On Friday 05 November 2010 16:43:33 Michael S. Tsirkin wrote: > On Fri, Nov 05, 2010 at 10:44:19AM +0800, Sheng Yang wrote: > > > > +}; > > > > + > > > > +This ioctl would enable in-kernel MSI-X emulation, which would > > > > handle MSI-X +mask bit in the kernel. > > > > > > What happens on repeated calls when it's already enabled? > > > How does one disable after it's enabled? > > > > Suppose this should only be called once. But again would update the MMIO > > base. > > So maybe add this all to documentation. > > > It > > would be disabled along with device deassignment. > > So what are you going to do when guest enables and later disables MSIX? > Disable assignment completely?
This device goes with PCI resources allocation, rather than IRQ assignment. > > > We enable it explicitly because > > not all devices have MSI-X capability. > > > > > > + > > > > > > This is very specialized for assigned devices. I would like an > > > interface not tied to assigned devices explicitly > > > (even if the implementation at the moment only works > > > for assigned devices, I can patch that in later). E.g. vhost-net would > > > benefit from such an extension too. Maybe tie this to a special > > > GSI and this GSI can be an assigned device or not? > > > > You're talking about KVM_ASSIGN_GET_MSIX_ENTRY? > > Yes but also, and more importantly, about KVM_ASSIGN_REG_MSIX_MMIO > and kvm_assigned_msix_mmio really. > > > We can't tie it to GSI, because we > > should also cover entries without GSI. The entry number should be fine > > for all kinds of devices using MSI-X. > > I don't completely understand: entries without GSI > never need to inject an interrupt. Why do we care > about them? Let's pass such accesses to userspace. > > In any case, I think MSIX GSIs are inexpensive (we never search them > all), so we could create GSIs for all entries if we wanted to. All mask bit accessing controlled by kernel, in order to keep consistent. > > > I am not sure about what PV one would looks like. > > I use kvm_assigned_msix_entry > > just because it can be easily reused. > > Not only PV, emulated devices too. OK let's try to figure out: > > What happens with userspace is, we inject interrupts either through > ioctls or eventfds. Avoiding an exit to userspace on MSIX > access is beneficial in exactly the same way. > > We could have an ioctl to pass in the table addresses, and mapping > table to relevant GSIs. For example, add kvm_msix_mmio with table > start/end, also specify which GSIs are covered. > Maybe ask that userspace allocate all GSIs for a table consequitively? > Or add kvm_irq_routing_msix which is same as msi but > also has the mmio addresses? Bonus points for avoiding the need > to scan all table on each write. For example, don't scan at all, > instead just set a bit in KVM, and set irq entry on the next > interrupt only: we have KVM_MAX_MSIX_PER_DEV as 256 so maybe a small 32 > byte bitmap would be enough for this, avoding a linear scan. > > When we pass in kvm_msix_mmio, kvm would start registering masked state. > > > > > +4.48 KVM_ASSIGN_GET_MSIX_ENTRY > > > > + > > > > +Capability: KVM_CAP_DEVICE_MSIX_MASK > > > > +Architectures: x86 > > > > +Type: vm ioctl > > > > +Parameters: struct kvm_assigned_msix_entry (in and out) > > > > +Returns: 0 on success, !0 on error > > > > + > > > > +struct kvm_assigned_msix_entry { > > > > + /* Assigned device's ID */ > > > > + __u32 