Hi,
thanks for contributing powerpc tests to kvm-unit-tests, that's very
welcome!
I've got some remarks / questions on the code, though, see below...
On 10.08.2016 03:59, Suraj Jitindar Singh wrote:
> On Power machines if a guest cedes while a tm transaction is in the
> suspended state then the checkpointed state of the vcpu may be lost and we
> lose the cpu in the host.
>
> Add a file for tm tests "powerpc/tm.c" and add a test to check if the fix
> has been applied to the host kernel. If this fix hasn't been applied then
> the test will never complete and the cpu will be lost. Otherwise the test
> should succeed. Since this has the ability to mess things up in the host
> mark this test as don't run by default.
>
> Based on initial work done by: Cyril Bur <cyril.bur@xxxxxxxxxxx>
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
Maybe add a reference to the CVE number? (I think there was one, wasn't it?)
> ---
> lib/powerpc/asm/hcall.h | 1 +
> powerpc/Makefile.common | 3 +-
> powerpc/tm.c | 176 ++++++++++++++++++++++++++++++++++++++++++++++++
> powerpc/unittests.cfg | 6 ++
> 4 files changed, 185 insertions(+), 1 deletion(-)
> create mode 100644 powerpc/tm.c
>
> diff --git a/lib/powerpc/asm/hcall.h b/lib/powerpc/asm/hcall.h
> index 99bce79..80aa3e3 100644
> --- a/lib/powerpc/asm/hcall.h
> +++ b/lib/powerpc/asm/hcall.h
> @@ -18,6 +18,7 @@
> #define H_SET_SPRG0 0x24
> #define H_SET_DABR 0x28
> #define H_PAGE_INIT 0x2c
> +#define H_CEDE 0xE0
> #define H_PUT_TERM_CHAR 0x58
> #define H_RANDOM 0x300
> #define H_SET_MODE 0x31C
> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
> index 677030a..93e4f66 100644
> --- a/powerpc/Makefile.common
> +++ b/powerpc/Makefile.common
> @@ -8,7 +8,8 @@ tests-common = \
> $(TEST_DIR)/selftest.elf \
> $(TEST_DIR)/spapr_hcall.elf \
> $(TEST_DIR)/rtas.elf \
> - $(TEST_DIR)/emulator.elf
> + $(TEST_DIR)/emulator.elf \
> + $(TEST_DIR)/tm.elf
>
> all: $(TEST_DIR)/boot_rom.bin test_cases
>
> diff --git a/powerpc/tm.c b/powerpc/tm.c
> new file mode 100644
> index 0000000..7f675ff
> --- /dev/null
> +++ b/powerpc/tm.c
> @@ -0,0 +1,176 @@
> +/*
> + * Transactional Memory Unit Tests
> + *
> + * Copyright 2016 Suraj Jitindar Singh, IBM.
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2.
> + */
> +#include <libcflat.h>
> +#include <libfdt/libfdt.h>
> +#include <devicetree.h>
> +#include <util.h>
> +#include <alloc.h>
> +#include <asm/hcall.h>
> +#include <asm/ppc_asm.h>
> +#include <asm/processor.h>
> +#include <asm/handlers.h>
> +#include <asm/smp.h>
> +
> +#define US_TO_CYCLES(us) (us << 9)
That's maybe true for current systems (so it's OK for this specific
test, I think), but the cleaner way would be to get the
timebase-frequency from the device tree instead. So I'd like to suggest
that you either add some code to read this value from the device tree,
or add at least an appropriate comment here.
> +/*
> + * Get decrementer value
> + */
> +static uint64_t get_dec(void)
> +{
> + uint64_t dec = 0;
> +
> + asm volatile ( "mfdec %[dec]" : [dec] "+r" (dec)
Why "+r"? I think "=r" should be enough here?
> + :
> + :
You can also omit the empty lines with ":" above.
> + );
> +
> + return dec;
> +}
> +
> +/*
> + * Sleep for <us> micro-seconds (must be less than 4 seconds)
> + */
> +static void sleep(uint64_t us)
Could you please name that function "usleep" instead? The sleep()
function from the libc is traditionally waiting for seconds, not
microseconds, so that could help to avoid some confusing if you name it
usleep() instead.
> +{
> + uint64_t expire_time, dec, cycles = US_TO_CYCLES(us);
> +
> + if (cycles > 0x7FFFFFFF)
> + cycles = 0x7FFFFFFF;
I'd maybe do an "assert(cycles <= 0x7FFFFFFF)" here instead since
otherwise, the code is not doing what the caller expected.
