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SubjectRe: [PATCH crypto-2.6] crypto: ccp: add timeout support in the SEV command
On Wed, Aug 15, 2018 at 04:11:25PM -0500, Brijesh Singh wrote:
> 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");

Just a question: what prevents the user from supplying non-sensical
values here?

I think we should clamp them to only allowed values because I don't want
to be debugging some strange bugs due to that.

> +
> +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);

Align args at opening brace.

> + 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);
^

Trailing space.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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