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authorLinus Torvalds <torvalds@linux-foundation.org>2019-03-31 08:55:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-31 08:55:59 -0700
commit63fc9c23488d6cf34e4c233e24ba59b7e5548412 (patch)
tree08188f35d8625be520730e4ae106e8af2ee7b058 /Documentation
parent915ee0da5ecb7ac7fd023ae36f01c47ce47a45d1 (diff)
parent690edec54cbaa0e98dc592aae6864272f48f3c84 (diff)
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull KVM fixes from Paolo Bonzini: "A collection of x86 and ARM bugfixes, and some improvements to documentation. On top of this, a cleanup of kvm_para.h headers, which were exported by some architectures even though they not support KVM at all. This is responsible for all the Kbuild changes in the diffstat" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (28 commits) Documentation: kvm: clarify KVM_SET_USER_MEMORY_REGION KVM: doc: Document the life cycle of a VM and its resources KVM: selftests: complete IO before migrating guest state KVM: selftests: disable stack protector for all KVM tests KVM: selftests: explicitly disable PIE for tests KVM: selftests: assert on exit reason in CR4/cpuid sync test KVM: x86: update %rip after emulating IO x86/kvm/hyper-v: avoid spurious pending stimer on vCPU init kvm/x86: Move MSR_IA32_ARCH_CAPABILITIES to array emulated_msrs KVM: x86: Emulate MSR_IA32_ARCH_CAPABILITIES on AMD hosts kvm: don't redefine flags as something else kvm: mmu: Used range based flushing in slot_handle_level_range KVM: export <linux/kvm_para.h> and <asm/kvm_para.h> iif KVM is supported KVM: x86: remove check on nr_mmu_pages in kvm_arch_commit_memory_region() kvm: nVMX: Add a vmentry check for HOST_SYSENTER_ESP and HOST_SYSENTER_EIP fields KVM: SVM: Workaround errata#1096 (insn_len maybe zero on SMAP violation) KVM: Reject device ioctls from processes other than the VM's creator KVM: doc: Fix incorrect word ordering regarding supported use of APIs KVM: x86: fix handling of role.cr4_pae and rename it to 'gpte_size' KVM: nVMX: Do not inherit quadrant and invalid for the root shadow EPT ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/virtual/kvm/api.txt77
-rw-r--r--Documentation/virtual/kvm/mmu.txt11
2 files changed, 60 insertions, 28 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 7de9eee73fcd..67068c47c591 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -5,25 +5,32 @@ The Definitive KVM (Kernel-based Virtual Machine) API Documentation
----------------------
The kvm API is a set of ioctls that are issued to control various aspects
-of a virtual machine. The ioctls belong to three classes
+of a virtual machine. The ioctls belong to three classes:
- System ioctls: These query and set global attributes which affect the
whole kvm subsystem. In addition a system ioctl is used to create
- virtual machines
+ virtual machines.
- VM ioctls: These query and set attributes that affect an entire virtual
machine, for example memory layout. In addition a VM ioctl is used to
- create virtual cpus (vcpus).
+ create virtual cpus (vcpus) and devices.
- Only run VM ioctls from the same process (address space) that was used
- to create the VM.
+ VM ioctls must be issued from the same process (address space) that was
+ used to create the VM.
- vcpu ioctls: These query and set attributes that control the operation
of a single virtual cpu.
- Only run vcpu ioctls from the same thread that was used to create the
- vcpu.
+ vcpu ioctls should be issued from the same thread that was used to create
+ the vcpu, except for asynchronous vcpu ioctl that are marked as such in
+ the documentation. Otherwise, the first ioctl after switching threads
+ could see a performance impact.
+ - device ioctls: These query and set attributes that control the operation
+ of a single device.
+
+ device ioctls must be issued from the same process (address space) that
+ was used to create the VM.
2. File descriptors
-------------------
@@ -32,17 +39,34 @@ The kvm API is centered around file descriptors. An initial
open("/dev/kvm") obtains a handle to the kvm subsystem; this handle
can be used to issue system ioctls. A KVM_CREATE_VM ioctl on this
handle will create a VM file descriptor which can be used to issue VM
-ioctls. A KVM_CREATE_VCPU ioctl on a VM fd will create a virtual cpu
-and return a file descriptor pointing to it. Finally, ioctls on a vcpu
-fd can be used to control the vcpu, including the important task of
-actually running guest code.
+ioctls. A KVM_CREATE_VCPU or KVM_CREATE_DEVICE ioctl on a VM fd will
+create a virtual cpu or device and return a file descriptor pointing to
+the new resource. Finally, ioctls on a vcpu or device fd can be used
+to control the vcpu or device. For vcpus, this includes the important
+task of actually running guest code.
In general file descriptors can be migrated among processes by means
of fork() and the SCM_RIGHTS facility of unix domain socket. These
kinds of tricks are explicitly not supported by kvm. While they will
not cause harm to the host, their actual behavior is not guaranteed by
-the API. The only supported use is one virtual machine per process,
-and one vcpu per thread.
+the API. See "General description" for details on the ioctl usage
+model that is supported by KVM.
+
+It is important to note that althought VM ioctls may only be issued from
+the process that created the VM, a VM's lifecycle is associated with its
+file descriptor, not its creator (process). In other words, the VM and
+its resources, *including the associated address space*, are not freed
+until the last reference to the VM's file descriptor has been released.
