linux-kernel - Re: [PATCH 22/43] x86/mm/kaiser: Prepare assembly for entry/exit CR3 switching

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Date:   Sat, 25 Nov 2017 01:02:29 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ingo Molnar <mingo@...nel.org>
cc:     linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 22/43] x86/mm/kaiser: Prepare assembly for entry/exit
 CR3 switching

On Fri, 24 Nov 2017, Ingo Molnar wrote:
> @@ -1288,6 +1308,8 @@ ENTRY(error_entry)
>  	 * from user mode due to an IRET fault.
>  	 */
>  	SWAPGS
> +	/* We have user CR3.  Change to kernel CR3. */
> +	SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
>  
>  .Lerror_entry_from_usermode_after_swapgs:
>  	/* Put us onto the real thread stack. */
> @@ -1333,6 +1355,7 @@ ENTRY(error_entry)
>  	 * gsbase and proceed.  We'll fix up the exception and land in
>  	 * .Lgs_change's error handler with kernel gsbase.
>  	 */
> +	SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
>  	SWAPGS

This is wrong. SWAPGS needs to come first.

Thanks,

	tglx