powerpc/powernv: Add iommu DMA bypass support for IODA2
This patch adds the support for to create a direct iommu "bypass"
window on IODA2 bridges (such as Power8) allowing to bypass iommu
page translation completely for 64-bit DMA capable devices, thus
significantly improving DMA performances.
Additionally, this adds a hook to the struct iommu_table so that
the IOMMU API / VFIO can disable the bypass when external ownership
is requested, since in that case, the device will be used by an
environment such as userspace or a KVM guest which must not be
allowed to bypass translations.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 7d6dcc6..3b2b4fb 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -21,6 +21,7 @@
#include <linux/irq.h>
#include <linux/io.h>
#include <linux/msi.h>
+#include <linux/memblock.h>
#include <asm/sections.h>
#include <asm/io.h>
@@ -460,9 +461,39 @@
return;
pe = &phb->ioda.pe_array[pdn->pe_number];
+ WARN_ON(get_dma_ops(&pdev->dev) != &dma_iommu_ops);
set_iommu_table_base_and_group(&pdev->dev, &pe->tce32_table);
}
+static int pnv_pci_ioda_dma_set_mask(struct pnv_phb *phb,
+ struct pci_dev *pdev, u64 dma_mask)
+{
+ struct pci_dn *pdn = pci_get_pdn(pdev);
+ struct pnv_ioda_pe *pe;
+ uint64_t top;
+ bool bypass = false;
+
+ if (WARN_ON(!pdn || pdn->pe_number == IODA_INVALID_PE))
+ return -ENODEV;;
+
+ pe = &phb->ioda.pe_array[pdn->pe_number];
+ if (pe->tce_bypass_enabled) {
+ top = pe->tce_bypass_base + memblock_end_of_DRAM() - 1;
+ bypass = (dma_mask >= top);
+ }
+
+ if (bypass) {
+ dev_info(&pdev->dev, "Using 64-bit DMA iommu bypass\n");
+ set_dma_ops(&pdev->dev, &dma_direct_ops);
+ set_dma_offset(&pdev->dev, pe->tce_bypass_base);
+ } else {
+ dev_info(&pdev->dev, "Using 32-bit DMA via iommu\n");
+ set_dma_ops(&pdev->dev, &dma_iommu_ops);
+ set_iommu_table_base(&pdev->dev, &pe->tce32_table);
+ }
+ return 0;
+}
+
static void pnv_ioda_setup_bus_dma(struct pnv_ioda_pe *pe, struct pci_bus *bus)
{
struct pci_dev *dev;
@@ -657,6 +688,56 @@
__free_pages(tce_mem, get_order(TCE32_TABLE_SIZE * segs));
}
+static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable)
+{
+ struct pnv_ioda_pe *pe = container_of(tbl, struct pnv_ioda_pe,
+ tce32_table);
+ uint16_t window_id = (pe->pe_number << 1 ) + 1;
+ int64_t rc;
+
+ pe_info(pe, "%sabling 64-bit DMA bypass\n", enable ? "En" : "Dis");
+ if (enable) {
+ phys_addr_t top = memblock_end_of_DRAM();
+
+ top = roundup_pow_of_two(top);
+ rc = opal_pci_map_pe_dma_window_real(pe->phb->opal_id,
+ pe->pe_number,
+ window_id,
+ pe->tce_bypass_base,
+ top);
+ } else {
+ rc = opal_pci_map_pe_dma_window_real(pe->phb->opal_id,
+ pe->pe_number,
+ window_id,
+ pe->tce_bypass_base,
+ 0);
+
+ /*
+ * We might want to reset the DMA ops of all devices on
+ * this PE. However in theory, that shouldn't be necessary
+ * as this is used for VFIO/KVM pass-through and the device
+ * hasn't yet been returned to its kernel driver
+ */
+ }
+ if (rc)
+ pe_err(pe, "OPAL error %lld configuring bypass window\n", rc);
+ else
+ pe->tce_bypass_enabled = enable;
+}
+
+static void pnv_pci_ioda2_setup_bypass_pe(struct pnv_phb *phb,
+ struct pnv_ioda_pe *pe)
+{
+ /* TVE #1 is selected by PCI address bit 59 */
+ pe->tce_bypass_base = 1ull << 59;
+
+ /* Install set_bypass callback for VFIO */
+ pe->tce32_table.set_bypass = pnv_pci_ioda2_set_bypass;
+
+ /* Enable bypass by default */
+ pnv_pci_ioda2_set_bypass(&pe->tce32_table, true);
+}
+
static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
struct pnv_ioda_pe *pe)
{
@@ -727,6 +808,8 @@
else
pnv_ioda_setup_bus_dma(pe, pe->pbus);
+ /* Also create a bypass window */
+ pnv_pci_ioda2_setup_bypass_pe(phb, pe);
return;
fail:
if (pe->tce32_seg >= 0)
@@ -1286,6 +1369,7 @@
/* Setup TCEs */
phb->dma_dev_setup = pnv_pci_ioda_dma_dev_setup;
+ phb->dma_set_mask = pnv_pci_ioda_dma_set_mask;
/* Setup shutdown function for kexec */
phb->shutdown = pnv_pci_ioda_shutdown;