+For example, if fork() is issued after ioctl(KVM_CREATE_VM), the VM will
+not be freed until both the parent (original) process and its child have
+put their references to the VM's file descriptor.
+
+Because a VM's resources are not freed until the last reference to its
+file descriptor is released, creating additional references to a VM via
+via fork(), dup(), etc... without careful consideration is strongly
+discouraged and may have unwanted side effects, e.g. memory allocated
+by and on behalf of the VM's process may not be freed/unaccounted when
+the VM is shut down.
It is important to note that althought VM ioctls may only be issued from
@@ -515,11 +539,15 @@ c) KVM_INTERRUPT_SET_LEVEL
Note that any value for 'irq' other than the ones stated above is invalid
and incurs unexpected behavior.
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+
MIPS:
Queues an external interrupt to be injected into the virtual CPU. A negative
interrupt number dequeues the interrupt.
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+
4.17 KVM_DEBUG_GUEST
@@ -1086,14 +1114,12 @@ struct kvm_userspace_memory_region {
#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
#define KVM_MEM_READONLY (1UL << 1)
-This ioctl allows the user to create or modify a guest physical memory
-slot. When changing an existing slot, it may be moved in the guest
-physical memory space, or its flags may be modified. It may not be
-resized. Slots may not overlap in guest physical address space.
-Bits 0-15 of "slot" specifies the slot id and this value should be
-less than the maximum number of user memory slots supported per VM.
-The maximum allowed slots can be queried using KVM_CAP_NR_MEMSLOTS,
-if this capability is supported by the architecture.
+This ioctl allows the user to create, modify or delete a guest physical
+memory slot. Bits 0-15 of "slot" specify the slot id and this value
+should be less than the maximum number of user memory slots supported per
+VM. The maximum allowed slots can be queried using KVM_CAP_NR_MEMSLOTS,
+if this capability is supported by the architecture. Slots may not
+overlap in guest physical address space.
If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 of "slot"
specifies the address space which is being modified. They must be
@@ -1102,6 +1128,10 @@ KVM_CAP_MULTI_ADDRESS_SPACE capability. Slots in separate address spaces
are unrelated; the restriction on overlapping slots only applies within
each address space.
+Deleting a slot is done by passing zero for memory_size. When changing
+an existing slot, it may be moved in the guest physical memory space,
+or its flags may be modified, but it may not be resized.
+
Memory for the region is taken starting at the address denoted by the
field userspace_addr, which must point at user addressable memory for
the entire memory slot size. Any object may back this memory, including
@@ -2493,7 +2523,7 @@ KVM_S390_MCHK (vm, vcpu) - machine check interrupt; cr 14 bits in parm,
machine checks needing further payload are not
supported by this ioctl)
-Note that the vcpu ioctl is asynchronous to vcpu execution.
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
4.78 KVM_PPC_GET_HTAB_FD
@@ -3042,8 +3072,7 @@ KVM_S390_INT_EMERGENCY - sigp emergency; parameters in .emerg
KVM_S390_INT_EXTERNAL_CALL - sigp external call; parameters in .extcall
KVM_S390_MCHK - machine check interrupt; parameters in .mchk
-
-Note that the vcpu ioctl is asynchronous to vcpu execution.
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
4.94 KVM_S390_GET_IRQ_STATE
diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
index f365102c80f5..2efe0efc516e 100644
--- a/Documentation/virtual/kvm/mmu.txt
+++ b/Documentation/virtual/kvm/mmu.txt
@@ -142,7 +142,7 @@ Shadow pages contain the following information:
If clear, this page corresponds to a guest page table denoted by the gfn
field.
role.quadrant:
- When role.cr4_pae=0, the guest uses 32-bit gptes while the host uses 64-bit
+ When role.gpte_is_8_bytes=0, the guest uses 32-bit gptes while the host uses 64-bit
sptes. That means a guest page table contains more ptes than the host,
so multiple shadow pages are needed to shadow one guest page.
For first-level shadow pages, role.quadrant can be 0 or 1 and denotes the
@@ -158,9 +158,9 @@ Shadow pages contain the following information:
The page is invalid and should not be used. It is a root page that is
currently pinned (by a cpu hardware register pointing to it); once it is
unpinned it will be destroyed.
- role.cr4_pae:
- Contains the value of cr4.pae for which the page is valid (e.g. whether
- 32-bit or 64-bit gptes are in use).
+ role.gpte_is_8_bytes:
+ Reflects the size of the guest PTE for which the page is valid, i.e. '1'
+ if 64-bit gptes are in use, '0' if 32-bit gptes are in use.
role.nxe:
Contains the value of efer.nxe for which the page is valid.
role.cr0_wp:
@@ -173,6 +173,9 @@ Shadow pages contain the following information:
Contains the value of cr4.smap && !cr0.wp for which the page is valid
(pages for which this is true are different from other pages; see the
treatment of cr0.wp=0 below).
+ role.ept_sp:
+ This is a virtual flag to denote a shadowed nested EPT page. ept_sp
+ is true if "cr0_wp && smap_andnot_wp", an otherwise invalid combination.
role.smm:
Is 1 if the page is valid in system management mode. This field
determines which of the kvm_memslots array was used to build this