Re: [PATCH 4/4] tools/testing/cxl: add firmware update emulation to CXL memdevs

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Thu, 18 May 2023 20:01:18 -0700
Alison Schofield <alison.schofield@intel.com> wrote:

> On Thu, May 11, 2023 at 05:18:16PM +0100, Jonathan Cameron wrote:
> > On Fri, 21 Apr 2023 21:09:28 -0600
> > Vishal Verma <vishal.l.verma@intel.com> wrote:
> >   
> > > Add emulation for the 'Get FW Info', 'Transfer FW', and 'Activate FW'
> > > CXL mailbox commands to the cxl_test emulated memdevs to enable
> > > end-to-end unit testing of a firmware update flow. For now, only
> > > advertise an 'offline activation' capability as that is all the CXL
> > > memdev driver currently implements.
> > > 
> > > Add some canned values for the serial number fields, and create a
> > > platform device sysfs knob to calculate the sha256sum of the firmware
> > > image that was received, so a unit test can compare it with the original
> > > file that was uploaded.
> > > 
> > > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>  
> > Hi Vishal,
> > 
> > A few trivial comments inline,
> > 
> > Thanks,
> > 
> > Jonathan
> >   
> > > ---
> > >  tools/testing/cxl/test/mem.c | 191 +++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 191 insertions(+)
> > > 
> > > diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
> > > index 9263b04d35f7..bc99cc673550 100644
> > > --- a/tools/testing/cxl/test/mem.c
> > > +++ b/tools/testing/cxl/test/mem.c
> > > @@ -7,11 +7,14 @@
> > >  #include <linux/delay.h>
> > >  #include <linux/sizes.h>
> > >  #include <linux/bits.h>
> > > +#include <crypto/hash.h>
> > >  #include <cxlmem.h>
> > >  
> > >  #include "trace.h"
> > >  
> > >  #define LSA_SIZE SZ_128K
> > > +#define FW_SIZE SZ_64M
> > > +#define FW_SLOTS 3
> > >  #define DEV_SIZE SZ_2G
> > >  #define EFFECT(x) (1U << x)
> > >  
> > > @@ -40,6 +43,18 @@ static struct cxl_cel_entry mock_cel[] = {
> > >  		.opcode = cpu_to_le16(CXL_MBOX_OP_GET_HEALTH_INFO),
> > >  		.effect = cpu_to_le16(0),
> > >  	},
> > > +	{
> > > +		.opcode = cpu_to_le16(CXL_MBOX_OP_GET_FW_INFO),
> > > +		.effect = cpu_to_le16(0),
> > > +	},
> > > +	{
> > > +		.opcode = cpu_to_le16(CXL_MBOX_OP_TRANSFER_FW),
> > > +		.effect = cpu_to_le16(EFFECT(0) | EFFECT(6)),  
> > 
> > Beginning to feel like some defines for each effect might be worth
> > adding.
> >   
> > > +	},
> > > +	{
> > > +		.opcode = cpu_to_le16(CXL_MBOX_OP_ACTIVATE_FW),
> > > +		.effect = cpu_to_le16(EFFECT(0) | EFFECT(1)),
> > > +	},
> > >  };  
> > 
> > ...
> >   
> > > +static int mock_transfer_fw(struct cxl_dev_state *cxlds,
> > > +			    struct cxl_mbox_cmd *cmd)
> > > +{
> > > +	struct cxl_mbox_transfer_fw *transfer = cmd->payload_in;
> > > +	struct cxl_mockmem_data *mdata = dev_get_drvdata(cxlds->dev);
> > > +	void *fw = mdata->fw;
> > > +	size_t offset, length;
> > > +
> > > +	offset = le32_to_cpu(transfer->offset) * CXL_FW_TRANSFER_OFFSET_ALIGN;
> > > +	length = cmd->size_in - sizeof(*transfer);
> > > +	if (offset + length > FW_SIZE)
> > > +		return -EINVAL;
> > > +
> > > +	switch (transfer->action) {
> > > +	case CXL_FW_TRANSFER_ACTION_FULL:
> > > +		if (offset != 0)
> > > +			return -EINVAL;
> > > +		fallthrough;
> > > +	case CXL_FW_TRANSFER_ACTION_END:
> > > +		if (transfer->slot == 0 || transfer->slot > FW_SLOTS)
> > > +			return -EINVAL;
> > > +		mdata->fw_size = offset + length;
> > > +		break;
> > > +	case CXL_FW_TRANSFER_ACTION_START:
> > > +	case CXL_FW_TRANSFER_ACTION_CONTINUE:
> > > +	case CXL_FW_TRANSFER_ACTION_ABORT:
> > > +		break;
> > > +	default:
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	memcpy(fw + offset, &transfer->data[0], length);  
> > 
> > Slight preference for transfer->data
> >   
> 
> What's the story behind that Jonathan? 
> I imagined kernel developers leaned towards the explicit.

