[RFC v4][PATCH part-3 00/14] ASI - Part III (ASI Test Driver and CLI)
From: Alexandre Chartre
Date: Mon May 04 2020 - 11:06:30 EST
This is part III of ASI RFC v4. Please refer to the cover letter of
part I for an overview the ASI RFC.
https://lore.kernel.org/lkml/20200504144939.11318-1-alexandre.chartre@xxxxxxxxxx/
This part provides a driver and a CLI for testing and introspecting an
ASI. The driver creates a test ASI and provide the ability to run some
test sequences on the test ASI such as:
- a simple enter/exit ASI
- using printk with ASI
- access a map or unmapped buffer while in ASI
- receive an interrupt or NMI while in ASI
- scheduling in/out a task using ASI
The driver reports if the ASI remains active or not at the end of the
test sequence. It also provides the ability to:
- query the ASI fault (i.e. places where the ASI had a fault)
- clear the ASI fault log
- toggle the reporting of stack trace on an ASI fault
- query ASI mappings (i.e. VA ranges mapped in the ASI)
- add an ASI mapping
- clear an ASI mapping
The asicmd user CLI is provided to interact with the ASI test driver.
More details and examples are provided below for using the asicmd CLI.
Thanks,
alex.
=====
ASI Test Driver and CLI Usage
-----------------------------
The ASI test driver is built as a loadable module (asi.ko) in the
drivers/staging/asi/ directory. You can load it with modprobe or insmod.
The ASI test CLI (asicmd) is built in the drivers/staging/asi/ directory.
The ASI test driver should be loaded before using the asicmd CLI.
Usage:
------
Running the asicmd without arguments will show the different commands
available:
# ./asicmd
Usage: asicmd (<cmd>|<test>...)
Commands:
all - run all tests
fault - list ASI faults
fltclr - clear ASI faults
stkon - show stack on ASI fault
stkoff - do not show stack on ASI fault
map - list ASI mappings
mapadd - add ASI mappings
mapclr - clear ASI mapping
Tests:
nop - enter/exit ASI and nothing else
mem - enter ASI and accessed an unmapped buffer
memmap - enter ASI and accessed a mapped buffer
intr - receive an interruption while running with ASI
nmi - receive a NMI while running with ASI
intrnmi - receive a NMI in an interrupt received while running with ASI
sched - call schedule() while running with ASI
printk - call printk() while running with ASI
Running a Test Sequence:
------------------------
Just specify the test sequence to run. For example, to run the "nop"
test sequence, run "asicmd nop":
# ./asicmd nop
Test nop (sequence 0)
- rv = 0 ; result = 0 ; asi active
- expect = asi active
TEST OK
The command reports that the ASI was active at the end of the test
sequence and that this was the expected result. So the test was
successful.
Another example with the "mem" test sequence:
# ./asicmd mem
Test mem (sequence 2)
- rv = 0 ; result = 0 ; asi inactive
- expect = asi inactive
TEST OK
This tests sequence access a buffer which is not mapped in ASI so it
causes ASI to exit. The test effectively reports that the ASI was inactive
at the end of the test sequence, but this is the expected result so the
test is successful.
All test sequences can be run with the "all" command: asicmd all
Managing ASI Faults:
--------------------
The asicmd CLI has commands to manage ASI faults i.e. faults that occurred
while running ASI because ASI is accessing an unmapped address:
- "asicmd fault" reports all ASI faults. It shows the address where the
fault has occurred and the number of time the fault has occurred.
- "asicmd fltclr" clears the ASI fault log.
For example, the "mem" will cause an ASI fault and we can see it with the
"fault" command:
# ./asicmd fltclr
# ./asicmd fault
ASI has no fault
# ./asicmd mem
Test mem (sequence 2)
- rv = 0 ; result = 0 ; asi inactive
- expect = asi inactive
TEST OK
# ./asicmd fault
ADDRESS COUNT SYMBOL
0xffffffffc0515037 1 asidrv_mem_run+0x37/0x7f [asi]
Managing ASI Mappings:
----------------------
The asicmd CLI has commands to manage ASI mappings i.e. address ranges
which are mapped in the ASI page-table:
- "asicmd map" reports all ASI mappings. It shows the address, size and
page-table level of the mappings.
- "asicmd mapadd" adds a mapping to the ASI page-table. The syntax is:
asicmd mapadd [percpu:]<addr>:<size>[:<level>]
. <addr> is the start address of the mapping and <size> is its size.
