diff options
Diffstat (limited to 'Documentation/virtual')
| -rw-r--r-- | Documentation/virtual/kvm/api.txt | 66 | ||||
| -rw-r--r-- | Documentation/virtual/kvm/mmu.txt | 91 | ||||
| -rw-r--r-- | Documentation/virtual/uml/UserModeLinux-HOWTO.txt | 4 |
3 files changed, 128 insertions, 33 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 5f91eda91647..66dd2aa53ba4 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -280,7 +280,7 @@ kvm_run' (see below). 4.11 KVM_GET_REGS Capability: basic -Architectures: all except ARM +Architectures: all except ARM, arm64 Type: vcpu ioctl Parameters: struct kvm_regs (out) Returns: 0 on success, -1 on error @@ -301,7 +301,7 @@ struct kvm_regs { 4.12 KVM_SET_REGS Capability: basic -Architectures: all except ARM +Architectures: all except ARM, arm64 Type: vcpu ioctl Parameters: struct kvm_regs (in) Returns: 0 on success, -1 on error @@ -587,7 +587,7 @@ struct kvm_fpu { 4.24 KVM_CREATE_IRQCHIP Capability: KVM_CAP_IRQCHIP -Architectures: x86, ia64, ARM +Architectures: x86, ia64, ARM, arm64 Type: vm ioctl Parameters: none Returns: 0 on success, -1 on error @@ -595,14 +595,14 @@ Returns: 0 on success, -1 on error Creates an interrupt controller model in the kernel. On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up future vcpus to have a local APIC. IRQ routing for GSIs 0-15 is set to both PIC and IOAPIC; GSI 16-23 -only go to the IOAPIC. On ia64, a IOSAPIC is created. On ARM, a GIC is +only go to the IOAPIC. On ia64, a IOSAPIC is created. On ARM/arm64, a GIC is created. 4.25 KVM_IRQ_LINE Capability: KVM_CAP_IRQCHIP -Architectures: x86, ia64, arm +Architectures: x86, ia64, arm, arm64 Type: vm ioctl Parameters: struct kvm_irq_level Returns: 0 on success, -1 on error @@ -612,9 +612,10 @@ On some architectures it is required that an interrupt controller model has been previously created with KVM_CREATE_IRQCHIP. Note that edge-triggered interrupts require the level to be set to 1 and then back to 0. -ARM can signal an interrupt either at the CPU level, or at the in-kernel irqchip -(GIC), and for in-kernel irqchip can tell the GIC to use PPIs designated for -specific cpus. The irq field is interpreted like this: +ARM/arm64 can signal an interrupt either at the CPU level, or at the +in-kernel irqchip (GIC), and for in-kernel irqchip can tell the GIC to +use PPIs designated for specific cpus. The irq field is interpreted +like this: bits: | 31 ... 24 | 23 ... 16 | 15 ... 0 | field: | irq_type | vcpu_index | irq_id | @@ -1831,6 +1832,22 @@ ARM 32-bit VFP control registers have the following id bit patterns: ARM 64-bit FP registers have the following id bit patterns: 0x4030 0000 0012 0 <regno:12> + +arm64 registers are mapped using the lower 32 bits. The upper 16 of +that is the register group type, or coprocessor number: + +arm64 core/FP-SIMD registers have the following id bit patterns. Note +that the size of the access is variable, as the kvm_regs structure +contains elements ranging from 32 to 128 bits. The index is a 32bit +value in the kvm_regs structure seen as a 32bit array. + 0x60x0 0000 0010 <index into the kvm_regs struct:16> + +arm64 CCSIDR registers are demultiplexed by CSSELR value: + 0x6020 0000 0011 00 <csselr:8> + +arm64 system registers have the following id bit patterns: + 0x6030 0000 0013 <op0:2> <op1:3> <crn:4> <crm:4> <op2:3> + 4.69 KVM_GET_ONE_REG Capability: KVM_CAP_ONE_REG @@ -2261,10 +2278,10 @@ return indicates the attribute is implemented. It does not necessarily indicate that the attribute can be read or written in the device's current state. "addr" is ignored. -4.77 KVM_ARM_VCPU_INIT +4.82 KVM_ARM_VCPU_INIT Capability: basic -Architectures: arm +Architectures: arm, arm64 Type: vcpu ioctl Parameters: struct struct kvm_vcpu_init (in) Returns: 0 on success; -1 on error @@ -2283,12 +2300,14 @@ should be created before this ioctl is invoked. Possible features: - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state. Depends on KVM_CAP_ARM_PSCI. + - KVM_ARM_VCPU_EL1_32BIT: Starts the CPU in a 32bit mode. + Depends on KVM_CAP_ARM_EL1_32BIT (arm64 only). -4.78 KVM_GET_REG_LIST +4.83 KVM_GET_REG_LIST Capability: basic -Architectures: arm +Architectures: arm, arm64 Type: vcpu ioctl Parameters: struct kvm_reg_list (in/out) Returns: 0 on success; -1 on error @@ -2305,10 +2324,10 @@ This ioctl returns the guest registers that are supported for the KVM_GET_ONE_REG/KVM_SET_ONE_REG calls. -4.80 KVM_ARM_SET_DEVICE_ADDR +4.84 KVM_ARM_SET_DEVICE_ADDR Capability: KVM_CAP_ARM_SET_DEVICE_ADDR -Architectures: arm +Architectures: arm, arm64 Type: vm ioctl Parameters: struct kvm_arm_device_address (in) Returns: 0 on success, -1 on error @@ -2329,20 +2348,21 @@ can access emulated or directly exposed devices, which the host kernel needs to know about. The id field is an architecture specific identifier for a specific device. -ARM divides the id field into two parts, a device id and an address type id -specific to the individual device. +ARM/arm64 divides the id field into two parts, a device id and an +address type id specific to the individual device. bits: | 63 ... 