linux-kernel - RE: [RESEND PATCH 2/6] x86/traps: add a system interrupt table for system interrupt dispatch

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Date:   Fri, 11 Nov 2022 14:07:05 -0800
From:   "H. Peter Anvin" <hpa@...or.com>
To:     "Li, Xin3" <xin3.li@...el.com>,
        Peter Zijlstra <peterz@...radead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>
Subject: RE: [RESEND PATCH 2/6] x86/traps: add a system interrupt table for system interrupt dispatch

On November 10, 2022 11:55:22 AM PST, "Li, Xin3" <xin3.li@...el.com> wrote:
>> > Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
>> > Signed-off-by: Xin Li <xin3.li@...el.com>
>> 
>> This is not a valid SOB, it would suggest hpa is the author, but he's not in in
>> From.
>
>HPA wrote the initial dispatch code for FRED, and I worked with him to
>refactor it for KVM/VMX NMI/IRQ dispatch.  So use SOB from both.  No?
>
>> > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index
>> > 178015a820f0..95dd917ef9ad 100644
>> > --- a/arch/x86/kernel/traps.c
>> > +++ b/arch/x86/kernel/traps.c
>> > @@ -1444,6 +1444,61 @@ DEFINE_IDTENTRY_SW(iret_error)  }  #endif
>> >
>> > +#define SYSV(x,y) [(x) - FIRST_SYSTEM_VECTOR] =
>> > +(system_interrupt_handler)y
>> > +
>> > +#pragma GCC diagnostic push
>> > +#pragma GCC diagnostic ignored "-Wcast-function-type"
>> 
>> How does this not break CFI ?
>
>I wasn't aware of it, will check.
>

It doesn't break CFI because the arguments passed is always a strict superset of the ones expected and they are free enough that they are always passed in registers.