[PATCH crypto-2.6] crypto: ccp: add timeout support in the SEV command

* [PATCH crypto-2.6] crypto: ccp: add timeout support in the SEV command
       [not found] <1534367485-4386-1-git-send-email-brijesh.singh@amd.com>
@ 2018-08-15 21:11 ` Brijesh Singh
  2018-09-04  5:19   ` Herbert Xu
  2018-09-04  8:11   ` Borislav Petkov
  0 siblings, 2 replies; 7+ messages in thread
From: Brijesh Singh @ 2018-08-15 21:11 UTC (permalink / raw)
  To: linux-crypto
  Cc: thomas.lendacky, Brijesh Singh, Gary Hook, Herbert Xu, linux-kernel

Currently, the CCP driver assumes that the SEV command issued to the PSP
will always return (i.e. it will never hang).  But recently, firmware bugs
have shown that a command can hang.  Since of the SEV commands are used
in probe routines, this can cause boot hangs and/or loss of virtualization
capabilities.

To protect against firmware bugs, add a timeout in the SEV command
execution flow.  If a command does not complete within the specified
timeout then return -ETIMEOUT and stop the driver from executing any
further commands since the state of the SEV firmware is unknown.

Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gary Hook <Gary.Hook@amd.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 drivers/crypto/ccp/psp-dev.c | 46 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 5 deletions(-)

diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
index 218739b..72790d8 100644
--- a/drivers/crypto/ccp/psp-dev.c
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -38,6 +38,17 @@ static DEFINE_MUTEX(sev_cmd_mutex);
 static struct sev_misc_dev *misc_dev;
 static struct psp_device *psp_master;
 
+static int psp_cmd_timeout = 100;
+module_param(psp_cmd_timeout, int, 0644);
+MODULE_PARM_DESC(psp_cmd_timeout, " default timeout value, in seconds, for PSP commands");
+
+static int psp_probe_timeout = 5;
+module_param(psp_probe_timeout, int, 0644);
+MODULE_PARM_DESC(psp_probe_timeout, " default timeout value, in seconds, during PSP device probe");
+
+static bool psp_dead;
+static int psp_timeout;
+
 static struct psp_device *psp_alloc_struct(struct sp_device *sp)
 {
 	struct device *dev = sp->dev;
@@ -82,10 +93,19 @@ static irqreturn_t psp_irq_handler(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
-static void sev_wait_cmd_ioc(struct psp_device *psp, unsigned int *reg)
+static int sev_wait_cmd_ioc(struct psp_device *psp,
+			    unsigned int *reg, unsigned int timeout)
 {
-	wait_event(psp->sev_int_queue, psp->sev_int_rcvd);
+	int ret;
+
+	ret = wait_event_timeout(psp->sev_int_queue,
+			psp->sev_int_rcvd, timeout * HZ);
+	if (!ret)
+		return -ETIMEDOUT;
+
 	*reg = ioread32(psp->io_regs + psp->vdata->cmdresp_reg);
+
+	return 0;
 }
 
 static int sev_cmd_buffer_len(int cmd)
@@ -133,12 +153,15 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 	if (!psp)
 		return -ENODEV;
 
+	if (psp_dead)
+		return -EBUSY;
+
 	/* Get the physical address of the command buffer */
 	phys_lsb = data ? lower_32_bits(__psp_pa(data)) : 0;
 	phys_msb = data ? upper_32_bits(__psp_pa(data)) : 0;
 
-	dev_dbg(psp->dev, "sev command id %#x buffer 0x%08x%08x\n",
-		cmd, phys_msb, phys_lsb);
+	dev_dbg(psp->dev, "sev command id %#x buffer 0x%08x%08x timeout %us\n",
+		cmd, phys_msb, phys_lsb, psp_timeout);
 
 	print_hex_dump_debug("(in):  ", DUMP_PREFIX_OFFSET, 16, 2, data,
 			     sev_cmd_buffer_len(cmd), false);
@@ -154,7 +177,18 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 	iowrite32(reg, psp->io_regs + psp->vdata->cmdresp_reg);
 
 	/* wait for command completion */
-	sev_wait_cmd_ioc(psp, &reg);
+	ret = sev_wait_cmd_ioc(psp, &reg, psp_timeout);
+	if (ret) {
+		if (psp_ret)
+			*psp_ret = 0;
+
+		dev_err(psp->dev, "sev command %#x timed out, disabling PSP \n", cmd);
+		psp_dead = true;
+
+		return ret;
+	}
+
+	psp_timeout = psp_cmd_timeout;
 
 	if (psp_ret)
 		*psp_ret = reg & PSP_CMDRESP_ERR_MASK;
@@ -888,6 +922,8 @@ void psp_pci_init(void)
 
 	psp_master = sp->psp_data;
 
+	psp_timeout = psp_probe_timeout;
+
 	if (sev_get_api_version())
 		goto err;
 
-- 
2.7.4


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