[Patch v4 6/7] crypto/ccp: Register with fw_uploader and always fail

["Pratik R. Sampat" <prsampat@amd.com>]

In preparation for SEV-SNP DOWNLOAD_FIRMWARE_EX live firmware update
support, add an 'sev' firmware loader that always fails with EBUSY.

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Co-developed-by: Tycho Andersen (AMD) <tycho@kernel.org>
Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Signed-off-by: Pratik R. Sampat <prsampat@amd.com>
---
v3..v4:
* Collected Reviewed-by tags
* Cleanups for multiline error reporting - Tom
* Add FW_UPLOAD and FW_LOADER to CRYPTO_DEV_SP_PSP config- Shantanu
---
 drivers/crypto/ccp/Kconfig   |  2 +
 drivers/crypto/ccp/sev-dev.c | 72 ++++++++++++++++++++++++++++++++++++
 drivers/crypto/ccp/sev-dev.h |  2 +
 3 files changed, 76 insertions(+)

diff --git a/drivers/crypto/ccp/Kconfig b/drivers/crypto/ccp/Kconfig
index f16a0f611317..8544533a962a 100644
--- a/drivers/crypto/ccp/Kconfig
+++ b/drivers/crypto/ccp/Kconfig
@@ -40,6 +40,8 @@ config CRYPTO_DEV_SP_PSP
 	default y
 	depends on CRYPTO_DEV_CCP_DD && X86_64 && AMD_IOMMU
 	select PCI_TSM if PCI
+	select FW_LOADER
+	select FW_UPLOAD
 	help
 	 Provide support for the AMD Platform Security Processor (PSP).
 	 The PSP is a dedicated processor that provides support for key
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 76698a7a1a3c..e24c04956535 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -2212,6 +2212,72 @@ static int sev_update_firmware(struct device *dev)
 	return ret;
 }
 
+static enum fw_upload_err sev_fw_upload_prepare(struct fw_upload *fw_upload,
+						const u8 *data, u32 size)
+{
+	return FW_UPLOAD_ERR_NONE;
+}
+
+static enum fw_upload_err sev_fw_upload_write(struct fw_upload *fw_upload,
+					      const u8 *data, u32 offset,
+					      u32 size, u32 *written)
+{
+	return FW_UPLOAD_ERR_BUSY;
+}
+
+static enum fw_upload_err sev_fw_upload_poll_complete(struct fw_upload *fw_upload)
+{
+	return FW_UPLOAD_ERR_NONE;
+}
+
+static void sev_fw_upload_cancel(struct fw_upload *fw_upload)
+{
+	/* intentional no-op */
+}
+
+static const struct fw_upload_ops sev_fw_upload_ops = {
+	.prepare = sev_fw_upload_prepare,
+	.write = sev_fw_upload_write,
+	.poll_complete = sev_fw_upload_poll_complete,
+	.cancel = sev_fw_upload_cancel,
+};
+
+/* Serializes registration and unregistration of sev->fwl */
+static DEFINE_MUTEX(sev_fwl_lock);
+
+static void register_sev_fw_uploader(struct sev_device *sev)
+{
+	struct fw_upload *fwl;
+
+	guard(mutex)(&sev_fwl_lock);
+
+	/*
+	 * The interface only drives DLFW_EX, which is an SNP command, so do not
+	 * advertise it where SNP is unavailable or the interface already exists
+	 */
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP) || sev->fwl)
+		return;
+
+	fwl = firmware_upload_register(sev->dev, "sev", &sev_fw_upload_ops, sev);
+	if (IS_ERR(fwl)) {
+		dev_err(sev->dev, "SEV firmware upload registration failure: %ld\n", PTR_ERR(fwl));
+		return;
+	}
+
+	sev->fwl = fwl;
+}
+
+static void unregister_sev_fw_uploader(struct sev_device *sev)
+{
+	guard(mutex)(&sev_fwl_lock);
+
+	if (!sev->fwl)
+		return;
+
+	firmware_upload_unregister(sev->fwl);
+	sev->fwl = NULL;
+}
+
 static int __sev_snp_shutdown_locked(int *error, bool panic)
 {
 	struct psp_device *psp = psp_master;
@@ -3018,6 +3084,8 @@ void sev_dev_destroy(struct psp_device *psp)
 	if (!sev)
 		return;
 
+	unregister_sev_fw_uploader(sev);
+
 	sev_firmware_shutdown(sev);
 
 	if (sev->misc)
@@ -3081,6 +3149,8 @@ void sev_pci_init(void)
 			 api_major, api_minor, build,
 			 sev->api_major, sev->api_minor, sev->build);
 
+	register_sev_fw_uploader(sev);
+
 	return;
 
 err:
@@ -3096,6 +3166,8 @@ void sev_pci_exit(void)
 	if (!sev)
 		return;
 
+	unregister_sev_fw_uploader(sev);
+
 	sev_firmware_shutdown(sev);
 }
 
diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
index d5e596606def..7ec692e2147e 100644
--- a/drivers/crypto/ccp/sev-dev.h
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -69,6 +69,8 @@ struct sev_device {
 
 	struct tsm_dev *tsmdev;
 	struct sev_tio_status *tio_status;
+
+	struct fw_upload *fwl;
 };
 
 int sev_dev_init(struct psp_device *psp);
-- 
2.43.0