrieve(const struct papr_location_code
> *loc_code)
> +{
> + struct vpd_sequence_state state;
> + struct vpd_blob *blob;
> +
> + blob = vpd_blob_new();
> + if (!blob)
> + return ERR_PTR(-ENOMEM);
> +
> + vpd_sequence_begin(&state, loc_code);
> +
> + while (vpd_sequence_advance(&state)) {
> + const char *buf;
> + const size_t len = vpd_sequence_get_buffer(&state, &buf);
> +
> + vpd_sequence_set_err(&state, vpd_blob_accumulate(blob, buf,
> len));
> + }
> +
> + vpd_sequence_end(&state);
> +
> + if (!state.error)
> + return blob;
> +
> + vpd_blob_free(blob);
> +
> + return ERR_PTR(state.error);
> +}
> +
> +static ssize_t papr_vpd_handle_read(struct file *file, char __user *buf,
> size_t size, loff_t *off)
> +{
> + struct vpd_blob *blob = file->private_data;
> +
> + /* Blobs should always have a valid data pointer and nonzero size. */
> + if (WARN_ON_ONCE(!blob->data))
> + return -EIO;
> + if (WARN_ON_ONCE(blob->len == 0))
> + return -EIO;
> + return simple_read_from_buffer(buf, size, off, blob->data, blob->len);
> +}
> +
> +static int papr_vpd_handle_release(struct inode *inode, struct file *file)
> +{
> + struct vpd_blob *blob = file->private_data;
> +
> + vpd_blob_free(blob);
> +
> + return 0;
> +}
> +
> +static loff_t papr_vpd_handle_seek(struct file *file, loff_t off, int whence)
> +{
> + struct vpd_blob *blob = file->private_data;
> +
> + return fixed_size_llseek(file, off, whence, blob->len);
> +}
> +
> +
> +static const struct file_operations papr_vpd_handle_ops = {
> + .read = papr_vpd_handle_read,
> + .llseek = papr_vpd_handle_seek,
> + .release = papr_vpd_handle_release,
> +};
> +
> +static long papr_vpd_ioctl_create_handle(struct papr_location_code __user
> *ulc)
> +{
> + struct papr_location_code klc;
> + struct vpd_blob *blob;
> + struct file *file;
> + long err;
> + int fd;
> +
> + if (copy_from_user(&klc, ulc, sizeof(klc)))
> + return -EFAULT;
> +
> + if (!string_is_terminated(klc.str, ARRAY_SIZE(klc.str)))
> + return -EINVAL;
> +
> + blob = papr_vpd_retrieve(&klc);
> + if (IS_ERR(blob))
> + return PTR_ERR(blob);
> +
> + fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
> + if (fd < 0) {
> + err = fd;
> + goto free_blob;
> + }
> +
> + file = anon_inode_getfile("[papr-vpd]", &papr_vpd_handle_ops,
> + blob, O_RDONLY);
> + if (IS_ERR(file)) {
> + err = PTR_ERR(file);
> + goto put_fd;
> + }
> +
> + file->f_mode |= FMODE_LSEEK | FMODE_PREAD;
> + fd_install(fd, file);
> + return fd;
> +put_fd:
> + put_unused_fd(fd);
> +free_blob:
> + vpd_blob_free(blob);
> + return err;
> +}
> +
> +/* handler for /dev/papr-vpd */
> +static long papr_vpd_dev_ioctl(struct file *filp, unsigned int ioctl,
> unsigned long arg)
> +{
> + void __user *argp = (__force void __user *)arg;
> + long ret;
> +
> + switch (ioctl) {
> + case PAPR_VPD_CREATE_HANDLE:
> + ret = papr_vpd_ioctl_create_handle(argp);
> + break;
> + default:
> + ret = -ENOIOCTLCMD;
> + break;
> + }
> + return ret;
> +}
> +
> +static const struct file_operations papr_vpd_ops = {
> + .unlocked_ioctl = papr_vpd_dev_ioctl,
> +};
> +
> +static struct miscdevice papr_vpd_dev = {
> + .minor = MISC_DYNAMIC_MINOR,
> + .name = "papr-vpd",
> + .fops = &papr_vpd_ops,
> +};
> +
> +static __init int papr_vpd_init(void)
> +{
> + if (!rtas_function_implemented(RTAS_FN_IBM_GET_VPD))
> + return -ENODEV;
> +
> + return misc_register(&papr_vpd_dev);
> +}
> +machine_device_initcall(pseries, papr_vpd_init);
>
> --
> 2.41.0
>
