linux-kernel - Re: [patch V4 part 1 29/36] x86/mce: Send #MC singal from task work

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Message-ID: <20200514141616.GC9266@zn.tnic>
Date:   Thu, 14 May 2020 16:16:16 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [patch V4 part 1 29/36] x86/mce: Send #MC singal from task work

On Thu, May 07, 2020 at 11:02:09AM -0700, Andy Lutomirski wrote:
> IOW, if we want to recover from CPL0 #MC, we will need a different mechanism.

Recovering from CPL0 #MC is mostly doomed to failure. Except this mcsafe
crap with the exception handling:

                /*
                 * Handle an MCE which has happened in kernel space but from
                 * which the kernel can recover: ex_has_fault_handler() has
                 * already verified that the rIP at which the error happened is
                 * a rIP from which the kernel can recover (by jumping to
                 * recovery code specified in _ASM_EXTABLE_FAULT()) and the
                 * corresponding exception handler which would do that is the
                 * proper one.
                 */
                if (m.kflags & MCE_IN_KERNEL_RECOV) {
                        if (!fixup_exception(regs, X86_TRAP_MC, error_code, 0))
                                mce_panic("Failed kernel mode recovery", &m, msg);


Other than that, we iz done.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette