RE: [PATCH v2 24/27] nvdimm/ocxl: Implement Overwrite

From: Alastair D'Silva
Date: Wed Feb 19 2020 - 00:22:44 EST

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On Mon, 2020-02-03 at 15:10 +0000, Jonathan Cameron wrote:
> On Tue, 3 Dec 2019 14:46:52 +1100
> Alastair D'Silva <alastair@xxxxxxxxxxx> wrote:
>
> > From: Alastair D'Silva <alastair@xxxxxxxxxxx>
> >
> > The near storage command 'Secure Erase' overwrites all data on the
> > media.
> >
> > This patch hooks it up to the security function 'overwrite'.
> >
> > Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
>
> A few things to tidy up in here.
>
> Thanks,
>
> Jonathan
>
>
> > ---
> > drivers/nvdimm/ocxl/scm.c | 164
> > ++++++++++++++++++++++++++++-
> > drivers/nvdimm/ocxl/scm_internal.c | 1 +
> > drivers/nvdimm/ocxl/scm_internal.h | 17 +++
> > 3 files changed, 180 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/nvdimm/ocxl/scm.c b/drivers/nvdimm/ocxl/scm.c
> > index a81eb5916eb3..8deb7862793c 100644
> > --- a/drivers/nvdimm/ocxl/scm.c
> > +++ b/drivers/nvdimm/ocxl/scm.c
> > @@ -169,6 +169,86 @@ static int scm_reserve_metadata(struct
> > scm_data *scm_data,
> > return 0;
> > }
> >
> > +/**
> > + * scm_overwrite() - Overwrite all data on the card
> > + * @scm_data: The SCM device data
>
> I would mention in here that this exists with the lock held and
> where that is unlocked again.

Ok

>
> > + * Return: 0 on success
> > + */
> > +int scm_overwrite(struct scm_data *scm_data)
> > +{
> > + int rc;
> > +
> > + mutex_lock(&scm_data->ns_command.lock);
> > +
> > + rc = scm_ns_command_request(scm_data, NS_COMMAND_SECURE_ERASE);
> > + if (rc)
>
> Perhaps change that goto label to reflect it is the error path rather
> than a shared exit route.
>

Ok

> > + goto out;
> > +
> > + rc = scm_ns_command_execute(scm_data);
> > + if (rc)
> > + goto out;
> > +
> > + scm_data->overwrite_state = SCM_OVERWRITE_BUSY;
> > +
> > + return 0;
> > +
> > +out:
> > + mutex_unlock(&scm_data->ns_command.lock);
> > + return rc;
> > +}
> > +
> > +/**
> > + * scm_secop_overwrite() - Overwrite all data on the card
> > + * @nvdimm: The nvdimm representation of the SCM device to start
> > the overwrite on
> > + * @key_data: Unused (no security key implementation)
> > + * Return: 0 on success
> > + */
> > +static int scm_secop_overwrite(struct nvdimm *nvdimm,
> > + const struct nvdimm_key_data *key_data)
> > +{
> > + struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
> > +
> > + return scm_overwrite(scm_data);
> > +}
> > +
> > +/**
> > + * scm_secop_query_overwrite() - Get the current overwrite state
> > + * @nvdimm: The nvdimm representation of the SCM device to start
> > the overwrite on
> > + * Return: 0 if successful or idle, -EBUSY if busy, -EFAULT if
> > failed
> > + */
> > +static int scm_secop_query_overwrite(struct nvdimm *nvdimm)
> > +{
> > + struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
> > +
> > + if (scm_data->overwrite_state == SCM_OVERWRITE_BUSY)
> > + return -EBUSY;
> > +
> > + if (scm_data->overwrite_state == SCM_OVERWRITE_FAILED)
> > + return -EFAULT;
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * scm_secop_get_flags() - return the security flags for the SCM
> > device
>
> All params need to documented in kernel-doc comments.
Ok

