On Tue, Oct 21, 2014 at 04:49:43PM -0200, Thadeu Lima de Souza Cascardo wrote: >When IOMMU bypass is enabled, a PCI device can read and write memory >that was not mapped by the driver without causing an EEH. That might >cause memory corruption, for example. > >When we disable bypass, DMA reads and writes to addresses not mapped by >the IOMMU will cause an EEH, allowing us to debug such issues. > >Signed-off-by: Thadeu Lima de Souza Cascardo <casca...@linux.vnet.ibm.com>
Reviewed-by: Gavin Shan <gws...@linux.vnet.ibm.com> Except minor things as below. >--- > Documentation/kernel-parameters.txt | 2 ++ > arch/powerpc/platforms/powernv/pci-ioda.c | 24 +++++++++++++++++++++++- > 2 files changed, 25 insertions(+), 1 deletions(-) > >diff --git a/Documentation/kernel-parameters.txt >b/Documentation/kernel-parameters.txt >index 988160a..b03322a 100644 >--- a/Documentation/kernel-parameters.txt >+++ b/Documentation/kernel-parameters.txt >@@ -1454,6 +1454,8 @@ bytes respectively. Such letter suffixes can also be >entirely omitted. > forcesac > soft > pt [x86, IA-64] >+ nobypass [PPC/POWERNV] >+ Disable IOMMU bypass, using IOMMU for PCI devices. > > > io7= [HW] IO7 for Marvel based alpha systems >diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c >b/arch/powerpc/platforms/powernv/pci-ioda.c >index 468a0f2..58a5a27 100644 >--- a/arch/powerpc/platforms/powernv/pci-ioda.c >+++ b/arch/powerpc/platforms/powernv/pci-ioda.c >@@ -75,6 +75,27 @@ static void pe_level_printk(const struct pnv_ioda_pe *pe, >const char *level, > #define pe_info(pe, fmt, ...) \ > pe_level_printk(pe, KERN_INFO, fmt, ##__VA_ARGS__) > >+static int __read_mostly disable_bypass; >+ static bool pnv_iommu_bypass_disabled __read_mostly; >+static int __init iommu_setup(char *str) >+{ >+ if (!*str) >+ return -EINVAL; I guess it would be "if (!str)" for malformed option. >+ while (*str) { >+ if (!strncmp(str, "nobypass", 8)) { >+ disable_bypass = 1; >+ pr_info("ppc iommu: disabling bypass.\n"); It would be more precise since the option is only visible to PowerNV: pr_info("PowerNV: IOMMU bypass window disabled\n"); >+ } >+ str += strcspn(str, ","); >+ if (*str == ',') >+ str++; >+ } >+ >+ return 0; >+} >+ >+early_param("iommu", iommu_setup); >+ > /* > * stdcix is only supposed to be used in hypervisor real mode as per > * the architecture spec >@@ -1243,7 +1264,8 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb >*phb, > pnv_ioda_setup_bus_dma(pe, pe->pbus, true); > > /* Also create a bypass window */ >- pnv_pci_ioda2_setup_bypass_pe(phb, pe); >+ if (!disable_bypass) >+ pnv_pci_ioda2_setup_bypass_pe(phb, pe); > return; > fail: > if (pe->tce32_seg >= 0) Thanks, Gavin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/