lkml.org 
[lkml]   [2022]   [Jul]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH] x86/bugs: Switch to "auto" when "ibrs" selected on Enhanced IBRS parts
    Currently spectre_v2=ibrs forces write to MSR_IA32_SPEC_CTRL at every
    entry and exit. On Enhanced IBRS parts setting MSR_IA32_SPEC_CTRL[IBRS]
    only once at bootup is sufficient. MSR write at every kernel entry/exit
    incur unnecessary penalty that can be avoided.

    When Enhanced IBRS feature is present, switch from "ibrs" to "auto" mode
    so that appropriate mitigation is selected.

    Fixes: 7c693f54c873 ("x86/speculation: Add spectre_v2=ibrs option to support Kernel IBRS")
    Cc: stable@vger.kernel.org # 5.10+
    Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
    ---
    arch/x86/kernel/cpu/bugs.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
    index 0dd04713434b..7d7ebfdfbeda 100644
    --- a/arch/x86/kernel/cpu/bugs.c
    +++ b/arch/x86/kernel/cpu/bugs.c
    @@ -1303,6 +1303,12 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
    return SPECTRE_V2_CMD_AUTO;
    }

    + if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
    + pr_err("%s selected but CPU supports Enhanced IBRS. Switching to AUTO select\n",
    + mitigation_options[i].option);
    + return SPECTRE_V2_CMD_AUTO;
    + }
    +
    spec_v2_print_cond(mitigation_options[i].option,
    mitigation_options[i].secure);
    return cmd;
    base-commit: 72a8e05d4f66b5af7854df4490e3135168694b6b
    --
    2.35.3


    \
     
     \ /
      Last update: 2022-07-14 07:33    [W:2.683 / U:0.772 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site