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    Subject[PATCH 5.4 01/17] selftests/powerpc: rfi_flush: disable entry flush if present
    Date
    From: Russell Currey <ruscur@russell.cc>

    commit fcb48454c23c5679d1a2e252f127642e91b05cbe upstream.

    We are about to add an entry flush. The rfi (exit) flush test measures
    the number of L1D flushes over a syscall with the RFI flush enabled and
    disabled. But if the entry flush is also enabled, the effect of enabling
    and disabling the RFI flush is masked.

    If there is a debugfs entry for the entry flush, disable it during the RFI
    flush and restore it later.

    Reported-by: Spoorthy S <spoorts2@in.ibm.com>
    Signed-off-by: Russell Currey <ruscur@russell.cc>
    Signed-off-by: Daniel Axtens <dja@axtens.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    tools/testing/selftests/powerpc/security/rfi_flush.c | 35 +++++++++++++++----
    1 file changed, 29 insertions(+), 6 deletions(-)

    --- a/tools/testing/selftests/powerpc/security/rfi_flush.c
    +++ b/tools/testing/selftests/powerpc/security/rfi_flush.c
    @@ -50,16 +50,30 @@ int rfi_flush_test(void)
    __u64 l1d_misses_total = 0;
    unsigned long iterations = 100000, zero_size = 24 * 1024;
    unsigned long l1d_misses_expected;
    - int rfi_flush_org, rfi_flush;
    + int rfi_flush_orig, rfi_flush;
    + int have_entry_flush, entry_flush_orig;

    SKIP_IF(geteuid() != 0);

    - if (read_debugfs_file("powerpc/rfi_flush", &rfi_flush_org)) {
    + if (read_debugfs_file("powerpc/rfi_flush", &rfi_flush_orig) < 0) {
    perror("Unable to read powerpc/rfi_flush debugfs file");
    SKIP_IF(1);
    }

    - rfi_flush = rfi_flush_org;
    + if (read_debugfs_file("powerpc/entry_flush", &entry_flush_orig) < 0) {
    + have_entry_flush = 0;
    + } else {
    + have_entry_flush = 1;
    +
    + if (entry_flush_orig != 0) {
    + if (write_debugfs_file("powerpc/entry_flush", 0) < 0) {
    + perror("error writing to powerpc/entry_flush debugfs file");
    + return 1;
    + }
    + }
    + }
    +
    + rfi_flush = rfi_flush_orig;

    fd = perf_event_open_counter(PERF_TYPE_RAW, /* L1d miss */ 0x400f0, -1);
    FAIL_IF(fd < 0);
    @@ -68,6 +82,7 @@ int rfi_flush_test(void)

    FAIL_IF(perf_event_enable(fd));

    + // disable L1 prefetching
    set_dscr(1);

    iter = repetitions;
    @@ -109,8 +124,8 @@ again:
    repetitions * l1d_misses_expected / 2,
    passes, repetitions);

    - if (rfi_flush == rfi_flush_org) {
    - rfi_flush = !rfi_flush_org;
    + if (rfi_flush == rfi_flush_orig) {
    + rfi_flush = !rfi_flush_orig;
    if (write_debugfs_file("powerpc/rfi_flush", rfi_flush) < 0) {
    perror("error writing to powerpc/rfi_flush debugfs file");
    return 1;
    @@ -126,11 +141,19 @@ again:

    set_dscr(0);

    - if (write_debugfs_file("powerpc/rfi_flush", rfi_flush_org) < 0) {
    + if (write_debugfs_file("powerpc/rfi_flush", rfi_flush_orig) < 0) {
    perror("unable to restore original value of powerpc/rfi_flush debugfs file");
    return 1;
    }

    + if (have_entry_flush) {
    + if (write_debugfs_file("powerpc/entry_flush", entry_flush_orig) < 0) {
    + perror("unable to restore original value of powerpc/entry_flush "
    + "debugfs file");
    + return 1;
    + }
    + }
    +
    return rc;
    }


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