linux-kernel - Re: [PATCH v11 35/37] x86/syscall: Split IDT syscall setup code into idt_syscall

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Date:   Thu, 28 Sep 2023 20:01:48 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "H. Peter Anvin" <hpa@...or.com>, Xin Li <xin3.li@...el.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-edac@...r.kernel.org, linux-hyperv@...r.kernel.org,
        kvm@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:     mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, luto@...nel.org, pbonzini@...hat.com,
        seanjc@...gle.com, peterz@...radead.org, jgross@...e.com,
        ravi.v.shankar@...el.com, mhiramat@...nel.org,
        andrew.cooper3@...rix.com, jiangshanlai@...il.com,
        nik.borisov@...e.com
Subject: Re: [PATCH v11 35/37] x86/syscall: Split IDT syscall setup code
 into idt_syscall_init()

On Mon, Sep 25 2023 at 09:07, H. Peter Anvin wrote:
> On September 23, 2023 2:42:10 AM PDT, Xin Li <xin3.li@...el.com> wrote:
>>+/* May not be marked __init: used by software suspend */
>>+void syscall_init(void)
>>+{
>>+	/* The default user and kernel segments */
>>+	wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
>>+
>>+	idt_syscall_init();
>>+}
>>+
>> #else	/* CONFIG_X86_64 */
>> 
>> #ifdef CONFIG_STACKPROTECTOR
>
> Am I missing something, or is this patch a noop?

Yes. It's a noop at this point. Later on it gains a

     if (!fred)
        idt_syscall_init();

Sure we could do

     if (!fred) {
     	write_msr(foo...);
        ...
     }

too, but I prefer the separation. No strong opinion though.

Thanks,

        tglx