platform/x86/dell: add buffer allocation/free functions for SMI calls

The dcdbas driver is used to call SMI handlers for both, dcdbas and
dell-smbios-smm. Both drivers allocate a buffer for communicating
with the SMI handler. The physical buffer address is then passed to
the called SMI handler via %ebx.

Unfortunately this doesn't work when running in Xen dom0, as the
physical address obtained via virt_to_phys() is only a guest physical
address, and not a machine physical address as needed by SMI.

The problem in dcdbas is easy to correct, as dcdbas is using
dma_alloc_coherent() for allocating the buffer, and the machine
physical address is available via the DMA address returned in the DMA
handle.

In order to avoid duplicating the buffer allocation code in
dell-smbios-smm, add a generic buffer allocation function to dcdbas
and use it for both drivers. This is especially fine regarding driver
dependencies, as dell-smbios-smm is already calling dcdbas to generate
the SMI request.

Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220318150950.16843-1-jgross@suse.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/dell/dcdbas.c

@@ -40,77 +40,90 @@
 
 static struct platform_device *dcdbas_pdev;
 
-static u8 *smi_data_buf;
-static dma_addr_t smi_data_buf_handle;
-static unsigned long smi_data_buf_size;
 static unsigned long max_smi_data_buf_size = MAX_SMI_DATA_BUF_SIZE;
-static u32 smi_data_buf_phys_addr;
 static DEFINE_MUTEX(smi_data_lock);
 static u8 *bios_buffer;
+static struct smi_buffer smi_buf;
 
 static unsigned int host_control_action;
 static unsigned int host_control_smi_type;
 static unsigned int host_control_on_shutdown;
 
 static bool wsmt_enabled;
 
+int dcdbas_smi_alloc(struct smi_buffer *smi_buffer, unsigned long size)
+{
+	smi_buffer->virt = dma_alloc_coherent(&dcdbas_pdev->dev, size,
+					      &smi_buffer->dma, GFP_KERNEL);
+	if (!smi_buffer->virt) {
+		dev_dbg(&dcdbas_pdev->dev,
+			"%s: failed to allocate memory size %lu\n",
+			__func__, size);
+		return -ENOMEM;
+	}
+	smi_buffer->size = size;
+
+	dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
+		__func__, (u32)smi_buffer->dma, smi_buffer->size);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dcdbas_smi_alloc);
+
+void dcdbas_smi_free(struct smi_buffer *smi_buffer)
+{
+	if (!smi_buffer->virt)
+		return;
+
+	dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
+		__func__, (u32)smi_buffer->dma, smi_buffer->size);
+	dma_free_coherent(&dcdbas_pdev->dev, smi_buffer->size,
+			  smi_buffer->virt, smi_buffer->dma);
+	smi_buffer->virt = NULL;
+	smi_buffer->dma = 0;
+	smi_buffer->size = 0;
+}
+EXPORT_SYMBOL_GPL(dcdbas_smi_free);
+
 /**
  * smi_data_buf_free: free SMI data buffer
  */
 static void smi_data_buf_free(void)
 {
-	if (!smi_data_buf || wsmt_enabled)
+	if (!smi_buf.virt || wsmt_enabled)
 		return;
 
-	dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
-		__func__, smi_data_buf_phys_addr, smi_data_buf_size);
-
-	dma_free_coherent(&dcdbas_pdev->dev, smi_data_buf_size, smi_data_buf,
-			  smi_data_buf_handle);
-	smi_data_buf = NULL;
-	smi_data_buf_handle = 0;
-	smi_data_buf_phys_addr = 0;
-	smi_data_buf_size = 0;
+	dcdbas_smi_free(&smi_buf);
 }
 
 /**
  * smi_data_buf_realloc: grow SMI data buffer if needed
  */
 static int smi_data_buf_realloc(unsigned long size)
 {
-	void *buf;
-	dma_addr_t handle;
+	struct smi_buffer tmp;
+	int ret;
 
-	if (smi_data_buf_size >= size)
+	if (smi_buf.size >= size)
 		return 0;
 
 	if (size > max_smi_data_buf_size)
 		return -EINVAL;
 
 	/* new buffer is needed */
-	buf = dma_alloc_coherent(&dcdbas_pdev->dev, size, &handle, GFP_KERNEL);
-	if (!buf) {
-		dev_dbg(&dcdbas_pdev->dev,
-			"%s: failed to allocate memory size %lu\n",
-			__func__, size);
-		return -ENOMEM;
-	}
-	/* memory zeroed by dma_alloc_coherent */
+	ret = dcdbas_smi_alloc(&tmp, size);
+	if (ret)
+		return ret;
 
-	if (smi_data_buf)
-		memcpy(buf, smi_data_buf, smi_data_buf_size);
+	/* memory zeroed by dma_alloc_coherent */
+	if (smi_buf.virt)
+		memcpy(tmp.virt, smi_buf.virt, smi_buf.size);
 
 	/* free any existing buffer */
 	smi_data_buf_free();
 
