On reception of a completion interrupt the SMT memory area is accessed to
retrieve the message header at first and then, if the message sequence
number identifies a transaction which is still pending, the related
payload is fetched too.
When an SCMI command times out the channel ownership remains with the
platform until eventually a late reply is received and, as a consequence,
any further transmission attempt remains pending, waiting for the channel
to be relinquished by the platform.
Once that late reply is received the channel ownership is given back
to the agent and any pending request is then allowed to proceed and
overwrite the SMT area of the just delivered late reply; then the wait for
the reply to the new request starts.
It has been observed that the spurious IRQ related to the late reply can
be wrongly associated with the freshly enqueued request: when that happens
the SCMI stack in-flight lookup procedure is fooled by the fact that the
message header now present in the SMT area is related to the new pending
transaction, even though the real reply has still to arrive.
This race-condition on the A2P channel can be detected by looking at the
channel status bits: a genuine reply from the platform will have set the
channel free bit before triggering the completion IRQ.
Add a consistency check to validate such condition in the A2P ISR.
Reported-by: Xinglong Yang <[email protected]>
Closes: https://lore.kernel.org/all/PUZPR06MB54981E6FA00D82BFDBB864FBF08DA@PUZPR06MB5498.apcprd06.prod.outlook.com/
Fixes: 5c8a47a5a91d ("firmware: arm_scmi: Make scmi core independent of the transport type")
CC: [email protected] # 5.15+
Signed-off-by: Cristian Marussi <[email protected]>
---
drivers/firmware/arm_scmi/common.h | 1 +
drivers/firmware/arm_scmi/mailbox.c | 14 ++++++++++++++
drivers/firmware/arm_scmi/shmem.c | 6 ++++++
3 files changed, 21 insertions(+)
diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 3b7c68a11fd0..0956c2443840 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -329,6 +329,7 @@ void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem);
bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
struct scmi_xfer *xfer);
+bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem);
/* declarations for message passing transports */
struct scmi_msg_payld;
diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c
index 19246ed1f01f..b8d470417e8f 100644
--- a/drivers/firmware/arm_scmi/mailbox.c
+++ b/drivers/firmware/arm_scmi/mailbox.c
@@ -45,6 +45,20 @@ static void rx_callback(struct mbox_client *cl, void *m)
{
struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
+ /*
+ * An A2P IRQ is NOT valid when received while the platform still has
+ * the ownership of the channel, because the platform at first releases
+ * the SMT channel and then sends the completion interrupt.
+ *
+ * This addresses a possible race condition in which a spurious IRQ from
+ * a previous timed-out reply which arrived late could be wrongly
+ * associated with the next pending transaction.
+ */
+ if (cl->knows_txdone && !shmem_channel_free(smbox->shmem)) {
+ dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
+ return;
+ }
+
scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem), NULL);
}
diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c
index 87b4f4d35f06..517d52fb3bcb 100644
--- a/drivers/firmware/arm_scmi/shmem.c
+++ b/drivers/firmware/arm_scmi/shmem.c
@@ -122,3 +122,9 @@ bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
(SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
}
+
+bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem)
+{
+ return (ioread32(&shmem->channel_status) &
+ SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
+}
--
2.34.1
Hi, Cristian
This patch successfully solves the bug.
From: Cristian Marussi <[email protected]> Sent: Thursday, December 21, 2023 1:21 AM
> On reception of a completion interrupt the SMT memory area is accessed to
> retrieve the message header at first and then, if the message sequence
> number identifies a transaction which is still pending, the related
> payload is fetched too.
>
> When an SCMI command times out the channel ownership remains with the
> platform until eventually a late reply is received and, as a consequence,
> any further transmission attempt remains pending, waiting for the channel
> to be relinquished by the platform.
>
> Once that late reply is received the channel ownership is given back
> to the agent and any pending request is then allowed to proceed and
> overwrite the SMT area of the just delivered late reply; then the wait for
> the reply to the new request starts.
>
> It has been observed that the spurious IRQ related to the late reply can
> be wrongly associated with the freshly enqueued request: when that
> happens
> the SCMI stack in-flight lookup procedure is fooled by the fact that the
> message header now present in the SMT area is related to the new pending
> transaction, even though the real reply has still to arrive.
>
> This race-condition on the A2P channel can be detected by looking at the
> channel status bits: a genuine reply from the platform will have set the
> channel free bit before triggering the completion IRQ.
>
> Add a consistency check to validate such condition in the A2P ISR.
