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Message-ID: <8936e2c6-93b8-417e-9151-041c5f2e1102@intel.com>
Date: Fri, 19 Jan 2024 09:48:14 -0800
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] x86/lam: Disable ADDRESS_MASKING in most cases
Content-Language: en-US
To: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>, Thomas Gleixner
	<tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
	<bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, <x86@kernel.org>
CC: "H. Peter Anvin" <hpa@zytor.com>, <linux-kernel@vger.kernel.org>,
	<kirill.shutemov@linux.intel.com>, <daniel.sneddon@linux.intel.com>,
	<antonio.gomez.iglesias@linux.intel.com>, <rick.p.edgecombe@intel.com>,
	<alexander.shishkin@intel.com>
References: <919b6370a908bb091779ec2eca7ca5e369d57847.1705631230.git.pawan.kumar.gupta@linux.intel.com>
From: Sohil Mehta <sohil.mehta@intel.com>
In-Reply-To: <919b6370a908bb091779ec2eca7ca5e369d57847.1705631230.git.pawan.kumar.gupta@linux.intel.com>
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Hi Pawan,

On 1/18/2024 6:35 PM, Pawan Gupta wrote:
>  arch/x86/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 1566748f16c4..794517df8068 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2270,6 +2270,7 @@ config RANDOMIZE_MEMORY_PHYSICAL_PADDING
>  config ADDRESS_MASKING
>  	bool "Linear Address Masking support"
>  	depends on X86_64
> +	depends on COMPILE_TEST || !SPECULATION_MITIGATIONS # wait for LASS

I was wondering if the COMPILE_TEST dependency here is a bit redundant.

Having ADDRESS_MASKING depend on just !SPECULATION_MITIGATIONS might be
enough to get the LAM code compile tested through various configurations.

I don't have a strong preference here. Mainly looking to understand the
reasoning. Other than that the patch looks fine to me.

Sohil

>  	help
>  	  Linear Address Masking (LAM) modifies the checking that is applied
>  	  to 64-bit linear addresses, allowing software to use of the