- 12 Jul, 2011 40 commits
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Nadav Har'El authored
This patch includes a brief introduction to the nested vmx feature in the Documentation/kvm directory. The document also includes a copy of the vmcs12 structure, as requested by Avi Kivity. [marcelo: move to Documentation/virtual/kvm] Signed-off-by:
Nadav Har'El <nyh@il.ibm.com> Signed-off-by:
Marcelo Tosatti <mtosatti@redhat.com>
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Nadav Har'El authored
Small corrections of KVM (spelling, etc.) not directly related to nested VMX. Signed-off-by:
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Nadav Har'El authored
If the "nested" module option is enabled, add the "VMX" CPU feature to the list of CPU features KVM advertises with the KVM_GET_SUPPORTED_CPUID ioctl. Qemu uses this ioctl, and intersects KVM's list with its own list of desired cpu features (depending on the -cpu option given to qemu) to determine the final list of features presented to the guest. Signed-off-by:
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Nadav Har'El authored
In the unlikely case that L1 does not capture MSR_IA32_TSC, L0 needs to emulate this MSR write by L2 by modifying vmcs02.tsc_offset. We also need to set vmcs12.tsc_offset, for this change to survive the next nested entry (see prepare_vmcs02()). Additionally, we also need to modify vmx_adjust_tsc_offset: The semantics of this function is that the TSC of all guests on this vcpu, L1 and possibly several L2s, need to be adjusted. To do this, we need to adjust vmcs01's tsc_offset (this offset will also apply to each L2s we enter). We can't set vmcs01 now, so we have to remember this adjustment and apply it when we later exit to L1. Signed-off-by:
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Nadav Har'El authored
KVM's "Lazy FPU loading" means that sometimes L0 needs to set CR0.TS, even if a guest didn't set it. Moreover, L0 must also trap CR0.TS changes and NM exceptions, even if we have a guest hypervisor (L1) who didn't want these traps. And of course, conversely: If L1 wanted to trap these events, we must let it, even if L0 is not interested in them. This patch fixes some existing KVM code (in update_exception_bitmap(), vmx_fpu_activate(), vmx_fpu_deactivate()) to do the correct merging of L0's and L1's needs. Note that handle_cr() was already fixed in the above patch, and that new code in introduced in previous patches already handles CR0 correctly (see prepare_vmcs02(), prepare_vmcs12(), and nested_vmx_vmexit()). Signed-off-by:
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Nadav Har'El authored
When L2 tries to modify CR0 or CR4 (with mov or clts), and modifies a bit which L1 asked to shadow (via CR[04]_GUEST_HOST_MASK), we already do the right thing: we let L1 handle the trap (see nested_vmx_exit_handled_cr() in a previous patch). When L2 modifies bits that L1 doesn't care about, we let it think (via CR[04]_READ_SHADOW) that it did these modifications, while only changing (in GUEST_CR[04]) the bits that L0 doesn't shadow. This is needed for corect handling of CR0.TS for lazy FPU loading: L0 may want to leave TS on, while pretending to allow the guest to change it. Signed-off-by:
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Nadav Har'El authored
This patch adds correct handling of IDT_VECTORING_INFO_FIELD for the nested case. When a guest exits while delivering an interrupt or exception, we get this information in IDT_VECTORING_INFO_FIELD in the VMCS. When L2 exits to L1, there's nothing we need to do, because L1 will see this field in vmcs12, and handle it itself. However, when L2 exits and L0 handles the exit itself and plans to return to L2, L0 must inject this event to L2. In the normal non-nested case, the idt_vectoring_info case is discovered after the exit, and the decision to inject (though not the injection itself) is made at that point. However, in the nested case a decision of whether to return to L2 or L1 also happens during the injection phase (see the previous patches), so in the nested case we can only decide what to do about the idt_vectoring_info right after the injection, i.e., in the beginning of vmx_vcpu_run, which is the first time we know for sure if we're staying in L2. Therefore, when we exit L2 (is_guest_mode(vcpu)), we disable the regular vmx_complete_interrupts() code which queues the idt_vectoring_info for injection on next entry - because such injection would not be appropriate if we will decide to exit to L1. Rather, we just save the idt_vectoring_info and related fields in vmcs12 (which is a convenient place to save these fields). On the next entry in vmx_vcpu_run (*after* the injection phase, potentially exiting to L1 to inject an event requested by user space), if we find ourselves in L1 we don't need to do anything with those values we saved (as explained above). But if we find that we're in L2, or rather *still* at L2 (it's not nested_run_pending, meaning that this is the first round of L2 running after L1 having just launched it), we need to inject the event saved in those fields - by writing the appropriate VMCS fields. Signed-off-by:
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Nadav Har'El authored
Similar to the previous patch, but concerning injection of exceptions rather than external interrupts. Signed-off-by:
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Nadav Har'El authored
