linux-kernel - Re: [PATCH v3 4/6] x86/gsseg: move local_irq_save/restore() into asm_load_gs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8735bpbhat.ffs@tglx>
Date:   Sat, 15 Oct 2022 10:51:54 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Xin Li <xin3.li@...el.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Cc:     mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, peterz@...radead.org, brgerst@...il.com,
        chang.seok.bae@...el.com
Subject: Re: [PATCH v3 4/6] x86/gsseg: move local_irq_save/restore() into
 asm_load_gs_index()

On Thu, Oct 13 2022 at 13:01, Xin Li wrote:
> From: "H. Peter Anvin (Intel)" <hpa@...or.com>
>
> The need to disable/enable interrupts around asm_load_gs_index() is a
> consequence of the implementation. Prepare for using the LKGS
> instruction, which is locally atomic and therefore doesn't need
> interrupts disabled.

*Shudder*. We want less ASM not more.

>  static inline void native_load_gs_index(unsigned int selector)
>  {
> -	unsigned long flags;
> -
> -	local_irq_save(flags);
>  	asm_load_gs_index(selector);
> -	local_irq_restore(flags);
>  }

static inline void native_load_gs_index(unsigned int selector)
{
	unsigned long flags;

        if (cpu_feature_enabled(LKGS)) {
              native_lkgs(selector);
        } else {
	      local_irq_save(flags);
              asm_load_gs_index(selector);
	      local_irq_restore(flags);
       }
}

For paravirt enabled kernels we want during feature detection:

        if (cpu_feature_enabled(LKGS)))
        	pv_ops.cpu.load_gs_index = native_lkgs;

No?

Thanks,

        tglx