>
> > + */
> > +static unsigned long scm_secop_get_flags(struct nvdimm *nvdimm,
> > + enum nvdimm_passphrase_type ptype)
> > +{
> > + struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
> > +
> > + if (scm_data->overwrite_state == SCM_OVERWRITE_BUSY)
> > + return BIT(NVDIMM_SECURITY_OVERWRITE);
> > +
> > + return BIT(NVDIMM_SECURITY_DISABLED);
> > +}
> > +
> > +static const struct nvdimm_security_ops sec_ops = {
> > + .get_flags = scm_secop_get_flags,
> > + .overwrite = scm_secop_overwrite,
> > + .query_overwrite = scm_secop_query_overwrite,
> > +};
> > +
> > /**
> > * scm_register_lpc_mem() - Discover persistent memory on a device
> > and register it with the NVDIMM subsystem
> > * @scm_data: The SCM device data
> > @@ -224,10 +304,10 @@ static int scm_register_lpc_mem(struct
> > scm_data *scm_data)
> > set_bit(NDD_ALIASING, &nvdimm_flags);
> >
> > snprintf(serial, sizeof(serial), "%llx", fn_config->serial);
> > - nd_mapping_desc.nvdimm = nvdimm_create(scm_data->nvdimm_bus,
> > scm_data,
> > + nd_mapping_desc.nvdimm = __nvdimm_create(scm_data->nvdimm_bus,
> > scm_data,
> > scm_dimm_attribute_groups,
> > nvdimm_flags, nvdimm_cmd_mask,
> > - 0, NULL);
> > + 0, NULL, serial, &sec_ops);
> > if (!nd_mapping_desc.nvdimm)
> > return -ENOMEM;
> >
> > @@ -1530,6 +1610,83 @@ static void scm_dump_error_log(struct
> > scm_data *scm_data)
> > kfree(buf);
> > }
> >
> > +static void scm_handle_nscra_doorbell(struct scm_data *scm_data)
> > +{
> > + int rc;
> > +
> > + if (scm_data->ns_command.op_code == NS_COMMAND_SECURE_ERASE) {
>
> Feels likely that we are going to end up with quite a few blocks like
> this as
> the driver is extended. Perhaps just start out with a switch
> statement and
> separate functions that it calls?
>
At the moment, this is the only near storage command documented on the
device, and I don't think there will be any more.

> > + u64 success, attempted;
> > +
>
> One is enough here.
>
It's not, there is a comparison between them later.

> > +
> > + rc = scm_ns_response(scm_data);
> > + if (rc < 0) {
> > + scm_data->overwrite_state =
> > SCM_OVERWRITE_FAILED;
>
> If this were a separate function as suggested above, I'd use a goto
> to ensure we
> unlock in all paths.
>
> > + mutex_unlock(&scm_data->ns_command.lock);
> > + return;
> > + }
> > + if (rc != STATUS_SUCCESS)
> > + scm_warn_status(scm_data, "Unexpected status
> > from overwrite", rc);
> > +
> > + rc = ocxl_global_mmio_read64(scm_data->ocxl_afu,
> > + scm_data-
> > >ns_command.response_offset +
> > + NS_RESPONSE_SECURE_ERASE_A
> > CCESSIBLE_SUCCESS,
> > + OCXL_HOST_ENDIAN,
> > &success);
> > + if (rc) {
> > + scm_data->overwrite_state =
> > SCM_OVERWRITE_FAILED;
> > + mutex_unlock(&scm_data->ns_command.lock);
> > + return;
> > + }
> > +
> > + rc = ocxl_global_mmio_read64(scm_data->ocxl_afu,
> > + scm_data-
> > >ns_command.response_offset +
> > + NS_RESPONSE_SECURE_ERASE_A
> > CCESSIBLE_ATTEMPTED,
> > + OCXL_HOST_ENDIAN,
> > &attempted);
> > + if (rc) {
> > + scm_data->overwrite_state =
> > SCM_OVERWRITE_FAILED;
> > + mutex_unlock(&scm_data->ns_command.lock);
> > + return;
> > + }
> > +
> > + scm_data->overwrite_state = SCM_OVERWRITE_SUCCESS;
> > + if (success != attempted)
> > + scm_data->overwrite_state =
> > SCM_OVERWRITE_FAILED;
> > +
> > + dev_info(&scm_data->dev,
> > + "Overwritten %llu/%llu accessible pages",
> > success, attempted);
>
> Do we want to spam the log? Feels like dev_dbg maybe?

This only occurs once per overwrite operation. Each overwrite operation
is expected to take a non-trivial amount of time.

