diff options
Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/guest-halt-polling.rst | 2 | ||||
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 29 | ||||
| -rw-r--r-- | Documentation/virt/kvm/halt-polling.rst | 10 | ||||
| -rw-r--r-- | Documentation/virt/kvm/locking.rst | 18 | ||||
| -rw-r--r-- | Documentation/virt/kvm/ppc-pv.rst | 8 | ||||
| -rw-r--r-- | Documentation/virt/kvm/vcpu-requests.rst | 6 | ||||
| -rw-r--r-- | Documentation/virt/kvm/x86/amd-memory-encryption.rst | 2 | ||||
| -rw-r--r-- | Documentation/virt/kvm/x86/mmu.rst | 2 | ||||
| -rw-r--r-- | Documentation/virt/paravirt_ops.rst | 16 |
9 files changed, 60 insertions, 33 deletions
diff --git a/Documentation/virt/guest-halt-polling.rst b/Documentation/virt/guest-halt-polling.rst index b4e747942417..922291ddc40c 100644 --- a/Documentation/virt/guest-halt-polling.rst +++ b/Documentation/virt/guest-halt-polling.rst @@ -72,7 +72,7 @@ high once achieves global guest_halt_poll_ns value). Default: Y -The module parameters can be set from the debugfs files in:: +The module parameters can be set from the sysfs files in:: /sys/module/haltpoll/parameters/ diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index add067793b90..c0ddd3035462 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -2613,7 +2613,7 @@ follows:: this vcpu, and determines which register slices are visible through this ioctl interface. -(See Documentation/arm64/sve.rst for an explanation of the "vq" +(See Documentation/arch/arm64/sve.rst for an explanation of the "vq" nomenclature.) KVM_REG_ARM64_SVE_VLS is only accessible after KVM_ARM_VCPU_INIT. @@ -8445,6 +8445,33 @@ structure. When getting the Modified Change Topology Report value, the attr->addr must point to a byte where the value will be stored or retrieved from. +8.40 KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +--------------------------------------- + +:Capability: KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +:Architectures: arm64 +:Type: vm +:Parameters: arg[0] is the new split chunk size. +:Returns: 0 on success, -EINVAL if any memslot was already created. + +This capability sets the chunk size used in Eager Page Splitting. + +Eager Page Splitting improves the performance of dirty-logging (used +in live migrations) when guest memory is backed by huge-pages. It +avoids splitting huge-pages (into PAGE_SIZE pages) on fault, by doing +it eagerly when enabling dirty logging (with the +KVM_MEM_LOG_DIRTY_PAGES flag for a memory region), or when using +KVM_CLEAR_DIRTY_LOG. + +The chunk size specifies how many pages to break at a time, using a +single allocation for each chunk. Bigger the chunk size, more pages +need to be allocated ahead of time. + +The chunk size needs to be a valid block size. The list of acceptable +block sizes is exposed in KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES as a +64-bit bitmap (each bit describing a block size). The default value is +0, to disable the eager page splitting. + 9. Known KVM API problems ========================= diff --git a/Documentation/virt/kvm/halt-polling.rst b/Documentation/virt/kvm/halt-polling.rst index 3fae39b1a5ba..4f1a1b23d99c 100644 --- a/Documentation/virt/kvm/halt-polling.rst +++ b/Documentation/virt/kvm/halt-polling.rst @@ -112,11 +112,11 @@ powerpc kvm-hv case. | | function. | | +-----------------------+---------------------------+-------------------------+ -These module parameters can be set from the debugfs files in: +These module parameters can be set from the sysfs files in: /sys/module/kvm/parameters/ -Note: that these module parameters are system wide values and are not able to +Note: these module parameters are system-wide values and are not able to be tuned on a per vm basis. Any changes to these parameters will be picked up by new and existing vCPUs the @@ -142,12 +142,12 @@ Further Notes global max polling interval (halt_poll_ns) then the host will always poll for the entire block time and thus cpu utilisation will go to 100%. -- Halt polling essentially presents a trade off between power usage and latency and +- Halt polling essentially presents a trade-off between power usage and latency and the module parameters should be used to tune the affinity for this. Idle cpu time is essentially converted to host kernel time with the aim of decreasing latency when entering the guest. - Halt polling will only be conducted by the host when no other tasks are runnable on that cpu, otherwise the polling will cease immediately and schedule will be invoked to - allow that other task to run. Thus this doesn't allow a guest to denial of service the - cpu. + allow that other task to run. Thus this doesn't allow a guest to cause denial of service + of the cpu. diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst index 8c77554e4896..3a034db5e55f 100644 --- a/Documentation/virt/kvm/locking.rst +++ b/Documentation/virt/kvm/locking.rst @@ -67,7 +67,7 @@ following two cases: 2. Write-Protection: The SPTE is present and the fault is caused by write-protect. That means we just need to change the W bit of the spte. -What we use to avoid all the race is the Host-writable bit and MMU-writable bit +What we use to avoid all the races is the Host-writable bit and MMU-writable bit on the spte: - Host-writable means the gfn is writable in the host kernel page tables and in @@ -130,7 +130,7 @@ to gfn. For indirect sp, we disabled fast page fault for simplicity. A solution for indirect sp could be to pin the gfn, for example via kvm_vcpu_gfn_to_pfn_atomic, before the cmpxchg. After the pinning: -- We have held the refcount of pfn that means the pfn can not be freed and +- We have held the refcount of pfn; that means the pfn can not be freed and be reused for another gfn. - The pfn is writable and therefore it cannot be shared between different gfns by KSM. @@ -186,22 +186,22 @@ writable between reading spte and updating spte. Like below case: The Dirty bit is lost in this case. In order to avoid this kind of issue, we always treat the spte as "volatile" -if it can be updated out of mmu-lock, see spte_has_volatile_bits(), it means, +if it can be updated out of mmu-lock [see spte_has_volatile_bits()]; it means the spte is always atomically updated in this case. 3) flush tlbs due to spte updated -If the spte is updated from writable to readonly, we should flush all TLBs, +If the spte is updated from writable to read-only, we should flush all TLBs, otherwise rmap_write_protect will find a read-only spte, even though the writable spte might be cached on a CPU's TLB. As mentioned before, the spte can be updated to writable out of mmu-lock on -fast page fault path, in order to easily audit the path, we see if TLBs need -be flushed caused by this reason in mmu_spte_update() since this is a common +fast page fault path. In order to easily audit the path, we see if TLBs needing +to be flushed caused this reason in mmu_spte_update() since this is a common function to update spte (present -> present). Since the spte is "volatile" if it can be updated out of mmu-lock, we always -atomically update the spte, the race caused by fast page fault can be avoided, +atomically update the spte and the race caused by fast page fault can be avoided. See the comments in spte_has_volatile_bits() and mmu_spte_update(). Lockless Access Tracking: @@ -283,9 +283,9 @@ time it will be set using the Dirty tracking mechanism described above. :Arch: x86 :Protects: wakeup_vcpus_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 + When VT-d posted-interrupts are 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 + 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/virt/kvm/ppc-pv.rst b/Documentation/virt/kvm/ppc-pv.rst index 5fdb907670be..740d03d25300 100644 --- a/Documentation/virt/kvm/ppc-pv.rst +++ b/Documentation/virt/kvm/ppc-pv.rst @@ -89,7 +89,7 @@ also define a new hypercall feature to indicate that the host can give you more registers. Only if the host supports the additional features, make use of them. The magic page layout is described by struct kvm_vcpu_arch_shared -in arch/powerpc/include/asm/kvm_para.h. +in arch/powerpc/include/uapi/asm/kvm_para.h. Magic page features =================== @@ -112,7 +112,7 @@ Magic page flags ================ In addition to features that indicate whether a host is capable of a particular -feature we also have a channel for a guest to tell the guest whether it's capable +feature we also have a channel for a guest to tell the host whether it's capable of something. This is what we call "flags". Flags are passed to the host in the low 12 bits of the Effective Address. @@ -139,7 +139,7 @@ Patched instructions ==================== The "ld" and "std" instructions are transformed to "lwz" and "stw" instructions -respectively on 32 bit systems with an added offset of 4 to accommodate for big +respectively on 32-bit systems with an added offset of 4 to accommodate for big endianness. The following is a list of mapping the Linux kernel performs when running as @@ -210,7 +210,7 @@ available on all targets. 