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    Subject[PATCH 5.4 15/15] x86/speculation/mmio: Print SMT warning
    Date
    From: Josh Poimboeuf <jpoimboe@kernel.org>

    commit 1dc6ff02c8bf77d71b9b5d11cbc9df77cfb28626 upstream

    Similar to MDS and TAA, print a warning if SMT is enabled for the MMIO
    Stale Data vulnerability.

    Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kernel/cpu/bugs.c | 11 +++++++++++
    1 file changed, 11 insertions(+)

    --- a/arch/x86/kernel/cpu/bugs.c
    +++ b/arch/x86/kernel/cpu/bugs.c
    @@ -1215,6 +1215,7 @@ static void update_mds_branch_idle(void)

    #define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
    #define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
    +#define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"

    void cpu_bugs_smt_update(void)
    {
    @@ -1259,6 +1260,16 @@ void cpu_bugs_smt_update(void)
    break;
    }

    + switch (mmio_mitigation) {
    + case MMIO_MITIGATION_VERW:
    + case MMIO_MITIGATION_UCODE_NEEDED:
    + if (sched_smt_active())
    + pr_warn_once(MMIO_MSG_SMT);
    + break;
    + case MMIO_MITIGATION_OFF:
    + break;
    + }
    +
    mutex_unlock(&spec_ctrl_mutex);
    }


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