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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-01-20 14:01:31 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-01-20 14:01:31 -0300
commitb4b7ff4b08e691656c9d77c758fc355833128ac0 (patch)
tree82fcb00e6b918026dc9f2d1f05ed8eee83874cc0 /Documentation/virtual
parent35acfa0fc609f2a2cd95cef4a6a9c3a5c38f1778 (diff)
Linux-libre 4.4-gnupck-4.4-gnu
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt56
-rw-r--r--Documentation/virtual/kvm/arm/vgic-mapped-irqs.txt187
-rw-r--r--Documentation/virtual/kvm/devices/arm-vgic.txt18
-rw-r--r--Documentation/virtual/kvm/devices/vm.txt2
-rw-r--r--Documentation/virtual/kvm/locking.txt12
-rw-r--r--Documentation/virtual/kvm/ppc-pv.txt2
6 files changed, 260 insertions, 17 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index d9ecceea5..092ee9fba 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -401,10 +401,9 @@ Capability: basic
Architectures: x86, ppc, mips
Type: vcpu ioctl
Parameters: struct kvm_interrupt (in)
-Returns: 0 on success, -1 on error
+Returns: 0 on success, negative on failure.
-Queues a hardware interrupt vector to be injected. This is only
-useful if in-kernel local APIC or equivalent is not used.
+Queues a hardware interrupt vector to be injected.
/* for KVM_INTERRUPT */
struct kvm_interrupt {
@@ -414,7 +413,14 @@ struct kvm_interrupt {
X86:
-Note 'irq' is an interrupt vector, not an interrupt pin or line.
+Returns: 0 on success,
+ -EEXIST if an interrupt is already enqueued
+ -EINVAL the the irq number is invalid
+ -ENXIO if the PIC is in the kernel
+ -EFAULT if the pointer is invalid
+
+Note 'irq' is an interrupt vector, not an interrupt pin or line. This
+ioctl is useful if the in-kernel PIC is not used.
PPC:
@@ -1598,7 +1604,7 @@ provided event instead of triggering an exit.
struct kvm_ioeventfd {
__u64 datamatch;
__u64 addr; /* legal pio/mmio address */
- __u32 len; /* 1, 2, 4, or 8 bytes */
+ __u32 len; /* 0, 1, 2, 4, or 8 bytes */
__s32 fd;
__u32 flags;
__u8 pad[36];
@@ -1621,6 +1627,10 @@ to the registered address is equal to datamatch in struct kvm_ioeventfd.
For virtio-ccw devices, addr contains the subchannel id and datamatch the
virtqueue index.
+With KVM_CAP_IOEVENTFD_ANY_LENGTH, a zero length ioeventfd is allowed, and
+the kernel will ignore the length of guest write and may get a faster vmexit.
+The speedup may only apply to specific architectures, but the ioeventfd will
+work anyway.
4.60 KVM_DIRTY_TLB
@@ -1774,7 +1784,7 @@ has been called, this interface is completely emulated within the kernel.
To use this to emulate the LINT1 input with KVM_CREATE_IRQCHIP, use the
following algorithm:
- - pause the vpcu
+ - pause the vcpu
- read the local APIC's state (KVM_GET_LAPIC)
- check whether changing LINT1 will queue an NMI (see the LVT entry for LINT1)
- if so, issue KVM_NMI
@@ -2798,7 +2808,7 @@ Returns: = 0 on success,
< 0 on generic error (e.g. -EFAULT or -ENOMEM),
> 0 if an exception occurred while walking the page tables
-Read or write data from/to the logical (virtual) memory of a VPCU.
+Read or write data from/to the logical (virtual) memory of a VCPU.
Parameters are specified via the following structure:
@@ -3309,6 +3319,18 @@ Valid values for 'type' are:
to ignore the request, or to gather VM memory core dump and/or
reset/shutdown of the VM.
