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In-Reply-To: <a5226797-87b7-ee00-e81d-793b7dc92a80@oracle.com>
References: <cover.1496701658.git.luto@kernel.org> <1de32b6e3ff026886713adab887a9454548d8374.1496701658.git.luto@kernel.org>
 <a5226797-87b7-ee00-e81d-793b7dc92a80@oracle.com>
From: Andy Lutomirski <luto@kernel.org>
Date: Tue, 6 Jun 2017 14:35:46 -0700
Message-ID: <CALCETrVYnoE5orTr9DpcXxKWYhWAVhkL3sP3_Rdd-8L0-H0tjg@mail.gmail.com>
Subject: Re: [RFC 10/11] x86/mm: Enable CR4.PCIDE on supported systems
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Sender: owner-linux-mm@kvack.org
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To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>, Borislav Petkov <bpetkov@suse.de>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mgorman@suse.de>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Nadav Amit <nadav.amit@gmail.com>, Rik van Riel <riel@redhat.com>, Juergen Gross <jgross@suse.com>

On Tue, Jun 6, 2017 at 2:31 PM, Boris Ostrovsky
<boris.ostrovsky@oracle.com> wrote:
>
>> --- a/arch/x86/xen/setup.c
>> +++ b/arch/x86/xen/setup.c
>> @@ -1037,6 +1037,12 @@ void __init xen_arch_setup(void)
>>       }
>>  #endif
>>
>> +     /*
>> +      * Xen would need some work to support PCID: CR3 handling as well
>> +      * as xen_flush_tlb_others() would need updating.
>> +      */
>> +     setup_clear_cpu_cap(X86_FEATURE_PCID);
>
>
> Capabilities for PV guests are typically set in xen_init_capabilities() now.

Do I need this just for PV or for all Xen guests?  Do the
hardware-assisted guests still use paravirt flushes?  Does the
hypervisor either support PCID or correctly clear the PCID CPUID bit?

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