linux-kernel - Re: [PATCH 2/6] s390: implement nospec

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Date:   Wed, 17 Jan 2018 14:58:45 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jon Masters <jcm@...hat.com>,
        Marcus Meissner <meissner@...e.de>,
        Jiri Kosina <jkosina@...e.cz>
Subject: Re: [PATCH 2/6] s390: implement nospec_[load|ptr]

On 17.01.2018 10:48, Martin Schwidefsky wrote:
> Implement nospec_load() and nospec_ptr() for s390 with the new
> gmb() barrier between the boundary condition and the load that
> may not be done speculatively.
> 
> Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
> Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
> ---
>  arch/s390/include/asm/barrier.h | 38 ++++++++++++++++++++++++++++++++++++++
>  arch/s390/kernel/alternative.c  |  7 +++++++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
> index 1043260..b8836a6 100644
> --- a/arch/s390/include/asm/barrier.h
> +++ b/arch/s390/include/asm/barrier.h
> @@ -8,6 +8,8 @@
>  #ifndef __ASM_BARRIER_H
>  #define __ASM_BARRIER_H
>  
> +#include <asm/alternative.h>
> +
>  /*
>   * Force strict CPU ordering.
>   * And yes, this is required on UP too when we're talking
> @@ -23,6 +25,42 @@
>  
>  #define mb() do {  asm volatile(__ASM_BARRIER : : : "memory"); } while (0)
>  
> +static inline void gmb(void)
> +{
> +	asm volatile(
> +		ALTERNATIVE("", ".long 0xb2e8f000", 81)
> +		: : : "memory");
> +}

Just to be sure:

There are now 2 new facilities:

81 and 82.

Is 82 just the virtualization (SIE) support for 81?

-- 

Thanks,

David / dhildenb