+ /* KVM_EXIT_IOAPIC_EOI */
+ struct {
+ __u8 vector;
+ } eoi;
+
+Indicates that the VCPU's in-kernel local APIC received an EOI for a
+level-triggered IOAPIC interrupt. This exit only triggers when the
+IOAPIC is implemented in userspace (i.e. KVM_CAP_SPLIT_IRQCHIP is enabled);
+the userspace IOAPIC should process the EOI and retrigger the interrupt if
+it is still asserted. Vector is the LAPIC interrupt vector for which the
+EOI was received.
+
/* Fix the size of the union. */
char padding[256];
};
@@ -3627,6 +3649,26 @@ struct {
KVM handlers should exit to userspace with rc = -EREMOTE.
+7.5 KVM_CAP_SPLIT_IRQCHIP
+
+Architectures: x86
+Parameters: args[0] - number of routes reserved for userspace IOAPICs
+Returns: 0 on success, -1 on error
+
+Create a local apic for each processor in the kernel. This can be used
+instead of KVM_CREATE_IRQCHIP if the userspace VMM wishes to emulate the
+IOAPIC and PIC (and also the PIT, even though this has to be enabled
+separately).
+
+This capability also enables in kernel routing of interrupt requests;
+when KVM_CAP_SPLIT_IRQCHIP only routes of KVM_IRQ_ROUTING_MSI type are
+used in the IRQ routing table. The first args[0] MSI routes are reserved
+for the IOAPIC pins. Whenever the LAPIC receives an EOI for these routes,
+a KVM_EXIT_IOAPIC_EOI vmexit will be reported to userspace.
+
+Fails if VCPU has already been created, or if the irqchip is already in the
+kernel (i.e. KVM_CREATE_IRQCHIP has already been called).
+
8. Other capabilities.
----------------------
diff --git a/Documentation/virtual/kvm/arm/vgic-mapped-irqs.txt b/Documentation/virtual/kvm/arm/vgic-mapped-irqs.txt
new file mode 100644
index 000000000..38bca2835
--- /dev/null
+++ b/Documentation/virtual/kvm/arm/vgic-mapped-irqs.txt
@@ -0,0 +1,187 @@
+KVM/ARM VGIC Forwarded Physical Interrupts
+==========================================
+
+The KVM/ARM code implements software support for the ARM Generic
+Interrupt Controller's (GIC's) hardware support for virtualization by
+allowing software to inject virtual interrupts to a VM, which the guest
+OS sees as regular interrupts. The code is famously known as the VGIC.
+
+Some of these virtual interrupts, however, correspond to physical
+interrupts from real physical devices. One example could be the
+architected timer, which itself supports virtualization, and therefore
+lets a guest OS program the hardware device directly to raise an
+interrupt at some point in time. When such an interrupt is raised, the
+host OS initially handles the interrupt and must somehow signal this
+event as a virtual interrupt to the guest. Another example could be a
+passthrough device, where the physical interrupts are initially handled
+by the host, but the device driver for the device lives in the guest OS
+and KVM must therefore somehow inject a virtual interrupt on behalf of
+the physical one to the guest OS.
+
+These virtual interrupts corresponding to a physical interrupt on the
+host are called forwarded physical interrupts, but are also sometimes
+referred to as 'virtualized physical interrupts' and 'mapped interrupts'.
+
+Forwarded physical interrupts are handled slightly differently compared
+to virtual interrupts generated purely by a software emulated device.
+
+
+The HW bit
+----------
+Virtual interrupts are signalled to the guest by programming the List
+Registers (LRs) on the GIC before running a VCPU. The LR is programmed
+with the virtual IRQ number and the state of the interrupt (Pending,
+Active, or Pending+Active). When the guest ACKs and EOIs a virtual
+interrupt, the LR state moves from Pending to Active, and finally to
+inactive.
+
+The LRs include an extra bit, called the HW bit. When this bit is set,
+KVM must also program an additional field in the LR, the physical IRQ
+number, to link the virtual with the physical IRQ.
