On Wed, Aug 10, 2016 at 11:59:37AM +1000, 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>
> ---
> 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>
above four includes aren't used
> +#include <asm/hcall.h>
> +#include <asm/ppc_asm.h>
ppc_asm.h unused
> +#include <asm/processor.h>
> +#include <asm/handlers.h>
> +#include <asm/smp.h>
> +
> +#define US_TO_CYCLES(us) (us << 9)
> +
> +/*
> + * Get decrementer value
> + */
> +static uint64_t get_dec(void)
> +{
> + uint64_t dec = 0;
> +
> + asm volatile ( "mfdec %[dec]" : [dec] "+r" (dec)
> + :
> + :
> + );
> +
> + return dec;
> +}
> +
> +/*
> + * Sleep for <us> micro-seconds (must be less than 4 seconds)
> + */
> +static void sleep(uint64_t us)
> +{
> + uint64_t expire_time, dec, cycles = US_TO_CYCLES(us);
> +
> + if (cycles > 0x7FFFFFFF)
> + cycles = 0x7FFFFFFF;
> +
> + if (cycles > (dec = get_dec())) {
> + expire_time = 0x7FFFFFFF + dec - cycles;
> + while (get_dec() < dec)
> + ;
> + } else {
> + expire_time = dec - cycles;
> + }
> +
> + while (get_dec() > expire_time)
> + ;
> +}
You may want to rename this to udelay (like the kernel's naming and
make them available to all powerpc unit tests by adding them to
processor.c. See (not yet merged) patch [*] where I do that for ARM.
[*] https://github.com/rhdrjones/kvm-unit-tests/commit/40f1d91930b3deebdd81d59438083ebcf2ac49e6
> +
> +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
TRUE/FALSE
> + */
> +static bool enable_tm(void)
> +{
> + uint64_t msr = 0;
> +
> + asm volatile ( "mfmsr %[msr]" : [msr] "+r" (msr)
> + :
> + :
> + );
> +
> + msr |= (((uint64_t) 1) << 32);
> +
> + asm volatile ( "mtmsrd %1\n\t"
> + "mfmsr %0" : "+r" (msr)
> + : "r" (msr)
> + :
> + );
> +
> + 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
> + * 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;
nit: initialization unnecessary
> + int i;
> +
> + report_prefix_push("tm");
> +
> + all = (argc == 1 || (argc == 2 && !strcmp(argv[1], "all")));
nit: outer braces unnecessary (and not preferred)
> +
> + 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();
> +}
> diff --git a/powerpc/unittests.cfg b/powerpc/unittests.cfg
> index 0098cb6..20dbde6 100644
> --- a/powerpc/unittests.cfg
> +++ b/powerpc/unittests.cfg
> @@ -53,3 +53,9 @@ groups = rtas
>
> [emulator]
> file = emulator.elf
> +
> +[h_cede_tm]
> +file = tm.elf
> +smp = 2,threads=2
> +extra_params = -append "h_cede_tm"
> +groups = nodefault,h_cede_tm
> --
> 2.5.5
>
Thanks,
drew
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