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Date:   Wed, 12 May 2021 15:18:57 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Juergen Gross <jgross@suse.com>
Cc:     Andi Kleen <ak@linux.intel.com>, Borislav Petkov <bp@alien8.de>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        Raj Ashok <ashok.raj@intel.com>,
        Sean Christopherson <seanjc@google.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC v2 01/32] x86/paravirt: Introduce CONFIG_PARAVIRT_XL
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On Mon, May 10, 2021 at 05:56:05PM +0200, Juergen Gross wrote:

> No. We have PARAVIRT_XXL for Xen PV guests, and we have PARAVIRT for
> other hypervisor's guests, supporting basically the TLB flush operations
> and time related operations only. Adding the halt related operations to
> PARAVIRT wouldn't break anything.

Also, I don't think anything modern should actually ever hit any of the
HLT instructions, most everything should end up at an MWAIT.

Still, do we wants to give arch_safe_halt() and halt() the
PVOP_ALT_VCALL0() treatment?