From: David Gibson <david@gibson.dropbear.id.au>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [RFC/PATCH] Add a memory barrier to guest memory access functions
Date: Thu, 17 May 2012 13:35:20 +1000 [thread overview]
Message-ID: <20120517033520.GD22069@truffala.fritz.box> (raw)
In-Reply-To: <4FB46257.3060706@codemonkey.ws>
On Wed, May 16, 2012 at 09:28:39PM -0500, Anthony Liguori wrote:
> On 05/16/2012 07:52 PM, Benjamin Herrenschmidt wrote:
[snip]
> >@@ -2794,6 +2795,9 @@ void *qemu_get_ram_ptr(ram_addr_t addr)
> > {
> > RAMBlock *block;
> >
> >+ /* We ensure ordering for all DMA transactions */
> >+ dma_mb();
> >+
>
> I get being conservative, but I don't think this makes a lot of
> sense. There are cases where the return of this function is cached
> (like the VGA ram area). I think it would make more sense if you
> explicitly put a barrier after write operations.
I tend to agree. I think the barriers should be in
cpu_physical_memory_rw() and the st*_phys() functions.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
next prev parent reply other threads:[~2012-05-17 3:50 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-10 4:48 [Qemu-devel] [PATCH 00/13] IOMMU infrastructure Benjamin Herrenschmidt
2012-05-10 4:48 ` [Qemu-devel] [PATCH 01/13] Better support for dma_addr_t variables Benjamin Herrenschmidt
2012-05-10 4:48 ` [Qemu-devel] [PATCH 02/13] Implement cpu_physical_memory_zero() Benjamin Herrenschmidt
2012-05-15 0:42 ` Anthony Liguori
2012-05-15 1:23 ` David Gibson
2012-05-15 2:03 ` Anthony Liguori
2012-05-10 4:48 ` [Qemu-devel] [PATCH 03/13] iommu: Add universal DMA helper functions Benjamin Herrenschmidt
2012-05-10 4:48 ` [Qemu-devel] [PATCH 04/13] usb-ohci: Use " Benjamin Herrenschmidt
2012-05-10 4:48 ` [Qemu-devel] [PATCH 05/13] iommu: Make sglists and dma_bdrv helpers use new universal DMA helpers Benjamin Herrenschmidt
2012-05-10 4:49 ` [Qemu-devel] [PATCH 06/13] ide/ahci: Use universal DMA helper functions Benjamin Herrenschmidt
2012-05-21 1:51 ` [Qemu-devel] [PATCH 06/13 - UPDATED] " Benjamin Herrenschmidt
2012-05-10 4:49 ` [Qemu-devel] [PATCH 07/13] usb: Convert usb_packet_{map, unmap} to universal DMA helpers Benjamin Herrenschmidt
2012-05-10 4:49 ` [Qemu-devel] [PATCH 08/13] iommu: Introduce IOMMU emulation infrastructure Benjamin Herrenschmidt
2012-05-15 0:49 ` Anthony Liguori
2012-05-15 1:42 ` David Gibson
2012-05-15 2:03 ` Anthony Liguori
2012-05-15 2:32 ` Benjamin Herrenschmidt
2012-05-15 2:50 ` Anthony Liguori
2012-05-15 3:02 ` Benjamin Herrenschmidt
2012-05-15 14:02 ` Anthony Liguori
2012-05-15 21:55 ` Benjamin Herrenschmidt
2012-05-15 22:02 ` Anthony Liguori
2012-05-15 23:08 ` Benjamin Herrenschmidt
2012-05-15 23:58 ` Anthony Liguori
2012-05-16 0:41 ` Benjamin Herrenschmidt
2012-05-16 0:54 ` Anthony Liguori
2012-05-16 1:20 ` Benjamin Herrenschmidt
2012-05-16 19:36 ` Anthony Liguori
2012-05-10 4:49 ` [Qemu-devel] [PATCH 09/13] iommu: Add facility to cancel in-use dma memory maps Benjamin Herrenschmidt
2012-05-10 4:49 ` [Qemu-devel] [PATCH 10/13] pseries: Convert sPAPR TCEs to use generic IOMMU infrastructure Benjamin Herrenschmidt
