On 21-02-10 08:55:57, Ben Widawsky wrote: > On 21-02-10 15:07:59, Jonathan Cameron wrote: > > On Wed, 10 Feb 2021 13:32:52 +0000 > > Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > > > > > On Tue, 9 Feb 2021 16:02:53 -0800 > > > Ben Widawsky <ben.widawsky@xxxxxxxxx> wrote: > > > > > > > Provide enough functionality to utilize the mailbox of a memory device. > > > > The mailbox is used to interact with the firmware running on the memory > > > > device. The flow is proven with one implemented command, "identify". > > > > Because the class code has already told the driver this is a memory > > > > device and the identify command is mandatory. > > > > > > > > CXL devices contain an array of capabilities that describe the > > > > interactions software can have with the device or firmware running on > > > > the device. A CXL compliant device must implement the device status and > > > > the mailbox capability. Additionally, a CXL compliant memory device must > > > > implement the memory device capability. Each of the capabilities can > > > > [will] provide an offset within the MMIO region for interacting with the > > > > CXL device. > > > > > > > > The capabilities tell the driver how to find and map the register space > > > > for CXL Memory Devices. The registers are required to utilize the CXL > > > > spec defined mailbox interface. The spec outlines two mailboxes, primary > > > > and secondary. The secondary mailbox is earmarked for system firmware, > > > > and not handled in this driver. > > > > > > > > Primary mailboxes are capable of generating an interrupt when submitting > > > > a background command. That implementation is saved for a later time. > > > > > > > > Link: https://www.computeexpresslink.org/download-the-specification > > > > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > > > Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > > > > > Hi Ben, > > > > > > > > > > +/** > > > > + * cxl_mem_mbox_send_cmd() - Send a mailbox command to a memory device. > > > > + * @cxlm: The CXL memory device to communicate with. > > > > + * @mbox_cmd: Command to send to the memory device. > > > > + * > > > > + * Context: Any context. Expects mbox_lock to be held. > > > > + * Return: -ETIMEDOUT if timeout occurred waiting for completion. 0 on success. > > > > + * Caller should check the return code in @mbox_cmd to make sure it > > > > + * succeeded. > > > > > > cxl_xfer_log() doesn't check mbox_cmd->return_code and for my test it currently > > > enters an infinite loop as a result. > > I meant to fix that. > > > > > > > I haven't checked other paths, but to my mind it is not a good idea to require > > > two levels of error checking - the example here proves how easy it is to forget > > > one. > > Demonstrably, you're correct. I think it would be good to have a kernel only > mbox command that does the error checking though. Let me type something up and > see how it looks. Hi Jonathan. What do you think of this? The bit I'm on the fence about is if I should validate output size too. I like the simplicity as it is, but it requires every caller to possibly check output size, which is kind of the same problem you're originally pointing out. diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c index 55c5f5a6023f..ad7b2077ab28 100644 --- a/drivers/cxl/mem.c +++ b/drivers/cxl/mem.c @@ -284,7 +284,7 @@ static void cxl_mem_mbox_timeout(struct cxl_mem *cxlm, } /** - * cxl_mem_mbox_send_cmd() - Send a mailbox command to a memory device. + * __cxl_mem_mbox_send_cmd() - Execute a mailbox command * @cxlm: The CXL memory device to communicate with. * @mbox_cmd: Command to send to the memory device. * @@ -296,7 +296,8 @@ static void cxl_mem_mbox_timeout(struct cxl_mem *cxlm, * This is a generic form of the CXL mailbox send command, thus the only I/O * operations used are cxl_read_mbox_reg(). Memory devices, and perhaps other * types of CXL devices may have further information available upon error - * conditions. + * conditions. Driver facilities wishing to send mailbox commands should use the + * wrapper command. * * The CXL spec allows for up to two mailboxes. The intention is for the primary * mailbox to be OS controlled and the secondary mailbox to be used by system @@ -304,8 +305,8 @@ static void cxl_mem_mbox_timeout(struct cxl_mem *cxlm, * not need to coordinate with each other. The driver only uses the primary * mailbox. */ -static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, - struct mbox_cmd *mbox_cmd) +static int __cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, + struct mbox_cmd *mbox_cmd) { void __iomem *payload = cxlm->mbox_regs + CXLDEV_MBOX_PAYLOAD_OFFSET; u64 cmd_reg, status_reg; @@ -469,6 +470,54 @@ static void cxl_mem_mbox_put(struct cxl_mem *cxlm) mutex_unlock(&cxlm->mbox_mutex); } +/** + * cxl_mem_mbox_send_cmd() - Send a mailbox command to a memory device. + * @cxlm: The CXL memory device to communicate with. + * @opcode: Opcode for the mailbox command. + * @in: The input payload for the mailbox command. + * @in_size: The length of the input payload + * @out: Caller allocated buffer for the output. + * + * Context: Any context. Will acquire and release mbox_mutex. + * Return: + * * %>=0 - Number of bytes returned in @out. + * * %-EBUSY - Couldn't acquire exclusive mailbox access. + * * %-EFAULT - Hardware error occurred. + * * %-ENXIO - Command completed, but device reported an error. + * + * Mailbox commands may execute successfully yet the device itself reported an + * error. While this distinction can be useful for commands from userspace, the + * kernel will often only care when both are successful. + * + * See __cxl_mem_mbox_send_cmd() + */ +static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, u16 opcode, u8 *in, + size_t in_size, u8 *out) +{ + struct mbox_cmd mbox_cmd = { + .opcode = opcode, + .payload_in = in, + .size_in = in_size, + .payload_out = out, + }; + int rc; + + rc = cxl_mem_mbox_get(cxlm); + if (rc) + return rc; + + rc = __cxl_mem_mbox_send_cmd(cxlm, &mbox_cmd); + cxl_mem_mbox_put(cxlm); + if (rc) + return rc; + + /* TODO: Map return code to proper kernel style errno */ + if (mbox_cmd.return_code != CXL_MBOX_SUCCESS) + return -ENXIO; + + return mbox_cmd.size_out; +} + /** * handle_mailbox_cmd_from_user() - Dispatch a mailbox command. * @cxlmd: The CXL memory device to communicate with. @@ -1380,33 +1429,18 @@ static int cxl_mem_identify(struct cxl_mem *cxlm) u8 poison_caps; u8 qos_telemetry_caps; } __packed id; - struct mbox_cmd mbox_cmd = { - .opcode = CXL_MBOX_OP_IDENTIFY, - .payload_out = &id, - .size_in = 0, - }; int rc; - /* Retrieve initial device memory map */ - rc = cxl_mem_mbox_get(cxlm); - if (rc) - return rc; - - rc = cxl_mem_mbox_send_cmd(cxlm, &mbox_cmd); - cxl_mem_mbox_put(cxlm); - if (rc) + rc = cxl_mem_mbox_send_cmd(cxlm, CXL_MBOX_OP_IDENTIFY, NULL, 0, + (u8 *)&id); + if (rc < 0) return rc; - /* TODO: Handle retry or reset responses from firmware. */ - if (mbox_cmd.return_code != CXL_MBOX_SUCCESS) { - dev_err(&cxlm->pdev->dev, "Mailbox command failed (%d)\n", - mbox_cmd.return_code); + if (rc < sizeof(id)) { + dev_err(&cxlm->pdev->dev, "Short identify data\n", return -ENXIO; } - if (mbox_cmd.size_out != sizeof(id)) - return -ENXIO; - /* * TODO: enumerate DPA map, as 'ram' and 'pmem' do not alias. * For now, only the capacity is exported in sysfs [snip]
