Re: [PATCH v2] bus: mhi: host: Add tracing support
From: Jeffrey Hugo
Date: Fri Oct 27 2023 - 11:30:15 EST
On 10/23/2023 1:11 AM, Krishna Chaitanya Chundru wrote:
On 10/20/2023 8:33 PM, Jeffrey Hugo wrote:
On 10/13/2023 3:52 AM, Krishna chaitanya chundru wrote:
This change adds ftrace support for following functions which
helps in debugging the issues when there is Channel state & MHI
state change and also when we receive data and control events:
1. mhi_intvec_threaded_handler
2. mhi_process_data_event_ring
3. mhi_process_ctrl_ev_ring
4. mhi_gen_tre
5. mhi_update_channel_state
6. mhi_tryset_pm_state
7. mhi_pm_st_worker
Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
---
Changes in v2:
- Passing the raw state into the trace event and using
__print_symbolic() as suggested by bjorn.
- Change mhi_pm_st_worker to mhi_pm_st_transition as suggested by bjorn.
- Fixed the kernel test rebot issues.
- Link to v1:
https://lore.kernel.org/r/20231005-ftrace_support-v1-1-23a2f394fa49@xxxxxxxxxxx
---
MAINTAINERS | 1 +
drivers/bus/mhi/host/init.c | 3 +
drivers/bus/mhi/host/internal.h | 1 +
drivers/bus/mhi/host/main.c | 32 +++--
drivers/bus/mhi/host/pm.c | 6 +-
include/trace/events/mhi_host.h | 287
++++++++++++++++++++++++++++++++++++++++
6 files changed, 317 insertions(+), 13 deletions(-)
diff --git a/MAINTAINERS b/MAINTAINERS
index 35977b269d5e..4339c668a6ab 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13862,6 +13862,7 @@ F: Documentation/mhi/
F: drivers/bus/mhi/
F: drivers/pci/endpoint/functions/pci-epf-mhi.c
F: include/linux/mhi.h
+F: include/trace/events/mhi_host.h
MICROBLAZE ARCHITECTURE
M: Michal Simek <monstr@xxxxxxxxx>
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index f78aefd2d7a3..3afa90a204fd 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -20,6 +20,9 @@
#include <linux/wait.h>
#include "internal.h"
+#define CREATE_TRACE_POINTS
+#include <trace/events/mhi_host.h>
This feels redundant to me. A few lines ago we included internal.h,
and internal.h includes trace/events/mhi_host.h
As Steve mentioned, this is mandatory step for creating trace points &
trace events.
I understand this creates the trace points, and that needs to be done in
C code. It dtill seems redundant because we are including the header
twice (and I am aware trace has the special multi-header read
functionality for this).
The duplicate include still feels weird, but I have not come up with a
better way to structure this.
+
static DEFINE_IDA(mhi_controller_ida);
const char * const mhi_ee_str[MHI_EE_MAX] = {
diff --git a/drivers/bus/mhi/host/internal.h
b/drivers/bus/mhi/host/internal.h
index 2e139e76de4c..a80a317a59a9 100644
--- a/drivers/bus/mhi/host/internal.h
+++ b/drivers/bus/mhi/host/internal.h
@@ -7,6 +7,7 @@
#ifndef _MHI_INT_H
#define _MHI_INT_H
+#include <trace/events/mhi_host.h>
#include "../common.h"
extern struct bus_type mhi_bus_type;
diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index dcf627b36e82..fcdb728ba49f 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -246,6 +246,11 @@ static void *mhi_to_virtual(struct mhi_ring
*ring, dma_addr_t addr)
return (addr - ring->iommu_base) + ring->base;
}
+dma_addr_t mhi_to_physical(struct mhi_ring *ring, void *addr)
+{
+ return (addr - ring->base) + ring->iommu_base;
+}
This seems to be poorly named since we are using the iommu_base which
suggests we are converting to an IOVA.
Why do we need this though? This seems like it might be a security
issue, or at the very least, not preferred, and I'm struggling to
figure out what value this provides to you are I when looking at the log.
I will rename the function to reflect it is converting to IOVA.
We MHI TRE we write the IOVA address, to correlate between TRE events in
the MHI ring and event we are processing we want to log the IOVA address.
As we are logging only IOVA address which is provided in the devicetree
and not the original physical address we are not expecting any security
issues here.
Correct me if I was wrong.
The IOVA is not provided by DT, it is a runtime allocated value provided
by the IOMMU, if present. If not present, then it is a physical address.
Remember, x86 does not use devicetree.
While the IOVA (with an iommu) is not technically a physical address,
but is treated as such by the device. I can imagine an attacker doing
bad things if they get a hold of the value.
Still, you haven't indicated why this is useful.
+
static void mhi_add_ring_element(struct mhi_controller *mhi_cntrl,
struct mhi_ring *ring)
{
@@ -491,11 +496,9 @@ irqreturn_t mhi_intvec_threaded_handler(int
irq_number, void *priv)
state = mhi_get_mhi_state(mhi_cntrl);
ee = mhi_get_exec_env(mhi_cntrl);
- dev_dbg(dev, "local ee: %s state: %s device ee: %s state: %s\n",
- TO_MHI_EXEC_STR(mhi_cntrl->ee),
- mhi_state_str(mhi_cntrl->dev_state),
- TO_MHI_EXEC_STR(ee), mhi_state_str(state));
+ trace_mhi_intvec_threaded_handler(mhi_cntrl->mhi_dev->name,
mhi_cntrl->ee,
+ mhi_cntrl->dev_state, ee, state);
Why are we removing the debug message when adding this trace? The
commit text doesn't say. (Looks like you do this several times,
assume this comment applies to all isntances)
I will add this in the commit text in my next patch.
Just a query is recommended to keep both debug message and trace events.
If yes we will not remove the debug messages.
I think it would be preferred to have one mechanism or the other, not
both. It seems like you are doing an incomplete conversion.
if (state == MHI_STATE_SYS_ERR) {
dev_dbg(dev, "System error detected\n");
pm_state = mhi_tryset_pm_state(mhi_cntrl,
@@ -832,6 +835,12 @@ int mhi_process_ctrl_ev_ring(struct
mhi_controller *mhi_cntrl,
while (dev_rp != local_rp) {
enum mhi_pkt_type type = MHI_TRE_GET_EV_TYPE(local_rp);
+ trace_mhi_process_ctrl_ev_ring(mhi_cntrl->mhi_dev->name,
+ mhi_to_physical(ev_ring, local_rp),
+ local_rp->ptr, local_rp->dword[0],
+ local_rp->dword[1],
+ MHI_TRE_GET_EV_STATE(local_rp));
Why not just pass in the local_rp as a single parameter and have the
trace implementation decode it? (Looks like you do this several
times, assume this comment applies to all isntances)
MHI_TRE_GET_EV_STATE definition is present in drivers/bus/mhi/common.h
which is common for both EP & MHI driver.
If we keep this macro definition again in mhi_host.h it will be
redundant one.
What is wrong with including the right header over in the trace to get
the definition? I didn't ask for it to be redefined.
If the struct definition for local_rp changes, it will probably break
this, which will require changes to the definition and use of
trace_mhi_process_ctrl_ev_ring(). If trace_mhi_process_ctrl_ev_ring()
just takes the struct and decodes it, the decode logic just needs to be
updated (in one place) when the struct definition changes.
And we are only using this way only for this trace log. So we are using
the macro to get the state information.
No, you do the same thing for trace_mhi_process_data_event_ring() and
trace_mhi_gen_tre().