Re: [PATCH 0/3] powerpc/mce: Fix mce handler and add selftest

[Ganesh]

On 9/17/20 5:59 PM, Michal Suchánek wrote:
Hello,
On Wed, Sep 16, 2020 at 10:52:25PM +0530, Ganesh Goudar wrote:
This patch series fixes mce handling for pseries, provides debugfs
interface for mce injection and adds selftest to test mce handling
on pseries/powernv machines running in hash mmu mode.
debugfs interface and sleftest are added only for slb multihit
injection, We can add other tests in future if possible.

Ganesh Goudar (3):
   powerpc/mce: remove nmi_enter/exit from real mode handler
   powerpc/mce: Add debugfs interface to inject MCE
   selftest/powerpc: Add slb multihit selftest
Is the below logic sound? It does not agree with what is added here:

void machine_check_exception(struct pt_regs *regs)
{
        int recover = 0;

        /*
         * BOOK3S_64 does not call this handler as a non-maskable interrupt
         * (it uses its own early real-mode handler to handle the MCE proper
         * and then raises irq_work to call this handler when interrupts are
         * enabled).
         *
         * This is silly. The BOOK3S_64 should just call a different function
         * rather than expecting semantics to magically change. Something
         * like 'non_nmi_machine_check_exception()', perhaps?
         */
        const bool nmi = !IS_ENABLED(CONFIG_PPC_BOOK3S_64);

        if (nmi) nmi_enter();

Thanks

Michal
Looks like Nick Piggin has the Justification for it, Ill leave Nick to 
answer this.