>
> > +
> > + rc = ocxl_global_mmio_read64(scm_data->ocxl_afu,
> > + scm_data-
> > >ns_command.response_offset +
> > + NS_RESPONSE_SECURE_ERASE_D
> > EFECTIVE_SUCCESS,
> > + OCXL_HOST_ENDIAN,
> > &success);
> > + if (rc) {
> > + scm_data->overwrite_state =
> > SCM_OVERWRITE_FAILED;
> > + mutex_unlock(&scm_data->ns_command.lock);
> > + return;
> > + }
> > +
> > + rc = ocxl_global_mmio_read64(scm_data->ocxl_afu,
> > + scm_data-
> > >ns_command.response_offset +
> > + NS_RESPONSE_SECURE_ERASE_D
> > EFECTIVE_ATTEMPTED,
> > + OCXL_HOST_ENDIAN,
> > &attempted);
> > + if (rc) {
> > + scm_data->overwrite_state =
> > SCM_OVERWRITE_FAILED;
> > + mutex_unlock(&scm_data->ns_command.lock);
> > + return;
> > + }
> > +
> > + if (success != attempted)
> > + scm_data->overwrite_state =
> > SCM_OVERWRITE_FAILED;
> > +
> > + dev_info(&scm_data->dev,
> > + "Overwritten %llu/%llu defective pages",
> > success, attempted);
>
> Again, maybe dev_dbg?
>
(see above)

> > +
> > + scm_ns_response_handled(scm_data);
> > +
> > + mutex_unlock(&scm_data->ns_command.lock);
> > + return;
> > + }
> > +}
> > +
> > static irqreturn_t scm_imn0_handler(void *private)
> > {
> > struct scm_data *scm_data = private;
> > @@ -1537,6 +1694,9 @@ static irqreturn_t scm_imn0_handler(void
> > *private)
> >
> > (void)scm_chi(scm_data, &chi);
> >
> > + if (chi & GLOBAL_MMIO_CHI_NSCRA)
> > + scm_handle_nscra_doorbell(scm_data);
> > +
> > if (chi & GLOBAL_MMIO_CHI_ELA) {
> > dev_warn(&scm_data->dev, "Error log is available\n");
> >
> > diff --git a/drivers/nvdimm/ocxl/scm_internal.c
> > b/drivers/nvdimm/ocxl/scm_internal.c
> > index 8fc849610eaa..db919a23c69b 100644
> > --- a/drivers/nvdimm/ocxl/scm_internal.c
> > +++ b/drivers/nvdimm/ocxl/scm_internal.c
> > @@ -173,6 +173,7 @@ int scm_ns_response_handled(const struct
> > scm_data *scm_data)
> > OCXL_LITTLE_ENDIAN,
> > GLOBAL_MMIO_CHI_NSCRA);
> > }
> >
> > +
>
> Stray blank line..
Sneaky things...

>
> > void scm_warn_status(const struct scm_data *scm_data, const char
> > *message,
> > u8 status)
> > {
> > diff --git a/drivers/nvdimm/ocxl/scm_internal.h
> > b/drivers/nvdimm/ocxl/scm_internal.h
> > index af19813a7f75..4a29088612a9 100644
> > --- a/drivers/nvdimm/ocxl/scm_internal.h
> > +++ b/drivers/nvdimm/ocxl/scm_internal.h
> > @@ -70,6 +70,15 @@
> > #define ADMIN_COMMAND_CMD_CAPS 0x08u
> > #define ADMIN_COMMAND_MAX 0x08u
> >
> > +#define NS_COMMAND_SECURE_ERASE 0x20ull
> > +
> > +#define NS_RESPONSE_SECURE_ERASE_ACCESSIBLE_SUCCESS 0x20
> > +#define NS_RESPONSE_SECURE_ERASE_ACCESSIBLE_ATTEMPTED 0x28
> > +#define NS_RESPONSE_SECURE_ERASE_DEFECTIVE_SUCCESS 0x30
> > +#define NS_RESPONSE_SECURE_ERASE_DEFECTIVE_ATTEMPTED 0x38
> > +
>
> Lot of blank lines...
Whoops
>
> > +
> > +
> > #define STATUS_SUCCESS 0x00
> > #define STATUS_MEM_UNAVAILABLE 0x20
> > #define STATUS_BAD_OPCODE 0x50
> > @@ -99,6 +108,13 @@ struct scm_function_0 {
> > struct ocxl_fn *ocxl_fn;
> > };
> >
> > +enum overwrite_state {
> > + SCM_OVERWRITE_IDLE = 0,
> > + SCM_OVERWRITE_BUSY,
> > + SCM_OVERWRITE_SUCCESS,
> > + SCM_OVERWRITE_FAILED
> > +};
> > +
> > struct scm_data {
> > struct device dev;
> > struct pci_dev *pdev;
> > @@ -116,6 +132,7 @@ struct scm_data {
> > void *metadata_addr;
> > struct command_metadata admin_command;
> > struct command_metadata ns_command;
> > + enum overwrite_state overwrite_state;
> > struct resource scm_res;
> > struct nd_region *nd_region;
> > struct eventfd_ctx *ev_ctx;
--
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819

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