32 | 31 ... 16 | 15 ... 0 | field: | 0x00000000 | device id | addr type id | -ARM currently only require this when using the in-kernel GIC support for the -hardware VGIC features, using KVM_ARM_DEVICE_VGIC_V2 as the device id. When -setting the base address for the guest's mapping of the VGIC virtual CPU -and distributor interface, the ioctl must be called after calling -KVM_CREATE_IRQCHIP, but before calling KVM_RUN on any of the VCPUs. Calling -this ioctl twice for any of the base addresses will return -EEXIST. +ARM/arm64 currently only require this when using the in-kernel GIC +support for the hardware VGIC features, using KVM_ARM_DEVICE_VGIC_V2 +as the device id. When setting the base address for the guest's +mapping of the VGIC virtual CPU and distributor interface, the ioctl +must be called after calling KVM_CREATE_IRQCHIP, but before calling +KVM_RUN on any of the VCPUs. Calling this ioctl twice for any of the +base addresses will return -EEXIST. -4.82 KVM_PPC_RTAS_DEFINE_TOKEN +4.85 KVM_PPC_RTAS_DEFINE_TOKEN Capability: KVM_CAP_PPC_RTAS Architectures: ppc diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt index 43fcb761ed16..290894176142 100644 --- a/Documentation/virtual/kvm/mmu.txt +++ b/Documentation/virtual/kvm/mmu.txt @@ -191,12 +191,12 @@ Shadow pages contain the following information: A counter keeping track of how many hardware registers (guest cr3 or pdptrs) are now pointing at the page. While this counter is nonzero, the page cannot be destroyed. See role.invalid. - multimapped: - Whether there exist multiple sptes pointing at this page. - parent_pte/parent_ptes: - If multimapped is zero, parent_pte points at the single spte that points at - this page's spt. Otherwise, parent_ptes points at a data structure - with a list of parent_ptes. + parent_ptes: + The reverse mapping for the pte/ptes pointing at this page's spt. If + parent_ptes bit 0 is zero, only one spte points at this pages and + parent_ptes points at this single spte, otherwise, there exists multiple + sptes pointing at this page and (parent_ptes & ~0x1) points at a data + structure with a list of parent_ptes. unsync: If true, then the translations in this page may not match the guest's translation. This is equivalent to the state of the tlb when a pte is @@ -210,6 +210,24 @@ Shadow pages contain the following information: A bitmap indicating which sptes in spt point (directly or indirectly) at pages that may be unsynchronized. Used to quickly locate all unsychronized pages reachable from a given page. + mmu_valid_gen: + Generation number of the page. It is compared with kvm->arch.mmu_valid_gen + during hash table lookup, and used to skip invalidated shadow pages (see + "Zapping all pages" below.) + clear_spte_count: + Only present on 32-bit hosts, where a 64-bit spte cannot be written + atomically. The reader uses this while running out of the MMU lock + to detect in-progress updates and retry them until the writer has + finished the write. + write_flooding_count: + A guest may write to a page table many times, causing a lot of + emulations if the page needs to be write-protected (see "Synchronized + and unsynchronized pages" below). Leaf pages can be unsynchronized + so that they do not trigger frequent emulation, but this is not + possible for non-leafs. This field counts the number of emulations + since the last time the page table was actually used; if emulation + is triggered too frequently on this page, KVM will unmap the page + to avoid emulation in the future. Reverse map =========== @@ -258,14 +276,26 @@ This is the most complicated event. The cause of a page fault can be: Handling a page fault is performed as follows: + - if the RSV bit of the error code is set, the page fault is caused by guest + accessing MMIO and cached MMIO information is available. + - walk shadow page table + - check for valid generation number in the spte (see "Fast invalidation of + MMIO sptes" below) + - cache the information to vcpu->arch.mmio_gva, vcpu->arch.access and + vcpu->arch.mmio_gfn, and call the emulator + - If both P bit and R/W bit of error code are set, this could possibly + be handled as a "fast page fault" (fixed without taking the MMU lock). See + the description in Documentation/virtual/kvm/locking.txt. - if needed, walk the guest page tables to determine the guest translation (gva->gpa or ngpa->gpa) - if permissions are insufficient, reflect the fault back to the guest - determine the host page - - if this is an mmio request, there is no host page; call the emulator - to emulate the instruction instead + - if this is an mmio request, there is no host page; cache the info to + vcpu->arch.mmio_gva, vcpu->arch.access and vcpu->arch.mmio_gfn - walk the shadow page table to find the spte for the translation, instantiating missing intermediate page tables as necessary + - If this is an mmio request, cache the mmio info to the spte and set some + reserved bit on the spte (see callers of kvm_mmu_set_mmio_spte_mask) - try to unsynchronize the page - if successful, we can let the guest continue and modify the gpte - emulate the instruction @@ -351,6 +381,51 @@ causes its write_count to be incremented, thus preventing instantiation of a large spte. The frames at the end of an unaligned memory slot have artificially inflated ->write_counts so they can never be instantiated. +Zapping all pages (page generation count) +========================================= + +For the large memory guests, walking and zapping all pages is really slow +(because there are a lot of pages), and also blocks memory accesses of +all VCPUs because it needs to hold the MMU lock. + +To make it be more scalable, kvm maintains a global generation number +which is stored in kvm->arch.mmu_valid_gen. Every shadow page stores +the current global generation-number into sp->mmu_valid_gen when it +is created. Pages with a mismatching generation number are "obsolete". + +When KVM need zap all shadow pages sptes, it just simply increases the global +generation-number then reload root shadow pages on all vcpus. As the VCPUs +create new shadow page tables, the old pages are not used because of the +mismatching generation number. + +KVM then walks through all pages and zaps obsolete pages. While the zap +operation needs to take the MMU lock, the lock can be released periodically +so that the VCPUs can make progress. + +Fast invalidation of MMIO sptes +=============================== + +As mentioned in "Reaction to events" above, kvm will cache MMIO +information in leaf sptes. When a new memslot is added or an existing +memslot is changed, this information may become stale and needs to be +invalidated. This also needs to hold the MMU lock while walking all +shadow pages, and is made more scalable with a similar technique. + +MMIO sptes have a few spare bits, which are used to store a +generation number. The global generation number is stored in +kvm_memslots(kvm)->generation, and increased whenever guest memory info +changes. This generation number is distinct from the one described in +the previous section. + +When KVM finds an MMIO spte, it checks the generation number of the spte. +If the generation number of the spte does not equal the global generation +number, it will ignore the cached MMIO information and handle the page +fault through the slow path. + +Since only 19 bits are used to store generation-number on mmio spte, all +pages are zapped when there is an overflow. + + Further reading =============== diff --git a/Documentation/virtual/uml/UserModeLinux-HOWTO.txt b/Documentation/virtual/uml/UserModeLinux-HOWTO.txt index a5f8436753e7..f4099ca6b483 100644 --- a/Documentation/virtual/uml/UserModeLinux-HOWTO.txt +++ b/Documentation/virtual/uml/UserModeLinux-HOWTO.txt @@ -3127,7 +3127,7 @@ at process_kern.c:156 #3 0x1006a052 in switch_to (prev=0x50072000, next=0x507e8000, last=0x50072000) at process_kern.c:161 - #4 0x10001d12 in schedule () at sched.c:777 + #4 0x10001d12 in schedule () at core.c:777 #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71 #6 0x1006aa10 in __down_failed () at semaphore.c:157 #7 0x1006c5d8 in segv_handler (sc=0x5006e940) at trap_user.c:174 @@ -3191,7 +3191,7 @@ at process_kern.c:161 161 _switch_to(prev, next); (gdb) - #4 0x10001d12 in schedule () at sched.c:777 + #4 0x10001d12 in schedule () at core.c:777 777 switch_to(prev, next, prev); (gdb) #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71 |