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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     Alexander Graf <graf@amazon.com>, X86 ML <x86@kernel.org>
Cc:     Andy Lutomirski <luto@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
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        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
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        Tom Lendacky <thomas.lendacky@amd.com>,
        Wei Liu <wei.liu@kernel.org>,
        Michael Kelley <mikelley@microsoft.com>,
        Jason Chen CJ <jason.cj.chen@intel.com>,
        Zhao Yakui <yakui.zhao@intel.com>,
        "Peter Zijlstra \(Intel\)" <peterz@infradead.org>,
        Avi Kivity <avi@scylladb.com>,
        "Herrenschmidt\, Benjamin" <benh@amazon.com>, robketr@amazon.de,
        amos@scylladb.com, Brian Gerst <brgerst@gmail.com>,
        stable@vger.kernel.org
Subject: Re: [PATCH] x86/irq: Preserve vector in orig_ax for APIC code
In-Reply-To: <fd87a87d-7d8a-9959-6c81-f49003a43c21@amazon.com>
References: <20200826115357.3049-1-graf@amazon.com> <87k0xlv5w5.fsf@nanos.tec.linutronix.de> <fd87a87d-7d8a-9959-6c81-f49003a43c21@amazon.com>
Date:   Wed, 26 Aug 2020 20:30:25 +0200
Message-ID: <87blixuuny.fsf@nanos.tec.linutronix.de>
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On Wed, Aug 26 2020 at 18:33, Alexander Graf wrote:
> On 26.08.20 16:27, Thomas Gleixner wrote:
>> The below nasty hack cures it, but I hate it with a passion. I'll look
>> deeper for a sane variant.
>
> An alternative (that doesn't make the code easier to read, but would fix 
> the issue at hand) would be touse a pushq imm16 with vector | 0x8000 
> instead to always make the value negative, no?

Which makes each entry larger than 8 byte which was frowned upon before.

And it does not solve the issue that we abuse orig_ax which Andy
mentioned.

Thanks,

        tglx