Author: kib Date: Wed Oct 19 18:15:44 2016 New Revision: 307649 URL: https://svnweb.freebsd.org/changeset/base/307649
Log: Partial workaround for Intel PCI adapters reading past the end of the host-programmed DMA regions. This change seemingly fixes the descriptor fetches, but the packet memory accesses are left problematic. Reviewed by: emaste, erj, sbruno Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D8282 Modified: head/sys/dev/e1000/if_lem.c Modified: head/sys/dev/e1000/if_lem.c ============================================================================== --- head/sys/dev/e1000/if_lem.c Wed Oct 19 17:42:45 2016 (r307648) +++ head/sys/dev/e1000/if_lem.c Wed Oct 19 18:15:44 2016 (r307649) @@ -543,8 +543,16 @@ lem_attach(device_t dev) */ adapter->hw.mac.report_tx_early = 1; - tsize = roundup2(adapter->num_tx_desc * sizeof(struct e1000_tx_desc), - EM_DBA_ALIGN); + /* + * It seems that the descriptor DMA engine on some PCI cards + * fetches memory past the end of the last descriptor in the + * ring. These reads are problematic when VT-d (DMAR) busdma + * is used. Allocate the scratch space to avoid getting + * faults from DMAR, by requesting scratch memory for one more + * descriptor. + */ + tsize = roundup2((adapter->num_tx_desc + 1) * + sizeof(struct e1000_tx_desc), EM_DBA_ALIGN); /* Allocate Transmit Descriptor ring */ if (lem_dma_malloc(adapter, tsize, &adapter->txdma, BUS_DMA_NOWAIT)) { @@ -555,8 +563,11 @@ lem_attach(device_t dev) adapter->tx_desc_base = (struct e1000_tx_desc *)adapter->txdma.dma_vaddr; - rsize = roundup2(adapter->num_rx_desc * sizeof(struct e1000_rx_desc), - EM_DBA_ALIGN); + /* + * See comment above txdma allocation for rationale behind +1. + */ + rsize = roundup2((adapter->num_rx_desc + 1) * + sizeof(struct e1000_rx_desc), EM_DBA_ALIGN); /* Allocate Receive Descriptor ring */ if (lem_dma_malloc(adapter, rsize, &adapter->rxdma, BUS_DMA_NOWAIT)) { _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