 	/* set up new buffer for use */
-	smi_data_buf = buf;
-	smi_data_buf_handle = handle;
-	smi_data_buf_phys_addr = (u32) virt_to_phys(buf);
-	smi_data_buf_size = size;
-
-	dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
-		__func__, smi_data_buf_phys_addr, smi_data_buf_size);
+	smi_buf = tmp;
 
 	return 0;
 }
@@ -119,14 +132,14 @@ static ssize_t smi_data_buf_phys_addr_show(struct device *dev,
 					   struct device_attribute *attr,
 					   char *buf)
 {
-	return sprintf(buf, "%x\n", smi_data_buf_phys_addr);
+	return sprintf(buf, "%x\n", (u32)smi_buf.dma);
 }
 
 static ssize_t smi_data_buf_size_show(struct device *dev,
 				      struct device_attribute *attr,
 				      char *buf)
 {
-	return sprintf(buf, "%lu\n", smi_data_buf_size);
+	return sprintf(buf, "%lu\n", smi_buf.size);
 }
 
 static ssize_t smi_data_buf_size_store(struct device *dev,
@@ -155,8 +168,8 @@ static ssize_t smi_data_read(struct file *filp, struct kobject *kobj,
 	ssize_t ret;
 
 	mutex_lock(&smi_data_lock);
-	ret = memory_read_from_buffer(buf, count, &pos, smi_data_buf,
-					smi_data_buf_size);
+	ret = memory_read_from_buffer(buf, count, &pos, smi_buf.virt,
+					smi_buf.size);
 	mutex_unlock(&smi_data_lock);
 	return ret;
 }
@@ -176,7 +189,7 @@ static ssize_t smi_data_write(struct file *filp, struct kobject *kobj,
 	if (ret)
 		goto out;
 
-	memcpy(smi_data_buf + pos, buf, count);
+	memcpy(smi_buf.virt + pos, buf, count);
 	ret = count;
 out:
 	mutex_unlock(&smi_data_lock);
@@ -307,11 +320,11 @@ static ssize_t smi_request_store(struct device *dev,
 
 	mutex_lock(&smi_data_lock);
 
-	if (smi_data_buf_size < sizeof(struct smi_cmd)) {
+	if (smi_buf.size < sizeof(struct smi_cmd)) {
 		ret = -ENODEV;
 		goto out;
 	}
-	smi_cmd = (struct smi_cmd *)smi_data_buf;
+	smi_cmd = (struct smi_cmd *)smi_buf.virt;
 
 	switch (val) {
 	case 2:
@@ -327,20 +340,20 @@ static ssize_t smi_request_store(struct device *dev,
 		 * Provide physical address of command buffer field within
 		 * the struct smi_cmd to BIOS.
 		 *
-		 * Because the address that smi_cmd (smi_data_buf) points to
+		 * Because the address that smi_cmd (smi_buf.virt) points to
 		 * will be from memremap() of a non-memory address if WSMT
 		 * is present, we can't use virt_to_phys() on smi_cmd, so
 		 * we have to use the physical address that was saved when
 		 * the virtual address for smi_cmd was received.
 		 */
-		smi_cmd->ebx = smi_data_buf_phys_addr +
+		smi_cmd->ebx = (u32)smi_buf.dma +
 				offsetof(struct smi_cmd, command_buffer);
 		ret = dcdbas_smi_request(smi_cmd);
 		if (!ret)
 			ret = count;
 		break;
 	case 0:
-		memset(smi_data_buf, 0, smi_data_buf_size);
+		memset(smi_buf.virt, 0, smi_buf.size);
 		ret = count;
 		break;
 	default:
@@ -356,7 +369,7 @@ static ssize_t smi_request_store(struct device *dev,
 /**
  * host_control_smi: generate host control SMI
  *
- * Caller must set up the host control command in smi_data_buf.
+ * Caller must set up the host control command in smi_buf.virt.
  */
 static int host_control_smi(void)
 {
@@ -367,14 +380,14 @@ static int host_control_smi(void)
 	s8 cmd_status;
 	u8 index;
 
-	apm_cmd = (struct apm_cmd *)smi_data_buf;
+	apm_cmd = (struct apm_cmd *)smi_buf.virt;
 	apm_cmd->status = ESM_STATUS_CMD_UNSUCCESSFUL;
 
