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SubjectRe: [PATCH v5] x86/mce: Check for writes ignored in MCA_STATUS register
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Hi Boris,

On 6/22/2022 10:29 AM, Borislav Petkov wrote:
> On Fri, Jun 10, 2022 at 07:25:15PM +0000, Smita Koralahalli wrote:
>> arch/x86/kernel/cpu/mce/inject.c | 50 +++++++++++++++++++++++++++++-
>> arch/x86/kernel/cpu/mce/internal.h | 2 +-
>> 2 files changed, 50 insertions(+), 2 deletions(-)
> I've simplified, improved and removed some stuff. See if that still
> works on that platform which ignores writes.

I tested out the patch. Its not behaving as expected. The module fails
silently
again.
> + cpu = get_cpu();
> +
> + for (bank = 0; bank < MAX_NR_BANKS; ++bank) {
> + u64 status = MCI_STATUS_VAL, ipid;
> +
> + /* Check whether bank is populated */
> + rdmsrl(MSR_AMD64_SMCA_MCx_IPID(bank), ipid);
> + if (!ipid)
> + continue;
> +
> + toggle_hw_mce_inject(cpu, true);
> +
> + if (wrmsrl_safe(mca_msr_reg(bank, MCA_STATUS), status)) {

The wrmsrl_safe() doesn't throw an error here.
I think we need to read back the written value and check for it whatsoever.
What do you think?

Thanks,
Smita
> + hw_injection_possible = false;
> + pr_warn("Platform does not allow *hardware* error injection."
> + "Try using APEI EINJ instead.\n");
> + }
> +
> + toggle_hw_mce_inject(cpu, false);
> +
> + break;
> + }
> +
> + put_cpu();
> +}

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