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Re: [Qemu-ppc] [PATCH 2/3] pseries: Allow writes to KVM accelerated TCE

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH 2/3] pseries: Allow writes to KVM accelerated TCE table
Date: Sun, 30 Oct 2011 18:07:11 +0100

On 28.10.2011, at 03:56, David Gibson wrote:

> Sufficiently recent kernels include a KVM call to accelerate use of
> PAPR TCE tables (IOMMU), which are used by PAPR virtual IO devices.
> This involves qemu mapping the TCE table in from a kernel obtained fd,
> which currently we do with PROT_READ only.  This is a hangover from
> early (never released) versions of this kernel interface which only
> permitted read-only mappings and required us to destroy and recreate
> the table when we needed to clear it from qemu.
> Now, the kernel permits read-write mappings, and we rely on this to
> clear the table in spapr_vio_quiesce_one().  However, due to
> insufficient testing, I forgot to update the actual mapping of the
> table in kvmppc_create_spapr_tce() to add PROT_WRITE to the mmap().
> This patch corrects the oversight.
> Signed-off-by: David Gibson <address@hidden>

Thanks, applied to ppc-next.


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