2) PAPR hypercalls PAPR hypercalls are needed to run server PowerPC PAPR guests (-M pseries in QEMU). -These are the same hypercalls that pHyp, the POWER hypervisor implements. Some of +These are the same hypercalls that pHyp, the POWER hypervisor, implements. Some of them are handled in the kernel, some are handled in user space. This is only available on book3s_64. diff --git a/Documentation/virt/kvm/vcpu-requests.rst b/Documentation/virt/kvm/vcpu-requests.rst index 87f04c1fa53d..06718b9bc959 100644 --- a/Documentation/virt/kvm/vcpu-requests.rst +++ b/Documentation/virt/kvm/vcpu-requests.rst @@ -101,7 +101,7 @@ also be used, e.g. :: However, VCPU request users should refrain from doing so, as it would break the abstraction. The first 8 bits are reserved for architecture -independent requests, all additional bits are available for architecture +independent requests; all additional bits are available for architecture dependent requests. Architecture Independent Requests @@ -151,8 +151,8 @@ KVM_REQUEST_NO_WAKEUP This flag is applied to requests that only need immediate attention from VCPUs running in guest mode. That is, sleeping VCPUs do not need - to be awaken for these requests. Sleeping VCPUs will handle the - requests when they are awaken later for some other reason. + to be awakened for these requests. Sleeping VCPUs will handle the + requests when they are awakened later for some other reason. KVM_REQUEST_WAIT diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst index 487b6328b3e7..995780088eb2 100644 --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst @@ -57,7 +57,7 @@ information, see the SEV Key Management spec [api-spec]_ The main ioctl to access SEV is KVM_MEMORY_ENCRYPT_OP. If the argument to KVM_MEMORY_ENCRYPT_OP is NULL, the ioctl returns 0 if SEV is enabled -and ``ENOTTY` if it is disabled (on some older versions of Linux, +and ``ENOTTY`` if it is disabled (on some older versions of Linux, the ioctl runs normally even with a NULL argument, and therefore will likely return ``EFAULT``). If non-NULL, the argument to KVM_MEMORY_ENCRYPT_OP must be a struct kvm_sev_cmd:: diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst index 8364afa228ec..26f62034b6f3 100644 --- a/Documentation/virt/kvm/x86/mmu.rst +++ b/Documentation/virt/kvm/x86/mmu.rst @@ -205,7 +205,7 @@ Shadow pages contain the following information: role.passthrough: The page is not backed by a guest page table, but its first entry points to one. This is set if NPT uses 5-level page tables (host - CR4.LA57=1) and is shadowing L1's 4-level NPT (L1 CR4.LA57=1). + CR4.LA57=1) and is shadowing L1's 4-level NPT (L1 CR4.LA57=0). gfn: Either the guest page table containing the translations shadowed by this page, or the base page frame for linear translations. See role.direct. diff --git a/Documentation/virt/paravirt_ops.rst b/Documentation/virt/paravirt_ops.rst index 6b789d27cead..62d867e0d4d6 100644 --- a/Documentation/virt/paravirt_ops.rst +++ b/Documentation/virt/paravirt_ops.rst @@ -5,31 +5,31 @@ Paravirt_ops ============ Linux provides support for different hypervisor virtualization technologies. -Historically different binary kernels would be required in order to support -different hypervisors, this restriction was removed with pv_ops. +Historically, different binary kernels would be required in order to support +different hypervisors; this restriction was removed with pv_ops. Linux pv_ops is a virtualization API which enables support for different hypervisors. It allows each hypervisor to override critical operations and allows a single kernel binary to run on all supported execution environments including native machine -- without any hypervisors. pv_ops provides a set of function pointers which represent operations -corresponding to low level critical instructions and high level -functionalities in various areas. pv-ops allows for optimizations at run -time by enabling binary patching of the low-ops critical operations +corresponding to low-level critical instructions and high-level +functionalities in various areas. pv_ops allows for optimizations at run +time by enabling binary patching of the low-level critical operations at boot time. pv_ops operations are classified into three categories: - simple indirect call - These operations correspond to high level functionality where it is + These operations correspond to high-level functionality where it is known that the overhead of indirect call isn't very important. - indirect call which allows optimization with binary patch - Usually these operations correspond to low level critical instructions. They + Usually these operations correspond to low-level critical instructions. They are called frequently and are performance critical. The overhead is very important. - a set of macros for hand written assembly code Hand written assembly codes (.S files) also need paravirtualization - because they include sensitive instructions or some of code paths in + because they include sensitive instructions or some code paths in them are very performance critical. |