diff options
| author | Christoph Hellwig <hch@lst.de> | 2018-04-27 09:13:24 +0200 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2018-05-28 12:48:16 +0200 |
| commit | 06e9552f5f12564dc1c3483f0934d96cc4f72f18 (patch) | |
| tree | 48c92eba3b3c1a7e8576fc84159183481e5e2960 /arch/x86/kernel/pci-dma.c | |
| parent | 84564d1c76255ac6d5fb76c85818cb5961fad061 (diff) | |
x86/pci-dma: remove the experimental forcesac boot option
Limiting the dma mask to avoid PCI (pre-PCIe) DAC cycles while paying
the huge overhead of an IOMMU is rather pointless, and this seriously
gets in the way of dma mapping work.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/pci-dma.c')
| -rw-r--r-- | arch/x86/kernel/pci-dma.c | 21 |
1 files changed, 1 insertions, 20 deletions
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index c7113fd18e32..b65b0d7072f1 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -20,8 +20,6 @@ static int forbid_dac __read_mostly; const struct dma_map_ops *dma_ops = &dma_direct_ops; EXPORT_SYMBOL(dma_ops); -static int iommu_sac_force __read_mostly; - #ifdef CONFIG_IOMMU_DEBUG int panic_on_overflow __read_mostly = 1; int force_iommu __read_mostly = 1; @@ -122,7 +120,7 @@ static __init int iommu_setup(char *p) if (!strncmp(p, "nomerge", 7)) iommu_merge = 0; if (!strncmp(p, "forcesac", 8)) - iommu_sac_force = 1; + pr_warn("forcesac option ignored.\n"); if (!strncmp(p, "allowdac", 8)) forbid_dac = 0; if (!strncmp(p, "nodac", 5)) @@ -162,23 +160,6 @@ int arch_dma_supported(struct device *dev, u64 mask) } #endif - /* Tell the device to use SAC when IOMMU force is on. This - allows the driver to use cheaper accesses in some cases. - - Problem with this is that if we overflow the IOMMU area and - return DAC as fallback address the device may not handle it - correctly. - - As a special case some controllers have a 39bit address - mode that is as efficient as 32bit (aic79xx). Don't force - SAC for these. Assume all masks <= 40 bits are of this - type. Normally this doesn't make any difference, but gives - more gentle handling of IOMMU overflow. */ - if (iommu_sac_force && (mask >= DMA_BIT_MASK(40))) { - dev_info(dev, "Force SAC with mask %Lx\n", mask); - return 0; - } - return 1; } EXPORT_SYMBOL(arch_dma_supported); |