2012-05-10 4:49 ` [Qemu-devel] [PATCH 11/13] iommu: Allow PCI to use " Benjamin Herrenschmidt
2012-05-10 4:49 ` [Qemu-devel] [PATCH 12/13] pseries: Implement IOMMU and DMA for PAPR PCI devices Benjamin Herrenschmidt
2012-05-10 4:49 ` [Qemu-devel] [PATCH 13/13] iommu: Add a memory barrier to DMA RW function Benjamin Herrenschmidt
2012-05-15 0:52 ` Anthony Liguori
2012-05-15 1:11 ` Benjamin Herrenschmidt
2012-05-15 1:44 ` David Gibson
2012-05-16 4:35 ` Benjamin Herrenschmidt
2012-05-16 5:51 ` David Gibson
2012-05-16 19:39 ` Anthony Liguori
2012-05-16 21:10 ` Benjamin Herrenschmidt
2012-05-16 21:12 ` Benjamin Herrenschmidt
2012-05-17 0:07 ` Benjamin Herrenschmidt
2012-05-17 0:24 ` Benjamin Herrenschmidt
2012-05-17 0:52 ` [Qemu-devel] [RFC/PATCH] Add a memory barrier to guest memory access functions Benjamin Herrenschmidt
2012-05-17 2:28 ` Anthony Liguori
2012-05-17 2:44 ` Benjamin Herrenschmidt
2012-05-17 22:09 ` Anthony Liguori
2012-05-18 1:04 ` David Gibson
2012-05-18 1:16 ` Benjamin Herrenschmidt
2012-05-17 3:35 ` David Gibson [this message]
2012-05-18 6:53 ` [Qemu-devel] [PATCH 13/13] iommu: Add a memory barrier to DMA RW function Paolo Bonzini
2012-05-18 8:18 ` Benjamin Herrenschmidt
2012-05-18 8:57 ` Paolo Bonzini
2012-05-18 22:26 ` Benjamin Herrenschmidt
2012-05-19 7:24 ` Paolo Bonzini
2012-05-20 21:36 ` Benjamin Herrenschmidt
2012-05-21 1:56 ` [Qemu-devel] [PATCH] Add a memory barrier to guest memory access functions Benjamin Herrenschmidt
2012-05-21 8:11 ` Paolo Bonzini
2012-05-21 8:31 ` Michael S. Tsirkin
2012-05-21 8:58 ` Benjamin Herrenschmidt
2012-05-21 9:07 ` Benjamin Herrenschmidt
2012-05-21 9:16 ` Benjamin Herrenschmidt
2012-05-21 9:34 ` Michael S. Tsirkin
2012-05-21 9:53 ` Benjamin Herrenschmidt
2012-05-21 10:31 ` Michael S. Tsirkin
2012-05-21 11:45 ` Benjamin Herrenschmidt
2012-05-21 12:18 ` Michael S. Tsirkin
2012-05-21 15:16 ` Paolo Bonzini
2012-05-21 21:58 ` [Qemu-devel] [PATCH] Add a memory barrier to guest memory access function Benjamin Herrenschmidt
2012-05-21 22:22 ` Michael S. Tsirkin
2012-05-21 22:56 ` Benjamin Herrenschmidt
2012-05-22 5:11 ` Michael S. Tsirkin
2012-05-22 0:00 ` Benjamin Herrenschmidt
2012-05-22 4:19 ` Rusty Russell
2012-05-21 22:18 ` [Qemu-devel] [PATCH] Add a memory barrier to guest memory access functions Anthony Liguori
2012-05-21 22:26 ` Benjamin Herrenschmidt
2012-05-21 22:31 ` Anthony Liguori
2012-05-21 22:44 ` Michael S. Tsirkin
2012-05-21 23:02 ` Benjamin Herrenschmidt
2012-05-22 4:34 ` [Qemu-devel] [PATCH] Add a memory barrier to DMA functions Benjamin Herrenschmidt
2012-05-22 4:51 ` Benjamin Herrenschmidt
2012-05-22 7:17 ` Benjamin Herrenschmidt
2012-05-22 11:14 ` Michael S. Tsirkin
2012-05-22 11:41 ` Benjamin Herrenschmidt
2012-05-22 12:03 ` Michael S. Tsirkin
2012-05-22 21:24 ` Benjamin Herrenschmidt
2012-05-22 21:40 ` Anthony Liguori
2012-05-21 22:37 ` [Qemu-devel] [PATCH] Add a memory barrier to guest memory access functions Michael S. Tsirkin
2012-05-15 0:52 ` [Qemu-devel] [PATCH 00/13] IOMMU infrastructure Anthony Liguori
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