illumos gate

When running stock onnv-tip (from the closed gate), the kernel panics when booting in paravirtualised mode (i86xpv), due to:

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/platform/i86xpv/kernel/drv/amd64/rootnex: undefined symbol 'iommulib_nexdma_unmapobject'
WARNING: mod_load: cannot load module 'rootnex'

panic[cpu0]/thread=fffffffffbc609e0: BAD TRAP: type=e
 (#pf Page fault) rp=fffffffffbcb4ec0 addr=20 occurred in module "genunix" due to a NULL pointer dereference

There was a large IOMMU putback (13050:515b1e9bea30) which introduces the issue. Below is (probably rather rough) patch to potentially address the issue (just about to test this):

diff -r b23a4dab3d50 usr/src/uts/i86pc/io/rootnex.c
--- a/usr/src/uts/i86pc/io/rootnex.c    Wed Aug 18 15:52:48 2010 -0600
+++ b/usr/src/uts/i86pc/io/rootnex.c    Sat Sep 11 17:46:36 2010 +0100
@@ -2208,14 +2208,19 @@
         * Clean up and return an error.
         */

+#if defined(__amd64) && !defined(__xpv)
+
        if (dma->dp_dvma_used) {
                (void) iommulib_nexdma_unmapobject(dip, rdip, handle,
                    &dma->dp_dvma);
                e = DDI_DMA_NOMAPPING;
        } else {
+#endif
                e = rootnex_bind_slowpath(hp, dmareq, dma, attr, &dma->dp_dma,
                    kmflag);
-       }
+#if defined(__amd64) && !defined(__xpv)
+       }
+#endif
        if ((e != DDI_DMA_MAPPED) && (e != DDI_DMA_PARTIAL_MAP)) {
                if (dma->dp_need_to_free_cookie) {
                        kmem_free(dma->dp_cookies, dma->dp_cookie_size);
@@ -2328,9 +2333,11 @@
        rootnex_teardown_copybuf(dma);
        rootnex_teardown_windows(dma);

+#if defined(__amd64) && !defined(__xpv)
        if (IOMMU_USED(rdip))
                (void) iommulib_nexdma_unmapobject(dip, rdip, handle,
                    &dma->dp_dvma);
+#endif

        /*
         * If we had to allocate space to for the worse case sgl (it didn't

There may be other iommu related bugs as it doesn't look like the iommu putback was tested extensively (speculation).