Meh.  In my head it's copying beyond end of that particular
element, and transfer->data conveys that 'potential' better.  Others
may have different opinions.

I've never seen a hard and fast rule on this one...

Jonathan

> 
> Alison
> 
> 
> > > +	return 0;
> > > +}
> > > +  
> > 
> > ...
> >   
> > > +static int do_sha256(u8 *data, unsigned int length, u8 *hash)  
> > 
> > Can't use the one in include/crypto/sha2.h?  Don't think anyone really
> > cares about extreme performance here.
> >   
> > > +{
> > > +	struct crypto_shash *alg;
> > > +	struct sdesc *sdesc;
> > > +	size_t size;
> > > +	int rc;
> > > +
> > > +	alg = crypto_alloc_shash("sha256", 0, 0);
> > > +	if (IS_ERR(alg))
> > > +		return PTR_ERR(alg);
> > > +
> > > +	size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
> > > +	sdesc = kzalloc(size, GFP_KERNEL);
> > > +	if (!sdesc) {
> > > +		rc = -ENOMEM;
> > > +		goto out_shash;
> > > +	}
> > > +
> > > +	sdesc->shash.tfm = alg;
> > > +	rc = crypto_shash_digest(&sdesc->shash, data, length, hash);
> > > +
> > > +	kfree(sdesc);
> > > +out_shash:
> > > +	crypto_free_shash(alg);
> > > +	return rc;
> > > +}
> > > +
> > > +#define CHECKSUM_SIZE 32
> > > +
> > > +static ssize_t fw_buf_checksum_show(struct device *dev,
> > > +				    struct device_attribute *attr, char *buf)
> > > +{
> > > +	struct cxl_mockmem_data *mdata = dev_get_drvdata(dev);
> > > +	unsigned char *hstr, *hptr;
> > > +	u8 hash[CHECKSUM_SIZE];
> > > +	ssize_t written = 0;
> > > +	int i, rc;
> > > +
> > > +	rc = do_sha256(mdata->fw, mdata->fw_size, &hash[0]);
> > > +	if (rc) {
> > > +		dev_err(dev, "error calculating checksum: %d\n", rc);
> > > +		goto out_free;
> > > +	}
> > > +
> > > +	hstr = kzalloc((CHECKSUM_SIZE * 2) + 1, GFP_KERNEL);
> > > +	if (!hstr)
> > > +		return -ENOMEM;
> > > +
> > > +	hptr = hstr;
> > > +	for (i = 0; i < CHECKSUM_SIZE; i++)
> > > +		hptr += sprintf(hptr, "%02x", hash[i]);
> > > +
> > > +	written = sysfs_emit(buf, "%s\n", hstr);
> > > +
> > > +out_free:
> > > +	kfree(hstr);
> > > +	return written;
> > > +}
> > > +
> > > +static DEVICE_ATTR_RO(fw_buf_checksum);
> > > +
> > >  static struct attribute *cxl_mock_mem_attrs[] = {
> > >  	&dev_attr_security_lock.attr,
> > >  	&dev_attr_event_trigger.attr,
> > > +	&dev_attr_fw_buf_checksum.attr,
> > >  	NULL
> > >  };
> > >  ATTRIBUTE_GROUPS(cxl_mock_mem);
> > >   
> >