> + if (cycles > (dec = get_dec())) {
It's always easier to read of you put that on two lines:
dec = get_dec();
if (dec < cycles) {
...
> + expire_time = 0x7FFFFFFF + dec - cycles;
> + while (get_dec() < dec)
> + ;
> + } else {
> + expire_time = dec - cycles;
> + }
> +
> + while (get_dec() > expire_time)
> + ;
> +}
> +
> +static int h_cede(void)
> +{
> + register uint64_t r3 asm("r3") = H_CEDE;
> +
> + asm volatile ( "sc 1" : "+r"(r3)
> + :
> + : "r0", "r4", "r5", "r6", "r7", "r8", "r9",
> + "r10", "r11", "r12", "xer", "ctr", "cc"
> + );
> +
> + return r3;
> +}
> +
> +/*
> + * Enable transactional memory
> + * Returns: 0 - Failure
> + * 1 - Success
> + */
> +static bool enable_tm(void)
> +{
> + uint64_t msr = 0;
> +
> + asm volatile ( "mfmsr %[msr]" : [msr] "+r" (msr)
That should be "=r" instead of "+r".
> + :
> + :
> + );
> +
> + msr |= (((uint64_t) 1) << 32);
> +
> + asm volatile ( "mtmsrd %1\n\t"
> + "mfmsr %0" : "+r" (msr)
> + : "r" (msr)
I think you should either use "=r" instead of "+r", or skip the "r"(msr)
input parameter, since the "+" modifier already declares it as
input+output (in the latter case, you've got to change the %1 to %0,
too, obviously).
> + :
> + );
> +
> + return !!(msr & (((uint64_t) 1) << 32));
> +}
> +
> +/*
> + * Test H_CEDE call while transactional memory transaction is suspended
> + *
> + * WARNING: This tests for a known vulnerability in which the host may go down.
> + * Probably best not to run this if your host going down is going to cause
> + * problems.
> + *
> + * If the test passes then your kernel probably has the necessary patch.
> + * If the test fails then the H_CEDE call was unsuccessful and the
> + * vulnerability wasn't tested.
> + * If the test hits the vulnerability then it will never complete or report and
> + * the qemu process will block indefinately. RCU stalls will be detected on the
s/indefinately/indefinitely/
> + * cpu and any process scheduled on the lost cpu will also block indefinitely.
> + */
> +static void test_h_cede_tm(int argc, char **argv)
> +{
> + bool pass = true;
> + int i;
> +
> + if (argc > 2)
> + report_abort("Unsupported argument: '%s'", argv[2]);
> +
> + handle_exception(0x900, &dec_except_handler, NULL);
> +
> + if (!start_all_cpus(&halt, 0))
> + report_abort("Failed to start secondary cpus");
> +
> + if (!enable_tm())
> + report_abort("Failed to enable tm");
> +
> + /*
> + * Begin a transaction and guarantee we are in the suspend state
> + * before continuing
> + */
> + asm volatile ( "1: tbegin.\n\t"
> + "beq 2f\n\t"
> + "tsuspend.\n\t"
> + "2: tcheck cr0\n\t"
> + "bf 2,1b" :
> + :
> + : "cr0"
> + );
> +
> + for (i = 0; i < 500 && pass; i++) {
> + uint64_t rval = h_cede();
> +
> + if (rval != H_SUCCESS)
> + pass = false;
> + sleep(5000);
> + }
> +
> + report("H_CEDE TM", pass);
> +}
> +
> +struct {
> + const char *name;
> + void (*func)(int argc, char **argv);
> +} hctests[] = {
> + { "h_cede_tm", test_h_cede_tm },
> + { NULL, NULL }
> +};
> +
> +int main(int argc, char **argv)
> +{
> + bool all = false;
> + int i;
> +
> + report_prefix_push("tm");
> +
> + all = (argc == 1 || (argc == 2 && !strcmp(argv[1], "all")));
> +
> + for (i = 0; hctests[i].name != NULL; i++) {
> + if (all || strcmp(argv[1], hctests[i].name) == 0) {
> + report_prefix_push(hctests[i].name);
> + hctests[i].func(argc, argv);
> + report_prefix_pop();
> + }
> + }
> +
> + return report_summary();
> +}
Thomas
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