+
+When the HW bit is set, KVM must EITHER set the Pending OR the Active
+bit, never both at the same time.
+
+Setting the HW bit causes the hardware to deactivate the physical
+interrupt on the physical distributor when the guest deactivates the
+corresponding virtual interrupt.
+
+
+Forwarded Physical Interrupts Life Cycle
+----------------------------------------
+
+The state of forwarded physical interrupts is managed in the following way:
+
+ - The physical interrupt is acked by the host, and becomes active on
+ the physical distributor (*).
+ - KVM sets the LR.Pending bit, because this is the only way the GICV
+ interface is going to present it to the guest.
+ - LR.Pending will stay set as long as the guest has not acked the interrupt.
+ - LR.Pending transitions to LR.Active on the guest read of the IAR, as
+ expected.
+ - On guest EOI, the *physical distributor* active bit gets cleared,
+ but the LR.Active is left untouched (set).
+ - KVM clears the LR on VM exits when the physical distributor
+ active state has been cleared.
+
+(*): The host handling is slightly more complicated. For some forwarded
+interrupts (shared), KVM directly sets the active state on the physical
+distributor before entering the guest, because the interrupt is never actually
+handled on the host (see details on the timer as an example below). For other
+forwarded interrupts (non-shared) the host does not deactivate the interrupt
+when the host ISR completes, but leaves the interrupt active until the guest
+deactivates it. Leaving the interrupt active is allowed, because Linux
+configures the physical GIC with EOIMode=1, which causes EOI operations to
+perform a priority drop allowing the GIC to receive other interrupts of the
+default priority.
+
+
+Forwarded Edge and Level Triggered PPIs and SPIs
+------------------------------------------------
+Forwarded physical interrupts injected should always be active on the
+physical distributor when injected to a guest.
+
+Level-triggered interrupts will keep the interrupt line to the GIC
+asserted, typically until the guest programs the device to deassert the
+line. This means that the interrupt will remain pending on the physical
+distributor until the guest has reprogrammed the device. Since we
+always run the VM with interrupts enabled on the CPU, a pending
+interrupt will exit the guest as soon as we switch into the guest,
+preventing the guest from ever making progress as the process repeats
+over and over. Therefore, the active state on the physical distributor
+must be set when entering the guest, preventing the GIC from forwarding
+the pending interrupt to the CPU. As soon as the guest deactivates the
+interrupt, the physical line is sampled by the hardware again and the host
+takes a new interrupt if and only if the physical line is still asserted.
+
+Edge-triggered interrupts do not exhibit the same problem with
+preventing guest execution that level-triggered interrupts do. One
+option is to not use HW bit at all, and inject edge-triggered interrupts
+from a physical device as pure virtual interrupts. But that would
+potentially slow down handling of the interrupt in the guest, because a
+physical interrupt occurring in the middle of the guest ISR would
+preempt the guest for the host to handle the interrupt. Additionally,
+if you configure the system to handle interrupts on a separate physical
+core from that running your VCPU, you still have to interrupt the VCPU
+to queue the pending state onto the LR, even though the guest won't use
+this information until the guest ISR completes. Therefore, the HW
+bit should always be set for forwarded edge-triggered interrupts. With
+the HW bit set, the virtual interrupt is injected and additional
+physical interrupts occurring before the guest deactivates the interrupt
+simply mark the state on the physical distributor as Pending+Active. As
+soon as the guest deactivates the interrupt, the host takes another
+interrupt if and only if there was a physical interrupt between injecting
+the forwarded interrupt to the guest and the guest deactivating the
+interrupt.
+
+Consequently, whenever we schedule a VCPU with one or more LRs with the
+HW bit set, the interrupt must also be active on the physical
+distributor.
+
+
+Forwarded LPIs
+--------------
+LPIs, introduced in GICv3, are always edge-triggered and do not have an
+active state. They become pending when a device signal them, and as
+soon as they are acked by the CPU, they are inactive again.