 	switch (host_control_smi_type) {
 	case HC_SMITYPE_TYPE1:
 		spin_lock_irqsave(&rtc_lock, flags);
 		/* write SMI data buffer physical address */
-		data = (u8 *)&smi_data_buf_phys_addr;
+		data = (u8 *)&smi_buf.dma;
 		for (index = PE1300_CMOS_CMD_STRUCT_PTR;
 		     index < (PE1300_CMOS_CMD_STRUCT_PTR + 4);
 		     index++, data++) {
@@ -405,7 +418,7 @@ static int host_control_smi(void)
 	case HC_SMITYPE_TYPE3:
 		spin_lock_irqsave(&rtc_lock, flags);
 		/* write SMI data buffer physical address */
-		data = (u8 *)&smi_data_buf_phys_addr;
+		data = (u8 *)&smi_buf.dma;
 		for (index = PE1400_CMOS_CMD_STRUCT_PTR;
 		     index < (PE1400_CMOS_CMD_STRUCT_PTR + 4);
 		     index++, data++) {
@@ -450,7 +463,7 @@ static int host_control_smi(void)
  * This function is called by the driver after the system has
  * finished shutting down if the user application specified a
  * host control action to perform on shutdown.  It is safe to
- * use smi_data_buf at this point because the system has finished
+ * use smi_buf.virt at this point because the system has finished
  * shutting down and no userspace apps are running.
  */
 static void dcdbas_host_control(void)
@@ -464,18 +477,18 @@ static void dcdbas_host_control(void)
 	action = host_control_action;
 	host_control_action = HC_ACTION_NONE;
 
-	if (!smi_data_buf) {
+	if (!smi_buf.virt) {
 		dev_dbg(&dcdbas_pdev->dev, "%s: no SMI buffer\n", __func__);
 		return;
 	}
 
-	if (smi_data_buf_size < sizeof(struct apm_cmd)) {
+	if (smi_buf.size < sizeof(struct apm_cmd)) {
 		dev_dbg(&dcdbas_pdev->dev, "%s: SMI buffer too small\n",
 			__func__);
 		return;
 	}
 
-	apm_cmd = (struct apm_cmd *)smi_data_buf;
+	apm_cmd = (struct apm_cmd *)smi_buf.virt;
 
 	/* power off takes precedence */
 	if (action & HC_ACTION_HOST_CONTROL_POWEROFF) {
@@ -583,11 +596,11 @@ static int dcdbas_check_wsmt(void)
 		return -ENOMEM;
 	}
 
-	/* First 8 bytes is for a semaphore, not part of the smi_data_buf */
-	smi_data_buf_phys_addr = bios_buf_paddr + 8;
-	smi_data_buf = bios_buffer + 8;
-	smi_data_buf_size = remap_size - 8;
-	max_smi_data_buf_size = smi_data_buf_size;
+	/* First 8 bytes is for a semaphore, not part of the smi_buf.virt */
+	smi_buf.dma = bios_buf_paddr + 8;
+	smi_buf.virt = bios_buffer + 8;
+	smi_buf.size = remap_size - 8;
+	max_smi_data_buf_size = smi_buf.size;
 	wsmt_enabled = true;
 	dev_info(&dcdbas_pdev->dev,
 		 "WSMT found, using firmware-provided SMI buffer.\n");

drivers/platform/x86/dell/dcdbas.h

@@ -105,5 +105,14 @@ struct smm_eps_table {
 	u64 num_of_4k_pages;
 } __packed;
 
+struct smi_buffer {
+	u8 *virt;
+	unsigned long size;
+	dma_addr_t dma;
+};
+
+int dcdbas_smi_alloc(struct smi_buffer *smi_buffer, unsigned long size);
+void dcdbas_smi_free(struct smi_buffer *smi_buffer);
+
 #endif /* _DCDBAS_H_ */
 

drivers/platform/x86/dell/dell-smbios-smm.c

@@ -20,6 +20,7 @@
 
 static int da_command_address;
 static int da_command_code;
+static struct smi_buffer smi_buf;
 static struct calling_interface_buffer *buffer;
 static struct platform_device *platform_device;
 static DEFINE_MUTEX(smm_mutex);
@@ -57,7 +58,7 @@ static int dell_smbios_smm_call(struct calling_interface_buffer *input)
 	command.magic = SMI_CMD_MAGIC;
 	command.command_address = da_command_address;
 	command.command_code = da_command_code;
-	command.ebx = virt_to_phys(buffer);
+	command.ebx = smi_buf.dma;
 	command.ecx = 0x42534931;
 
 	mutex_lock(&smm_mutex);
@@ -101,9 +102,10 @@ int init_dell_smbios_smm(void)
 	 * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
 	 * is passed to SMI handler.
 	 */
-	buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);
-	if (!buffer)
-		return -ENOMEM;
+	ret = dcdbas_smi_alloc(&smi_buf, PAGE_SIZE);
+	if (ret)
+		return ret;
+	buffer = (void *)smi_buf.virt;
 
 	dmi_walk(find_cmd_address, NULL);
 
@@ -138,7 +140,7 @@ int init_dell_smbios_smm(void)
 
 fail_wsmt:
 fail_platform_device_alloc:
-	free_page((unsigned long)buffer);
+	dcdbas_smi_free(&smi_buf);
 	return ret;
 }
 
@@ -147,6 +149,6 @@ void exit_dell_smbios_smm(void)
 	if (platform_device) {
 		dell_smbios_unregister_device(&platform_device->dev);
 		platform_device_unregister(platform_device);
-		free_page((unsigned long)buffer);
+		dcdbas_smi_free(&smi_buf);
 	}
 }