>
> Reported-by: Xinglong Yang <[email protected]>
> Closes:
> https://lore.k/
> ernel.org%2Fall%2FPUZPR06MB54981E6FA00D82BFDBB864FBF08DA%40PUZP
> R06MB5498.apcprd06.prod.outlook.com%2F&data=05%7C02%7Cxinglong.ya
> ng%40cixtech.com%7C669e9ff5e6764a77791208dc01801b8e%7C0409f77ae53
> d4d23943eccade7cb4811%7C1%7C0%7C638386896955072826%7CUnknown%
> 7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haW
> wiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=T1DOD7KfY%2FJNJHacHtX
> d5wcfde%2Fd5UDqGvyW4vuYwYU%3D&reserved=0
> Fixes: 5c8a47a5a91d ("firmware: arm_scmi: Make scmi core independent of
> the transport type")
> CC: [email protected] # 5.15+
> Signed-off-by: Cristian Marussi <[email protected]>
> ---
> drivers/firmware/arm_scmi/common.h | 1 +
> drivers/firmware/arm_scmi/mailbox.c | 14 ++++++++++++++
> drivers/firmware/arm_scmi/shmem.c | 6 ++++++
> 3 files changed, 21 insertions(+)
>
> diff --git a/drivers/firmware/arm_scmi/common.h
> b/drivers/firmware/arm_scmi/common.h
> index 3b7c68a11fd0..0956c2443840 100644
> --- a/drivers/firmware/arm_scmi/common.h
> +++ b/drivers/firmware/arm_scmi/common.h
> @@ -329,6 +329,7 @@ void shmem_fetch_notification(struct
> scmi_shared_mem __iomem *shmem,
> void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem);
> bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
> struct scmi_xfer *xfer);
> +bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem);
>
> /* declarations for message passing transports */
> struct scmi_msg_payld;
> diff --git a/drivers/firmware/arm_scmi/mailbox.c
> b/drivers/firmware/arm_scmi/mailbox.c
> index 19246ed1f01f..b8d470417e8f 100644
> --- a/drivers/firmware/arm_scmi/mailbox.c
> +++ b/drivers/firmware/arm_scmi/mailbox.c
> @@ -45,6 +45,20 @@ static void rx_callback(struct mbox_client *cl, void *m)
> {
> struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
>
> + /*
> + * An A2P IRQ is NOT valid when received while the platform still has
> + * the ownership of the channel, because the platform at first releases
> + * the SMT channel and then sends the completion interrupt.
> + *
> + * This addresses a possible race condition in which a spurious IRQ from
> + * a previous timed-out reply which arrived late could be wrongly
> + * associated with the next pending transaction.
> + */
> + if (cl->knows_txdone && !shmem_channel_free(smbox->shmem)) {
> + dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
> + return;
> + }
> +
> scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem),
> NULL);
> }
>
> diff --git a/drivers/firmware/arm_scmi/shmem.c
> b/drivers/firmware/arm_scmi/shmem.c
> index 87b4f4d35f06..517d52fb3bcb 100644
> --- a/drivers/firmware/arm_scmi/shmem.c
> +++ b/drivers/firmware/arm_scmi/shmem.c
> @@ -122,3 +122,9 @@ bool shmem_poll_done(struct scmi_shared_mem
> __iomem *shmem,
> (SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
> SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
> }
> +
> +bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem)
> +{
> + return (ioread32(&shmem->channel_status) &
> + SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
> +}
> --
> 2.34.1
Thanks,
Xinglong
On Thu, Dec 21, 2023 at 10:31:29AM +0000, Xinglong Yang wrote:
> Hi, Cristian
>
> This patch successfully solves the bug.
>
Hi Xinglong,
thanks for reporting and testing !
Cristian
> From: Cristian Marussi <[email protected]> Sent: Thursday, December 21, 2023 1:21 AM
> > On reception of a completion interrupt the SMT memory area is accessed to
> > retrieve the message header at first and then, if the message sequence
> > number identifies a transaction which is still pending, the related
> > payload is fetched too.
> >
> > When an SCMI command times out the channel ownership remains with the
> > platform until eventually a late reply is received and, as a consequence,
> > any further transmission attempt remains pending, waiting for the channel
> > to be relinquished by the platform.
> >
> > Once that late reply is received the channel ownership is given back
> > to the agent and any pending request is then allowed to proceed and
> > overwrite the SMT area of the just delivered late reply; then the wait for
> > the reply to the new request starts.
> >
> > It has been observed that the spurious IRQ related to the late reply can
> > be wrongly associated with the freshly enqueued request: when that
> > happens
> > the SCMI stack in-flight lookup procedure is fooled by the fact that the
> > message header now present in the SMT area is related to the new pending
> > transaction, even though the real reply has still to arrive.
> >
> > This race-condition on the A2P channel can be detected by looking at the
> > channel status bits: a genuine reply from the platform will have set the
> > channel free bit before triggering the completion IRQ.
> >
> > Add a consistency check to validate such condition in the A2P ISR.
