linux-kernel - Re: [PATCH] x86/lam: Disable ADDRESS

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Message-ID: <20240119162104.4ehgnj4ptjrfwyhf@windy>
Date: Fri, 19 Jan 2024 08:21:04 -0800
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: Sohil Mehta <sohil.mehta@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	kirill.shutemov@...ux.intel.com, daniel.sneddon@...ux.intel.com,
	antonio.gomez.iglesias@...ux.intel.com, rick.p.edgecombe@...el.com,
	alexander.shishkin@...el.com
Subject: Re: [PATCH] x86/lam: Disable ADDRESS_MASKING in most cases

On Fri, Jan 19, 2024 at 09:48:14AM -0800, Sohil Mehta wrote:
> 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.

The goal is to compile test it whenever possible. As
SPECULATION_MITIGATIONS are ON by default, it wont get tested for most
configuration.