+
+It therefore doesn't make sense, and is not supported, to set the HW bit
+for physical LPIs that are forwarded to a VM as virtual interrupts,
+typically virtual SPIs.
+
+For LPIs, there is no other choice than to preempt the VCPU thread if
+necessary, and queue the pending state onto the LR.
+
+
+Putting It Together: The Architected Timer
+------------------------------------------
+The architected timer is a device that signals interrupts with level
+triggered semantics. The timer hardware is directly accessed by VCPUs
+which program the timer to fire at some point in time. Each VCPU on a
+system programs the timer to fire at different times, and therefore the
+hardware is multiplexed between multiple VCPUs. This is implemented by
+context-switching the timer state along with each VCPU thread.
+
+However, this means that a scenario like the following is entirely
+possible, and in fact, typical:
+
+1. KVM runs the VCPU
+2. The guest programs the time to fire in T+100
+3. The guest is idle and calls WFI (wait-for-interrupts)
+4. The hardware traps to the host
+5. KVM stores the timer state to memory and disables the hardware timer
+6. KVM schedules a soft timer to fire in T+(100 - time since step 2)
+7. KVM puts the VCPU thread to sleep (on a waitqueue)
+8. The soft timer fires, waking up the VCPU thread
+9. KVM reprograms the timer hardware with the VCPU's values
+10. KVM marks the timer interrupt as active on the physical distributor
+11. KVM injects a forwarded physical interrupt to the guest
+12. KVM runs the VCPU
+
+Notice that KVM injects a forwarded physical interrupt in step 11 without
+the corresponding interrupt having actually fired on the host. That is
+exactly why we mark the timer interrupt as active in step 10, because
+the active state on the physical distributor is part of the state
+belonging to the timer hardware, which is context-switched along with
+the VCPU thread.
+
+If the guest does not idle because it is busy, the flow looks like this
+instead:
+
+1. KVM runs the VCPU
+2. The guest programs the time to fire in T+100
+4. At T+100 the timer fires and a physical IRQ causes the VM to exit
+ (note that this initially only traps to EL2 and does not run the host ISR
+ until KVM has returned to the host).
+5. With interrupts still disabled on the CPU coming back from the guest, KVM
+ stores the virtual timer state to memory and disables the virtual hw timer.
+6. KVM looks at the timer state (in memory) and injects a forwarded physical
+ interrupt because it concludes the timer has expired.
+7. KVM marks the timer interrupt as active on the physical distributor
+7. KVM enables the timer, enables interrupts, and runs the VCPU
+
+Notice that again the forwarded physical interrupt is injected to the
+guest without having actually been handled on the host. In this case it
+is because the physical interrupt is never actually seen by the host because the
+timer is disabled upon guest return, and the virtual forwarded interrupt is
+injected on the KVM guest entry path.
diff --git a/Documentation/virtual/kvm/devices/arm-vgic.txt b/Documentation/virtual/kvm/devices/arm-vgic.txt
index 3fb905429..59541d49e 100644
--- a/Documentation/virtual/kvm/devices/arm-vgic.txt
+++ b/Documentation/virtual/kvm/devices/arm-vgic.txt
@@ -44,28 +44,29 @@ Groups:
Attributes:
The attr field of kvm_device_attr encodes two values:
bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
- values: | reserved | cpu id | offset |
+ values: | reserved | vcpu_index | offset |
All distributor regs are (rw, 32-bit)
The offset is relative to the "Distributor base address" as defined in the
GICv2 specs. Getting or setting such a register has the same effect as
- reading or writing the register on the actual hardware from the cpu
- specified with cpu id field. Note that most distributor fields are not
- banked, but return the same value regardless of the cpu id used to access
- the register.
+ reading or writing the register on the actual hardware from the cpu whose
+ index is specified with the vcpu_index field. Note that most distributor
+ fields are not banked, but return the same value regardless of the
+ vcpu_index used to access the register.
