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From:   Andi Kleen <ak@linux.intel.com>
To:     Juergen Gross <jgross@suse.com>
Cc:     xen-devel@lists.xenproject.org, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Alok Kataria <akataria@vmware.com>
Subject: Re: [PATCH 0/2] Remove 32-bit Xen PV guest support
References: <20190715113739.17694-1-jgross@suse.com>
Date:   Mon, 15 Jul 2019 09:34:00 -0700
In-Reply-To: <20190715113739.17694-1-jgross@suse.com> (Juergen Gross's message
        of "Mon, 15 Jul 2019 13:37:37 +0200")
Message-ID: <87y30zfe9z.fsf@linux.intel.com>
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Juergen Gross <jgross@suse.com> writes:

> The long term plan has been to replace Xen PV guests by PVH. The first
> victim of that plan are now 32-bit PV guests, as those are used only
> rather seldom these days. Xen on x86 requires 64-bit support and with
> Grub2 now supporting PVH officially since version 2.04 there is no
> need to keep 32-bit PV guest support alive in the Linux kernel.
> Additionally Meltdown mitigation is not available in the kernel running
> as 32-bit PV guest, so dropping this mode makes sense from security
> point of view, too.

Normally we have a deprecation period for feature removals like this.
You would make the kernel print a warning for some releases, and when
no user complains you can then remove. If a user complains you can't.

-Andi