> >
> > Reported-by: Xinglong Yang <[email protected]>
> > Closes:
> > https://lore.k/
> > ernel.org%2Fall%2FPUZPR06MB54981E6FA00D82BFDBB864FBF08DA%40PUZP
> > R06MB5498.apcprd06.prod.outlook.com%2F&data=05%7C02%7Cxinglong.ya
> > ng%40cixtech.com%7C669e9ff5e6764a77791208dc01801b8e%7C0409f77ae53
> > d4d23943eccade7cb4811%7C1%7C0%7C638386896955072826%7CUnknown%
> > 7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haW
> > wiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=T1DOD7KfY%2FJNJHacHtX
> > d5wcfde%2Fd5UDqGvyW4vuYwYU%3D&reserved=0
> > Fixes: 5c8a47a5a91d ("firmware: arm_scmi: Make scmi core independent of
> > the transport type")
> > CC: [email protected] # 5.15+
> > Signed-off-by: Cristian Marussi <[email protected]>
> > ---
> > drivers/firmware/arm_scmi/common.h | 1 +
> > drivers/firmware/arm_scmi/mailbox.c | 14 ++++++++++++++
> > drivers/firmware/arm_scmi/shmem.c | 6 ++++++
> > 3 files changed, 21 insertions(+)
> >
> > diff --git a/drivers/firmware/arm_scmi/common.h
> > b/drivers/firmware/arm_scmi/common.h
> > index 3b7c68a11fd0..0956c2443840 100644
> > --- a/drivers/firmware/arm_scmi/common.h
> > +++ b/drivers/firmware/arm_scmi/common.h
> > @@ -329,6 +329,7 @@ void shmem_fetch_notification(struct
> > scmi_shared_mem __iomem *shmem,
> > void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem);
> > bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
> > struct scmi_xfer *xfer);
> > +bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem);
> >
> > /* declarations for message passing transports */
> > struct scmi_msg_payld;
> > diff --git a/drivers/firmware/arm_scmi/mailbox.c
> > b/drivers/firmware/arm_scmi/mailbox.c
> > index 19246ed1f01f..b8d470417e8f 100644
> > --- a/drivers/firmware/arm_scmi/mailbox.c
> > +++ b/drivers/firmware/arm_scmi/mailbox.c
> > @@ -45,6 +45,20 @@ static void rx_callback(struct mbox_client *cl, void *m)
> > {
> > struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
> >
> > + /*
> > + * An A2P IRQ is NOT valid when received while the platform still has
> > + * the ownership of the channel, because the platform at first releases
> > + * the SMT channel and then sends the completion interrupt.
> > + *
> > + * This addresses a possible race condition in which a spurious IRQ from
> > + * a previous timed-out reply which arrived late could be wrongly
> > + * associated with the next pending transaction.
> > + */
> > + if (cl->knows_txdone && !shmem_channel_free(smbox->shmem)) {
> > + dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
> > + return;
> > + }
> > +
> > scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem),
> > NULL);
> > }
> >
> > diff --git a/drivers/firmware/arm_scmi/shmem.c
> > b/drivers/firmware/arm_scmi/shmem.c
> > index 87b4f4d35f06..517d52fb3bcb 100644
> > --- a/drivers/firmware/arm_scmi/shmem.c
> > +++ b/drivers/firmware/arm_scmi/shmem.c
> > @@ -122,3 +122,9 @@ bool shmem_poll_done(struct scmi_shared_mem
> > __iomem *shmem,
> > (SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
> > SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
> > }
> > +
> > +bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem)
> > +{
> > + return (ioread32(&shmem->channel_status) &
> > + SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
> > +}
> > --
> > 2.34.1
>
> Thanks,
> Xinglong
>
> _______________________________________________
> linux-arm-kernel mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Thu, Dec 21, 2023 at 10:31:29AM +0000, Xinglong Yang wrote:
> Hi, Cristian
>
> This patch successfully solves the bug.
>
I take this as:
Tested-by: Xinglong Yang <[email protected]>
Please shout if you don't imply that.
--
Regards,
Sudeep
It is ok.
From: Sudeep Holla <[email protected]> Sent: Thursday, December 21, 2023 6:52 PM
> On Thu, Dec 21, 2023 at 10:31:29AM +0000, Xinglong Yang wrote:
> > Hi, Cristian
> >
> > This patch successfully solves the bug.
> >
>
> I take this as:
>
> Tested-by: Xinglong Yang <[email protected]>
>
> Please shout if you don't imply that.
>
> --
> Regards,
> Sudeep
Thanks,
Xinglong
On Wed, 20 Dec 2023 17:21:12 +0000, Cristian Marussi wrote:
> On reception of a completion interrupt the SMT memory area is accessed to
> retrieve the message header at first and then, if the message sequence
> number identifies a transaction which is still pending, the related
> payload is fetched too.
>
> When an SCMI command times out the channel ownership remains with the
> platform until eventually a late reply is received and, as a consequence,
> any further transmission attempt remains pending, waiting for the channel
> to be relinquished by the platform.
>
> [...]
Applied to sudeep.holla/linux (for-next/scmi/fixes), thanks!
[1/1] firmware: arm_scmi: Check Mailbox/SMT channel for consistency
https://git.kernel.org/sudeep.holla/c/437a310b2224
--
Regards,
Sudeep