Patchwork [22/22] pseries: Allow writes to KVM accelerated TCE table

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Submitter Alexander Graf
Date Oct. 30, 2011, 8:23 p.m.
Message ID <1320006193-15219-23-git-send-email-agraf@suse.de>
Download mbox | patch
Permalink /patch/122686/
State New
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Comments

Alexander Graf - Oct. 30, 2011, 8:23 p.m.
From: David Gibson <david@gibson.dropbear.id.au>

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 <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
 target-ppc/kvm.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

Patch

diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index f3d0861..429349f 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -850,7 +850,7 @@  void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t window_size, int *pfd)
     len = (window_size / SPAPR_VIO_TCE_PAGE_SIZE) * sizeof(VIOsPAPR_RTCE);
     /* FIXME: round this up to page size */
 
-    table = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
+    table = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
     if (table == MAP_FAILED) {
         close(fd);
         return NULL;