. <level> is the page-table level of the mapping, either "pte", "pmd",
"pud", "p4d" or "pgd". By default, the level is "pte".
. "percpu" should be prepended when <addr> is the offset of a percpu
buffer
- "asicmd" mapclr" clears a mapping in the ASI page-table. The syntax is:
asicmd mapclr [percpu:]<addr>
. <addr> is the start address of the mapping. The system automatically
figures out the size and page-table level of the mapping.
. "percpu" should be prepended when <addr> is the offset of a percpu
buffer
Example:
# ./asicmd map
ADDRESS SIZE LEVEL
0xffff88806946f000 0x838 PTE
0xffff88806820a000 0x60 PTE
0xffffffffc0515000 0x7000 PTE
0xffff88807ddac4c0 0xa0 PTE
0xffff88807dd2c4c0 0xa0 PTE
0xffff88807dcac4c0 0xa0 PTE
0xffff88807dc2c4c0 0xa0 PTE
0xffff88807dd98bc0 0x8 PTE
0xffff88807dd18bc0 0x8 PTE
0xffff88807dc98bc0 0x8 PTE
0xffff88807dc18bc0 0x8 PTE
0xffff88807dd80000 0x30 PTE
0xffff88807dd00000 0x30 PTE
0xffff88807dc80000 0x30 PTE
0xffff88807dc00000 0x30 PTE
0xfffffe0000001000 0x8000000000 P4D
0xffffffff80000000 0x40000000 PTE
This shows the default core mappings for ASI. These mappings shouldn't be
removed.
If the ASI faults then you can add the missing mapping. For example with
the "printk" test sequence:
# ./asicmd fltclr
# ./asicmd printk
Test printk (sequence 1)
- rv = 0 ; result = 0 ; asi inactive
- expect = asi active
TEST FAILED - unexpected ASI state
The "printk" test sequence failed because of an ASI fault:
# ./asicmd fault
ADDRESS COUNT SYMBOL
0xffffffff8110b5a1 1 vprintk_func+0x11/0xbc
With the source code or debugger, we can figure out that the fault is due
to printk_context not being mapped in the ASI.
0xffffffff8110b5a1 <+17>: mov %gs:0x7ef106f8(%rip),%eax # 0x1bca0 <printk_context>
So we can add the missing mapping into the ASI with "mapadd"; note that
printk_context is a percpu buffer and that sizeof(printk_context) is 4:
# ./asicmd mapadd percpu:0x1bca0:4
mapadd 1bca0/4/0 percpu
If we re-run the "printk" test then we got:
# ./asicmd fltclr
# ./asicmd printk
Test printk (sequence 1)
- rv = 0 ; result = 0 ; asi inactive
- expect = asi active
TEST FAILED - unexpected ASI state
# ./asicmd fault
ADDRESS COUNT SYMBOL
0xffffffff811081f3 1 log_store.constprop.27+0x1f3/0x280
We still see a new fault but at a difference address (this time because
cpu_number is not mapped).
-----
Alexandre Chartre (14):
mm/asi: Define the test ASI type
asidrv: Introduce the ASI driver
asidrv: Introduce the ASIDRV_IOCTL_RUN_SEQUENCE ioctl
asidrv: Sequence to test ASI access to mapped/unmapped memory
asidrv: Sequence to test interrupt on ASI
asidrv: Sequence to test NMI on ASI
asidrv: Sequence to test interrupt+NMI on ASI
asidrv: Sequence to test scheduling in/out with ASI
asidrv: Add ioctls to manage ASI page faults
asidrv: Add ioctls to manage ASI mapped VA ranges
asidrv/asicmd: Introduce the asicmd command
asidrv/asicmd: Add more test sequences for testing ASI
asidrv/asicmd: Add options to manage ASI page faults
asidrv/asicmd: Add options to manage ASI mapped VA ranges
arch/x86/include/asm/asi.h | 2 +
arch/x86/mm/asi.c | 1 +
drivers/staging/Makefile | 1 +
drivers/staging/asi/Makefile | 13 +
drivers/staging/asi/asicmd.c | 439 ++++++++++++++
drivers/staging/asi/asidrv.c | 1077 ++++++++++++++++++++++++++++++++++
drivers/staging/asi/asidrv.h | 102 ++++
7 files changed, 1635 insertions(+)
create mode 100644 drivers/staging/asi/Makefile
create mode 100644 drivers/staging/asi/asicmd.c
create mode 100644 drivers/staging/asi/asidrv.c
create mode 100644 drivers/staging/asi/asidrv.h
--
2.18.2