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From: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
To: David Gibson <david@gibson.dropbear.id.au>,
	aik@ozlabs.ru, agraf@suse.de, mdroth@us.ibm.com
Cc: paulus@samba.org, qemu-ppc@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [Qemu-ppc] [RFC] pseries: Enable in-kernel H_LOGICAL_CI_{LOAD, STORE} implementations
Date: Tue, 03 Feb 2015 14:26:44 +0530	[thread overview]
Message-ID: <87pp9rweyb.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <1422943851-25836-1-git-send-email-david@gibson.dropbear.id.au>

David Gibson <david@gibson.dropbear.id.au> writes:

> qemu currently implements the hypercalls H_LOGICAL_CI_LOAD and
> H_LOGICAL_CI_STORE as PAPR extensions.  These are used by the SLOF firmware
> for IO, because performing cache inhibited MMIO accesses with the MMU off
> (real mode) is very awkward on POWER.
>
> This approach breaks when SLOF needs to access IO devices implemented
> within KVM instead of in qemu.  The simplest example would be virtio-blk
> using an iothread, because the iothread / dataplane mechanism relies on
> an in-kernel implementation of the virtio queue notification MMIO.
>
> To fix this, an in-kernel implementation of these hypercalls has been made,
> however, the hypercalls still need to be enabled from qemu.  This performs
> the necessary calls to do so.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Reviewed-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>

  reply	other threads:[~2015-02-03  8:56 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-03  6:10 [Qemu-devel] [RFC] pseries: Enable in-kernel H_LOGICAL_CI_{LOAD, STORE} implementations David Gibson
2015-02-03  8:56 ` Nikunj A Dadhania [this message]
2015-02-03 21:19 ` Paul Mackerras
2015-02-04  1:32   ` David Gibson
2015-02-04 15:19     ` Alexander Graf
2015-02-05  0:48       ` David Gibson
2015-02-05  0:54         ` Alexander Graf
2015-02-05  2:55           ` David Gibson
2015-02-05 10:22             ` Alexander Graf
2015-02-05 11:30               ` David Gibson
2015-02-05 11:55                 ` Alexander Graf
2015-02-06  2:54                   ` David Gibson
2015-02-06  7:56                     ` Alexander Graf
2015-02-09  0:37                       ` David Gibson
2015-02-09  1:41                         ` Alexander Graf

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