Limitations:
- Priorities are not implemented, and registers are RAZ/WI
- Currently only implemented for KVM_DEV_TYPE_ARM_VGIC_V2.
Errors:
- -ENODEV: Getting or setting this register is not yet supported
+ -ENXIO: Getting or setting this register is not yet supported
-EBUSY: One or more VCPUs are running
+ -EINVAL: Invalid vcpu_index supplied
KVM_DEV_ARM_VGIC_GRP_CPU_REGS
Attributes:
The attr field of kvm_device_attr encodes two values:
bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
- values: | reserved | cpu id | offset |
+ values: | reserved | vcpu_index | offset |
All CPU interface regs are (rw, 32-bit)
@@ -91,8 +92,9 @@ Groups:
- Priorities are not implemented, and registers are RAZ/WI
- Currently only implemented for KVM_DEV_TYPE_ARM_VGIC_V2.
Errors:
- -ENODEV: Getting or setting this register is not yet supported
+ -ENXIO: Getting or setting this register is not yet supported
-EBUSY: One or more VCPUs are running
+ -EINVAL: Invalid vcpu_index supplied
KVM_DEV_ARM_VGIC_GRP_NR_IRQS
Attributes:
diff --git a/Documentation/virtual/kvm/devices/vm.txt b/Documentation/virtual/kvm/devices/vm.txt
index 5542c4641..2d09d1ed8 100644
--- a/Documentation/virtual/kvm/devices/vm.txt
+++ b/Documentation/virtual/kvm/devices/vm.txt
@@ -74,7 +74,7 @@ struct kvm_s390_vm_cpu_processor {
KVM does not enforce or limit the cpu model data in any form. Take the information
retrieved by means of KVM_S390_VM_CPU_MACHINE as hint for reasonable configuration
-setups. Instruction interceptions triggered by additionally set facilitiy bits that
+setups. Instruction interceptions triggered by additionally set facility bits that
are not handled by KVM need to by imlemented in the VM driver code.
Parameters: address of buffer to store/set the processor related cpu
diff --git a/Documentation/virtual/kvm/locking.txt b/Documentation/virtual/kvm/locking.txt
index d68af4dc3..19f94a6b9 100644
--- a/Documentation/virtual/kvm/locking.txt
+++ b/Documentation/virtual/kvm/locking.txt
@@ -166,3 +166,15 @@ Comment: The srcu read lock must be held while accessing memslots (e.g.
MMIO/PIO address->device structure mapping (kvm->buses).
The srcu index can be stored in kvm_vcpu->srcu_idx per vcpu
if it is needed by multiple functions.
+
+Name: blocked_vcpu_on_cpu_lock
+Type: spinlock_t
+Arch: x86
+Protects: blocked_vcpu_on_cpu
+Comment: This is a per-CPU lock and it is used for VT-d posted-interrupts.
+ When VT-d posted-interrupts is supported and the VM has assigned
+ devices, we put the blocked vCPU on the list blocked_vcpu_on_cpu
+ protected by blocked_vcpu_on_cpu_lock, when VT-d hardware issues
+ wakeup notification event since external interrupts from the
+ assigned devices happens, we will find the vCPU on the list to
+ wakeup.
diff --git a/Documentation/virtual/kvm/ppc-pv.txt b/Documentation/virtual/kvm/ppc-pv.txt
index 319560646..e26115ce4 100644
--- a/Documentation/virtual/kvm/ppc-pv.txt
+++ b/Documentation/virtual/kvm/ppc-pv.txt
@@ -110,7 +110,7 @@ Flags are passed to the host in the low 12 bits of the Effective Address.
The following flags are currently available for a guest to expose:
- MAGIC_PAGE_FLAG_NOT_MAPPED_NX Guest handles NX bits correclty wrt magic page
+ MAGIC_PAGE_FLAG_NOT_MAPPED_NX Guest handles NX bits correctly wrt magic page
MSR bits
========