linux-kernel - Re: [PATCH v2 7/7] mm: secretmem: add ability to reserve memory at boot

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Message-ID: <20200727171102.GA3655207@kernel.org>
Date:   Mon, 27 Jul 2020 20:11:02 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Idan Yaniv <idan.yaniv@....com>,
        Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org
Subject: Re: [PATCH v2 7/7] mm: secretmem: add ability to reserve memory at
 boot

Oops, something went wrong with the rebase, this should have been
squashed into the previous patch...

On Mon, Jul 27, 2020 at 07:29:35PM +0300, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> Taking pages out from the direct map and bringing them back may create
> undesired fragmentation and usage of the smaller pages in the direct
> mapping of the physical memory.
> 
> This can be avoided if a significantly large area of the physical memory
> would be reserved for secretmem purposes at boot time.
> 
> Add ability to reserve physical memory for secretmem at boot time using
> "secretmem" kernel parameter and then use that reserved memory as a global
> pool for secret memory needs.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index fb95fad81c79..6f3c2f28160f 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4548,6 +4548,10 @@
>  			Format: integer between 0 and 10
>  			Default is 0.
>  
> +	secretmem=n[KMG]
> +			[KNL,BOOT] Reserve specified amount of memory to
> +			back mappings of secret memory.
> +
>  	skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
>  			xtime_lock contention on larger systems, and/or RCU lock
>  			contention on all systems with CONFIG_MAXSMP set.
> -- 
> 2.26.2
> 

-- 
Sincerely yours,
Mike.