assigned_dev_id; > > > > + /* Ignored */ > > > > + __u32 gsi; > > > > + /* The index of entry in the MSI-X table */ > > > > + __u16 entry; > > > > + /* Querying flags and returning status */ > > > > + __u16 flags; > > > > + /* Must be 0 */ > > > > + __u16 padding[2]; > > > > +}; > > > > + > > > > +This ioctl would allow userspace to get the status of one specific > > > > MSI-X +entry. Currently we support mask bit status querying. > > > > + > > > > > > > > 5. The kvm_run structure > > > > > > > > Application code obtains a pointer to the kvm_run structure by > > > > > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > > > index f3f86b2..8fd5121 100644 > > > > --- a/arch/x86/kvm/x86.c > > > > +++ b/arch/x86/kvm/x86.c > > > > @@ -1926,6 +1926,7 @@ int kvm_dev_ioctl_check_extension(long ext) > > > > > > > > case KVM_CAP_DEBUGREGS: > > > > case KVM_CAP_X86_ROBUST_SINGLESTEP: > > > > > > > > case KVM_CAP_XSAVE: > > > > + case KVM_CAP_DEVICE_MSIX_MASK: > > > > r = 1; > > > > break; > > > > > > > > case KVM_CAP_COALESCED_MMIO: > > > > diff --git a/include/linux/kvm.h b/include/linux/kvm.h > > > > index 919ae53..eafafb1 100644 > > > > --- a/include/linux/kvm.h > > > > +++ b/include/linux/kvm.h > > > > @@ -540,6 +540,9 @@ struct kvm_ppc_pvinfo { > > > > > > > > #endif > > > > #define KVM_CAP_PPC_GET_PVINFO 57 > > > > #define KVM_CAP_PPC_IRQ_LEVEL 58 > > > > > > > > +#ifdef __KVM_HAVE_MSIX > > > > +#define KVM_CAP_DEVICE_MSIX_MASK 59 > > > > +#endif > > > > > > We seem to have these HAVE macros all over. > > > Avi, what's the idea? Let's drop them? > > > > Um? This kind of marcos are used here to avoid vendor specific string in > > the header file. > > Am I the only one that dislikes the ifdefs we have all over this code then? > Rest of linux tries to keep ifdefs local by stubbing functionality out. > > > > > + BUG_ON(adev->msix_mmio_base == 0); > > > > > > Below I see > > > > > > adev->msix_mmio_base = msix_mmio->base_addr; > > > > > > which comes from userspace. BUG_ON is an unfriendly way to > > > tell user about a bug in qemu. > > > > > > Anyway, I don't think we should special-case 0 gpa. > > > It's up to the user where to base the table. > > > Use a separate flag to signal that table was initialized. > > > > Base_addr can't be 0 in any case. Only the unimplemented BAR are > > hardwired to zero. > > No, the PCI spec does not say so. Check it out: the unimplemented BAR > is hardwired to zero but implemented can be set to 0 as well. OK, OK, OK, I would add one more flag. > > > Also if we get here with base_addr = 0, it is surely a bug. > > > > > > + > > > > + return -EINVAL; > > > > +} > > > > + > > > > +static int msix_mmio_read(struct kvm_io_device *this, gpa_t addr, > > > > int len, + void *val) > > > > +{ > > > > + struct kvm_assigned_dev_kernel *adev = > > > > + container_of(this, struct > > > > kvm_assigned_dev_kernel, > > > > + msix_mmio_dev); > > > > + int idx, r = 0; > > > > + u32 entry[4]; > > > > + struct kvm_kernel_irq_routing_entry e; > > > > + > > > > + mutex_lock(&adev->kvm->lock); > > > > + if (!msix_mmio_in_range(adev, addr, len)) { > > > > + r = -EOPNOTSUPP; > > > > + goto out; > > > > + } > > > > + if ((addr & 0x3) || len != 4) > > > > + goto out; > > > > + > > > > + idx = msix_get_enabled_idx(adev, addr, len); > > > > + if (idx < 0) { > > > > + idx = (addr - adev->msix_mmio_base) / > > > > PCI_MSIX_ENTRY_SIZE; > > > > + if ((addr % PCI_MSIX_ENTRY_SIZE) == > > > > + PCI_MSIX_ENTRY_VECTOR_CTRL) > > > > + *(unsigned long *)val = > > > > + test_bit(idx, adev->msix_mask_bitmap) ? > > > > + PCI_MSIX_ENTRY_CTRL_MASKBIT : 0; > > > > > > I suspect this is wrong for big endian platforms: PCI returns > > > all values in little endian format. > > > > Let big endian platform take care of it later... There is only x86 has > > __KVM_HAVE_MSIX now. > > Well it's easier to make the code correct when you write it than later. Go back to me if someone want to implement MSI device assignment on big-endian machine. > > > > + else > > > > + r = -EOPNOTSUPP; > > > > + goto out; > > > > + } > > > > + > > > > + r = kvm_get_irq_routing_entry(adev->kvm, > > > > + adev->guest_msix_entries[idx].vector, &e); > > > > + if (r || e.type != KVM_IRQ_ROUTING_MSI) { > > > > + printk(KERN_WARNING "KVM: Wrong MSI-X routing entry! " > > > > + "idx %d, addr 0x%llx, len %d\n", idx, addr, > > > > len); > > > > > > Can a malicious userspace trigger this intentionally? > > > > No. > > Here's a scenario: bind an MSIX routing entry to device, then later > change its type to regular interrupt. Fills the log with warnings, > doesn't it? Does QEmu suppose to discard the old routing? > > > > + r = -EOPNOTSUPP; > > > > + goto out; > > > > + } > > > > + entry[0] = e.msi.address_lo; > > > > + entry[1] = e.msi.address_hi; > > > > + entry[2] = e.msi.data; > > > > + entry[3] = test_bit(adev->guest_msix_entries[idx].entry, > > > > + adev->msix_mask_bitmap); > > > > > > I suspect this is wrong for big endian platforms: PCI returns > > > all values in little endian format. > > > > > > > + memcpy(val, &entry[addr % PCI_MSIX_ENTRY_SIZE / 4 > > > > > > 4 is sizeof *entry? > > > > 4 elements. > > In fact "PCI_MSIX_ENTRY_SIZE / sizeof u32". > > Are you sure? This does not make sense to me. address in bytes, we > take offset from start of entry in bytes, to figure which dword we need > we divide by size of dword. No? I've corrected this one. -- regards Yang, Sheng > > > > ], len); > > > > > > > + > > > > +out: > > > > + mutex_unlock(&adev->kvm->lock); > > > > + return r; > > > > +} > > > > + > > > > +static int msix_mmio_write(struct kvm_io_device *this, gpa_t addr, > > > > int len, + const void *val) > > > > +{ > > > > + struct kvm_assigned_dev_kernel *adev = > > > > + container_of(this, struct > > > > kvm_assigned_dev_kernel, > > > > + msix_mmio_dev); > > > > + int idx, r = 0; > > > > + unsigned long new_val = *(unsigned long *)val; > > > > > > I suspect this is wrong for big endian platforms: PCI returns > > > all values in little endian format. > > > > > > > + > > > > + mutex_lock(&adev->kvm->lock); > > > > + if (!msix_mmio_in_range(adev, addr, len)) { > > > > + r = -EOPNOTSUPP; > > > > + goto out; > > > > + } > > > > + if ((addr & 0x3) || len != 4) > > > > + goto out; > > > > + > > > > + idx = msix_get_enabled_idx(adev, addr, len); > > > > + if (idx < 0) { > > > > + idx = (addr - adev->msix_mmio_base) / > > > > PCI_MSIX_ENTRY_SIZE; > > > > + if (((addr % PCI_MSIX_ENTRY_SIZE) == > > > > + PCI_MSIX_ENTRY_VECTOR_CTRL)) { > > > > + if (new_val & ~PCI_MSIX_ENTRY_CTRL_MASKBIT) > > > > + goto out; > > > > + if (new_val & PCI_MSIX_ENTRY_CTRL_MASKBIT) > > > > + set_bit(idx, adev->msix_mask_bitmap); > > > > + else > > > > + clear_bit(idx, adev->msix_mask_bitmap); > > > > + } else > > > > + /* Userspace would handle other MMIO writing */ > > > > + r = -EOPNOTSUPP; > > > > + goto out; > > > > + } > > > > + if (addr % PCI_MSIX_ENTRY_SIZE != PCI_MSIX_ENTRY_VECTOR_CTRL) { > > > > + r = -EOPNOTSUPP; > > > > + goto out; > > > > + } > > > > + if (new_val & ~PCI_MSIX_ENTRY_CTRL_MASKBIT) > > > > + goto out; > > > > + update_msix_mask(adev, idx, !!