linux-kernel - Re: [RFC PATCH 10/47] mm: asi: Support for global non-sensitive direct map allocations

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Message-ID: <YjuL80tuvUbAWWKW@casper.infradead.org>
Date:   Wed, 23 Mar 2022 21:06:59 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Junaid Shahid <junaids@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pbonzini@...hat.com, jmattson@...gle.com, pjt@...gle.com,
        oweisse@...gle.com, alexandre.chartre@...cle.com,
        rppt@...ux.ibm.com, dave.hansen@...ux.intel.com,
        peterz@...radead.org, tglx@...utronix.de, luto@...nel.org,
        linux-mm@...ck.org
Subject: Re: [RFC PATCH 10/47] mm: asi: Support for global non-sensitive
 direct map allocations

On Tue, Feb 22, 2022 at 09:21:46PM -0800, Junaid Shahid wrote:
> standard ASI instances. A new page flag is also added so that when
> these pages are freed, they can also be unmapped from the ASI page
> tables.

It's cute how you just throw this in as an aside.  Page flags are
in high demand and just adding them is not to be done lightly.  Is
there any other way of accomplishing what you want?

> @@ -542,6 +545,12 @@ TESTCLEARFLAG(Young, young, PF_ANY)
>  PAGEFLAG(Idle, idle, PF_ANY)
>  #endif
>  
> +#ifdef CONFIG_ADDRESS_SPACE_ISOLATION
> +__PAGEFLAG(GlobalNonSensitive, global_nonsensitive, PF_ANY);

Why is PF_ANY appropriate?