From: Jan Kiszka <[email protected]> PCI 2.3 allows to generically disable IRQ sources at device level. This enables us to share IRQs of such devices between on the host side when passing them to a guest.
Signed-off-by: Jan Kiszka <[email protected]> --- include/linux/kvm_host.h | 1 + virt/kvm/assigned-dev.c | 153 +++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 140 insertions(+), 14 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index df5497f..fcdc849 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -473,6 +473,7 @@ struct kvm_assigned_dev_kernel { unsigned int entries_nr; int host_irq; bool host_irq_disabled; + bool pci_2_3; struct msix_entry *host_msix_entries; int guest_irq; struct kvm_guest_msix_entry *guest_msix_entries; diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c index d3ddfea..411643c 100644 --- a/virt/kvm/assigned-dev.c +++ b/virt/kvm/assigned-dev.c @@ -55,10 +55,96 @@ static int find_index_from_host_irq(struct kvm_assigned_dev_kernel return index; } +/* + * Verify that the device supports Interrupt Disable bit in command register, + * per PCI 2.3, by flipping this bit and reading it back: this bit was readonly + * in PCI 2.2. + */ +static bool pci_2_3_supported(struct pci_dev *pdev) +{ + u16 orig, new; + bool supported = false; + + pci_block_user_cfg_access(pdev); + pci_read_config_word(pdev, PCI_COMMAND, &orig); + pci_write_config_word(pdev, PCI_COMMAND, + orig ^ PCI_COMMAND_INTX_DISABLE); + pci_read_config_word(pdev, PCI_COMMAND, &new); + + /* + * There's no way to protect against + * hardware bugs or detect them reliably, but as long as we know + * what the value should be, let's go ahead and check it. + */ + if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) { + dev_err(&pdev->dev, "Command changed from 0x%x to 0x%x: " + "driver or HW bug?\n", orig, new); + goto out; + } + if (!((new ^ orig) & PCI_COMMAND_INTX_DISABLE)) { + dev_warn(&pdev->dev, "Device does not support " + "disabling interrupts: unable to bind.\n"); + goto out; + } + supported = true; + + /* Now restore the original value. */ + pci_write_config_word(pdev, PCI_COMMAND, orig); + +out: + pci_unblock_user_cfg_access(pdev); + return supported; +} + +static void +pci_2_3_mask_irq(struct pci_dev *dev, int mask, unsigned int *irq_status) +{ + u32 cmd_status_dword; + u16 origcmd, newcmd; + + /* + * We do a single dword read to retrieve both command and status. + * Document assumptions that make this possible. + */ + BUILD_BUG_ON(PCI_COMMAND % 4); + BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS); + + pci_block_user_cfg_access(dev); + + /* + * Read both command and status registers in a single 32-bit operation. + * Note: we could cache the value for command and move the status read + * out of the lock if there was a way to get notified of user changes + * to command register through sysfs. Should be good for shared irqs. + */ + pci_read_config_dword(dev, PCI_COMMAND, &cmd_status_dword); + origcmd = cmd_status_dword; + + if (irq_status) { + /* + * Check interrupt status register to see whether our device triggered + * the interrupt. + */ + *irq_status = (cmd_status_dword >> 16) & PCI_STATUS_INTERRUPT; + if (*irq_status == 0) + goto done; + } + + newcmd = origcmd & ~PCI_COMMAND_INTX_DISABLE; + if (mask) + newcmd |= PCI_COMMAND_INTX_DISABLE; + if (newcmd != origcmd) + pci_write_config_word(dev, PCI_COMMAND, newcmd); + +done: + pci_unblock_user_cfg_access(dev); +} + static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id) { struct kvm_assigned_dev_kernel *assigned_dev = (struct kvm_assigned_dev_kernel *) dev_id; + int ret = IRQ_HANDLED; unsigned long flags; spin_lock_irqsave(&assigned_dev->assigned_dev_lock, flags); @@ -83,19 +169,34 @@ static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id) guest_entries[i].vector, 1); } } else { - kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id, - assigned_dev->guest_irq, 1); - if (assigned_dev->irq_requested_type & KVM_DEV_IRQ_GUEST_INTX) { - disable_irq_nosync(irq); + if (assigned_dev->pci_2_3) { + unsigned int irq_status; + + if (assigned_dev->host_irq_disabled) { + ret = IRQ_NONE; + goto out; + } + + pci_2_3_mask_irq(assigned_dev->dev, 1, + &irq_status); + if (irq_status == 0) { + ret = IRQ_NONE; + goto out; + } + } else + disable_irq_nosync(irq); assigned_dev->host_irq_disabled = true; } + + kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id, + assigned_dev->guest_irq, 1); } out: spin_unlock_irqrestore(&assigned_dev->assigned_dev_lock, flags); - return IRQ_HANDLED; + return ret; } /* Ack the irq line for an assigned device */ @@ -117,7 +218,10 @@ static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian) */ spin_lock_irqsave(&dev->assigned_dev_lock, flags); if (dev->host_irq_disabled) { - enable_irq(dev->host_irq); + if (dev->pci_2_3) + pci_2_3_mask_irq(dev->dev, 0, NULL); + else + enable_irq(dev->host_irq); dev->host_irq_disabled = false; } spin_unlock_irqrestore(&dev->assigned_dev_lock, flags); @@ -166,7 +270,11 @@ static void deassign_host_irq(struct kvm *kvm, pci_disable_msix(assigned_dev->dev); } else { /* Deal with MSI and INTx */ - disable_irq(assigned_dev->host_irq); + if (assigned_dev->pci_2_3) { + pci_2_3_mask_irq(assigned_dev->dev, 1, NULL); + synchronize_irq(assigned_dev->host_irq); + } else + disable_irq(assigned_dev->host_irq); free_irq(assigned_dev->host_irq, (void *)assigned_dev); @@ -214,6 +322,13 @@ static void kvm_free_assigned_device(struct kvm *kvm, pci_reset_function(assigned_dev->dev); + /* + * Unmask the IRQ at PCI level once the reset is done - the next user + * may not expect the IRQ being masked. + */ + if (assigned_dev->pci_2_3) + pci_2_3_mask_irq(assigned_dev->dev, 0, NULL); + pci_release_regions(assigned_dev->dev); pci_disable_device(assigned_dev->dev); pci_dev_put(assigned_dev->dev); @@ -239,15 +354,26 @@ void kvm_free_all_assigned_devices(struct kvm *kvm) static int assigned_device_enable_host_intx(struct kvm *kvm, struct kvm_assigned_dev_kernel *dev) { + unsigned long flags = 0; + dev->host_irq = dev->dev->irq; - /* Even though this is PCI, we don't want to use shared - * interrupts. Sharing host devices with guest-assigned devices - * on the same interrupt line is not a happy situation: there - * are going to be long delays in accepting, acking, etc. + + /* + * We can only share the IRQ line with other host devices if we are + * able to disable the IRQ source at device-level - independently of + * the guest driver. Otherwise host devices may suffer from unbounded + * IRQ latencies when the guest keeps the line asserted. */ + dev->pci_2_3 = pci_2_3_supported(dev->dev); + if (dev->pci_2_3) + flags = IRQF_SHARED; + if (request_irq(dev->host_irq, kvm_assigned_dev_intr, - 0, "kvm_assigned_intx_device", (void *)dev)) + flags, "kvm_assigned_intx_device", (void *)dev)) return -EIO; + + if (dev->pci_2_3) + pci_2_3_mask_irq(dev->dev, 0, NULL); return 0; } @@ -324,7 +450,6 @@ static int assigned_device_enable_guest_msi(struct kvm *kvm, { dev->guest_irq = irq->guest_irq; dev->ack_notifier.gsi = -1; - dev->host_irq_disabled = false; return 0; } #endif @@ -336,7 +461,6 @@ static int assigned_device_enable_guest_msix(struct kvm *kvm, { dev->guest_irq = irq->guest_irq; dev->ack_notifier.gsi = -1; - dev->host_irq_disabled = false; return 0; } #endif @@ -367,6 +491,7 @@ static int assign_host_irq(struct kvm *kvm, default: r = -EINVAL; } + dev->host_irq_disabled = false; if (!r) dev->irq_requested_type |= host_irq_type; -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
