From: Paolo Bonzini <pbonzini@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Peter Crosthwaite <peter.crosthwaite@xilinx.com>,
patches@linaro.org, qemu-devel@nongnu.org,
Avi Kivity <avi@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] dma: Define dma_context_memory and use in sysbus-ohci
Date: Fri, 26 Oct 2012 15:09:42 +0200 [thread overview]
Message-ID: <508A8B96.60302@redhat.com> (raw)
In-Reply-To: <20121026035812.GK7222@truffula.fritz.box>
Il 26/10/2012 05:58, David Gibson ha scritto:
>> > static inline int dma_memory_rw_relaxed(DMAContext *dma, dma_addr_t addr,
>> > void *buf, dma_addr_t len,
>> > DMADirection dir)
>> > {
>> > if (!dma_has_iommu(dma)) {
>> > /* Fast-path for no IOMMU */
>> > address_space_rw(dma->as, addr, buf, len, dir ==
>> > DMA_DIRECTION_FROM_DEVICE);
>> > return 0;
>> > } else {
>> > return iommu_dma_memory_rw(dma, addr, buf, len, dir);
>> > }
>> > }
>> >
>> > Dereferencing of dma->as segfaults sd dma==NULL in the cas you described.
> Ok. My inclination would be to special case that in that function,
> setting as to the standard memory as if !dma, but others may have a
> different opinion.
Me too, because I'm seeing the exact same segfault with virtio-scsi. Reproducible with:
x86_64-softmmu/qemu-system-x86_64 -device virtio-scsi-pci -drive if=none,id=cd -device scsi-cd,drive=cd
(you don't even need a medium in the drive, it segfaults as soon as the BIOS probes
the device).
As soon as Avi's iommu patches go in, in fact, dma->as will just be as.
Even if as == NULL were to be outlawed and you'd be forced to write
get_address_space_memory(), taking the pain to create dummy DMAContexts
now is just not worth it.
Paolo
next prev parent reply other threads:[~2012-10-26 13:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-23 17:26 [Qemu-devel] [PATCH] dma: Define dma_context_memory and use in sysbus-ohci Peter Maydell
2012-10-25 10:33 ` Peter Crosthwaite
2012-10-26 0:48 ` David Gibson
2012-10-26 2:53 ` Peter Crosthwaite
2012-10-26 3:58 ` David Gibson
2012-10-26 13:09 ` Paolo Bonzini [this message]
2012-10-26 16:00 ` Peter Maydell
2012-11-13 11:44 ` Peter Maydell
2012-11-13 15:04 ` Paolo Bonzini
2012-11-13 15:21 ` Gerd Hoffmann
2012-11-13 15:26 ` Paolo Bonzini
2012-11-18 16:53 ` Avi Kivity
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