linux-kernel - Re: [PATCH v2 03/35] x86/bugs: Add AUTO mitigations for mds/taa/mmio/rfds

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Message-ID: <20241114022654.qr35ebyspjh4zayj@desk>
Date: Wed, 13 Nov 2024 18:26:54 -0800
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: David Kaplan <david.kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/35] x86/bugs: Add AUTO mitigations for
 mds/taa/mmio/rfds

On Tue, Nov 05, 2024 at 03:54:23PM -0600, David Kaplan wrote:
> @@ -1995,6 +2004,7 @@ void cpu_bugs_smt_update(void)
>  		update_mds_branch_idle();
>  		break;
>  	case MDS_MITIGATION_OFF:
> +	case MDS_MITIGATION_AUTO:

This implies AUTO and OFF are similar, which is counter intuitive.
While mitigation selection code ...

> +	if (mds_mitigation == MDS_MITIGATION_AUTO)
> +		mds_mitigation = MDS_MITIGATION_FULL;
> +

... indicates that AUTO is equivalent to FULL. So, I think AUTO should be
handled the same way as FULL in cpu_bugs_smt_update() as well.

Same for TAA and MMIO below.

>  		break;
>  	}
>  
> @@ -2006,6 +2016,7 @@ void cpu_bugs_smt_update(void) break;
>  	case TAA_MITIGATION_TSX_DISABLED:
>  	case TAA_MITIGATION_OFF:
> +	case TAA_MITIGATION_AUTO:
>  		break;
>  	}
>  
> @@ -2016,6 +2027,7 @@ void cpu_bugs_smt_update(void)
>  			pr_warn_once(MMIO_MSG_SMT);
>  		break;
>  	case MMIO_MITIGATION_OFF:
> +	case MMIO_MITIGATION_AUTO:
>  		break;
>  	}