(new_val & > > > > PCI_MSIX_ENTRY_CTRL_MASKBIT)); +out: > > > > + mutex_unlock(&adev->kvm->lock); > > > > + > > > > + return r; > > > > +} > > > > + > > > > +static const struct kvm_io_device_ops msix_mmio_ops = { > > > > + .read = msix_mmio_read, > > > > + .write = msix_mmio_write, > > > > +}; > > > > + > > > > +static int kvm_vm_ioctl_register_msix_mmio(struct kvm *kvm, > > > > + struct kvm_assigned_msix_mmio > > > > *msix_mmio) > > > > +{ > > > > + int r = 0; > > > > + struct kvm_assigned_dev_kernel *adev; > > > > + > > > > + mutex_lock(&kvm->lock); > > > > + adev = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head, > > > > + msix_mmio->assigned_dev_id); > > > > + if (!adev) { > > > > + r = -EINVAL; > > > > + goto out; > > > > + } > > > > + if (msix_mmio->base_addr == 0) { > > > > + r = -EINVAL; > > > > + goto out; > > > > + } > > > > + > > > > + mutex_lock(&kvm->slots_lock); > > > > + if (adev->msix_mmio_base == 0) { > > > > > > What does this do? Handles case we are already registered? > > > Also ! adev->msix_mmio_base > > > > We don't need to register again. Just update the address. > > > > Well, msix_mmio_base is an address. I think ==0 is more properly. > > Yes, there's a test above that validates for 0 and returns EINVAL. > But using a separate flag that userspace can not control > to mean 'already registered' will make the code clearer. > > > -- > > regards > > Yang, Sheng > > > > > > + kvm_iodevice_init(&adev->msix_mmio_dev, &msix_mmio_ops); > > > > + r = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, > > > > + &adev->msix_mmio_dev); > > > > + if (r) > > > > + goto out2; > > > > + } > > > > + > > > > + adev->msix_mmio_base = msix_mmio->base_addr; > > > > +out2: > > > > + mutex_unlock(&kvm->slots_lock); > > > > +out: > > > > + mutex_unlock(&kvm->lock); > > > > + > > > > + return r; > > > > +} > > > > > > > > #endif > > > > > > > > long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl, > > > > > > > > @@ -812,6 +1065,36 @@ long kvm_vm_ioctl_assigned_device(struct kvm > > > > *kvm, unsigned ioctl, > > > > > > > > goto out; > > > > > > > > break; > > > > > > > > } > > > > > > > > + case KVM_ASSIGN_GET_MSIX_ENTRY: { > > > > + struct kvm_assigned_msix_entry entry; > > > > + r = -EFAULT; > > > > + if (copy_from_user(&entry, argp, sizeof entry)) > > > > + goto out; > > > > + r = kvm_vm_ioctl_get_msix_entry(kvm, &entry); > > > > + if (r) > > > > + goto out; > > > > + r = -EFAULT; > > > > + if (copy_to_user(argp, &entry, sizeof entry)) > > > > + goto out; > > > > + r = 0; > > > > + break; > > > > + } > > > > + case KVM_ASSIGN_REG_MSIX_MMIO: { > > > > + struct kvm_assigned_msix_mmio msix_mmio; > > > > + > > > > + r = -EFAULT; > > > > + if (copy_from_user(&msix_mmio, argp, sizeof(msix_mmio))) > > > > + goto out; > > > > + > > > > + r = -EINVAL; > > > > + if (msix_mmio.flags != 0 || msix_mmio.reserved != 0) > > > > + goto out; > > > > + > > > > + r = kvm_vm_ioctl_register_msix_mmio(kvm, &msix_mmio); > > > > + if (r) > > > > + goto out; > > > > + break; > > > > + } > > > > > > > > #endif > > > > > > > > } > > > > > > > > out: -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html