From: Mauricio Faria de Oliveira mauricfo@linux.vnet.ibm.com
The H_CPU_BEHAV_* flags should be checked for in the 'behaviour' field of 'struct h_cpu_char_result' -- 'character' is for H_CPU_CHAR_* flags.
Found by playing around with QEMU's implementation of the hypercall:
H_CPU_CHAR=0xf000000000000000 H_CPU_BEHAV=0x0000000000000000
This clears H_CPU_BEHAV_FAVOUR_SECURITY and H_CPU_BEHAV_L1D_FLUSH_PR so pseries_setup_rfi_flush() disables 'rfi_flush'; and it also clears H_CPU_CHAR_L1D_THREAD_PRIV flag. So there is no RFI flush mitigation at all for cpu_show_meltdown() to report; but currently it does:
Original kernel:
# cat /sys/devices/system/cpu/vulnerabilities/meltdown Mitigation: RFI Flush
Patched kernel:
# cat /sys/devices/system/cpu/vulnerabilities/meltdown Not affected
H_CPU_CHAR=0x0000000000000000 H_CPU_BEHAV=0xf000000000000000
This sets H_CPU_BEHAV_BNDS_CHK_SPEC_BAR so cpu_show_spectre_v1() should report vulnerable; but currently it doesn't:
Original kernel:
# cat /sys/devices/system/cpu/vulnerabilities/spectre_v1 Not affected
Patched kernel:
# cat /sys/devices/system/cpu/vulnerabilities/spectre_v1 Vulnerable
Brown-paper-bag-by: Michael Ellerman mpe@ellerman.id.au Fixes: f636c14790ea ("powerpc/pseries: Set or clear security feature flags") Signed-off-by: Mauricio Faria de Oliveira mauricfo@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au (cherry picked from commit 0f9bdfe3c77091e8704d2e510eb7c2c2c6cde524) --- arch/powerpc/platforms/pseries/setup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index ba0a36c577ca..3cb12d27f168 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -484,13 +484,13 @@ static void init_cpu_char_feature_flags(struct h_cpu_char_result *result) * The features below are enabled by default, so we instead look to see * if firmware has *disabled* them, and clear them if so. */ - if (!(result->character & H_CPU_BEHAV_FAVOUR_SECURITY)) + if (!(result->behaviour & H_CPU_BEHAV_FAVOUR_SECURITY)) security_ftr_clear(SEC_FTR_FAVOUR_SECURITY);
- if (!(result->character & H_CPU_BEHAV_L1D_FLUSH_PR)) + if (!(result->behaviour & H_CPU_BEHAV_L1D_FLUSH_PR)) security_ftr_clear(SEC_FTR_L1D_FLUSH_PR);
- if (!(result->character & H_CPU_BEHAV_BNDS_CHK_SPEC_BAR)) + if (!(result->behaviour & H_CPU_BEHAV_BNDS_CHK_SPEC_BAR)) security_ftr_clear(SEC_FTR_BNDS_CHK_SPEC_BAR); }