The code in this patch correctly emulates external-interrupt injection while a nested guest L2 is running. Because of this code's relative un-obviousness, I include here a longer-than- usual justification for what it does - much longer than the code itself ;-) To understand how to correctly emulate interrupt injection while L2 is running, let's look first at what we need to emulate: How would things look like if the extra L0 hypervisor layer is removed, and instead of L0 injecting an interrupt, we had hardware delivering an interrupt? Now we have L1 running on bare metal with a guest L2, and the hardware generates an interrupt. Assuming that L1 set PIN_BASED_EXT_INTR_MASK to 1, and VM_EXIT_ACK_INTR_ON_EXIT to 0 (we'll revisit these assumptions below), what happens now is this: The processor exits from L2 to L1, with an external- interrupt exit reason but without an interrupt vector. L1 runs, with interrupts disabled, and it doesn't yet know what the interrupt was. Soon after, it enables interrupts and only at that moment, it gets the interrupt from the processor. when L1 is KVM, Linux handles this interrupt. Now we need exactly the same thing to happen when that L1->L2 system runs on top of L0, instead of real hardware. This is how we do this: When L0 wants to inject an interrupt, it needs to exit from L2 to L1, with external-interrupt exit reason (with an invalid interrupt vector), and run L1. Just like in the bare metal case, it likely can't deliver the interrupt to L1 now because L1 is running with interrupts disabled, in which case it turns on the interrupt window when running L1 after the exit. L1 will soon enable interrupts, and at that point L0 will gain control again and inject the interrupt to L1. Finally, there is an extra complication in the code: when nested_run_pending, we cannot return to L1 now, and must launch L2. We need to remember the interrupt we wanted to inject (and not clear it now), and do it on the next exit. The above explanation shows that the relative strangeness of the nested interrupt injection code in this patch, and the extra interrupt-window exit incurred, are in fact necessary for accurate emulation, and are not just an unoptimized implementation. Let's revisit now the two assumptions made above: If L1 turns off PIN_BASED_EXT_INTR_MASK (no hypervisor that I know does, by the way), things are simple: L0 may inject the interrupt directly to the L2 guest - using the normal code path that injects to any guest. We support this case in the code below. If L1 turns on VM_EXIT_ACK_INTR_ON_EXIT, things look very different from the description above: L1 expects to see an exit from L2 with the interrupt vector already filled in the exit information, and does not expect to be interrupted again with this interrupt. The current code does not (yet) support this case, so we do not allow the VM_EXIT_ACK_INTR_ON_EXIT exit-control to be turned on by L1. Signed-off-by:
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Nadav Har'El authored
This patch contains the logic of whether an L2 exit should be handled by L0 and then L2 should be resumed, or whether L1 should be run to handle this exit (using the nested_vmx_vmexit() function of the previous patch). The basic idea is to let L1 handle the exit only if it actually asked to trap this sort of event. For example, when L2 exits on a change to CR0, we check L1's CR0_GUEST_HOST_MASK to see if L1 expressed interest in any bit which changed; If it did, we exit to L1. But if it didn't it means that it is we (L0) that wished to trap this event, so we handle it ourselves. The next two patches add additional logic of what to do when an interrupt or exception is injected: Does L0 need to do it, should we exit to L1 to do it, or should we resume L2 and keep the exception to be injected later. We keep a new flag, "nested_run_pending", which can override the decision of which should run next, L1 or L2. nested_run_pending=1 means that we *must* run L2 next, not L1. This is necessary in particular when L1 did a VMLAUNCH of L2 and therefore expects L2 to be run (and perhaps be injected with an event it specified, etc.). Nested_run_pending is especially intended to avoid switching to L1 in the injection decision-point described above. Signed-off-by:
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Nadav Har'El authored
This patch adds a bunch of tests of the validity of the vmcs12 fields, according to what the VMX spec and our implementation allows. If fields we cannot (or don't want to) honor are discovered, an entry failure is emulated. According to the spec, there are two types of entry failures: If the problem was in vmcs12's host state or control fields, the VMLAUNCH instruction simply fails. But a problem is found in the guest state, the behavior is more similar to that of an exit. Signed-off-by:
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Nadav Har'El authored
This patch implements nested_vmx_vmexit(), called when the nested L2 guest exits and we want to run its L1 parent and let it handle this exit. Note that this will not necessarily be called on every L2 exit. L0 may decide to handle a particular exit on its own, without L1's involvement; In that case, L0 will handle the exit, and resume running L2, without running L1 and without calling nested_vmx_vmexit(). The logic for deciding whether to handle a particular exit in L1 or in L0, i.e., whether to call nested_vmx_vmexit(), will appear in a separate patch below. Signed-off-by:
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Nadav Har'El authored
Before nested VMX support, the exit handler for a guest executing a VMX instruction (vmclear, vmlaunch, vmptrld, vmptrst, vmread, vmread, vmresume, vmwrite, vmon, vmoff), was handle_vmx_insn(). This handler simply threw a #UD exception. Now that all these exit reasons are properly handled (and emulate the respective VMX instruction), nothing calls this dummy handler and it can be removed. Signed-off-by:
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Nadav Har'El authored
Implement the VMLAUNCH and VMRESUME instructions, allowing a guest hypervisor to run its own guests. This patch does not include some of the necessary validity checks on vmcs12 fields before the entry. These will appear in a separate patch below. Signed-off-by:
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Nadav Har'El authored
This patch contains code to prepare the VMCS which can be used to actually run the L2 guest, vmcs02. prepare_vmcs02 appropriately merges the information in vmcs12 (the vmcs that L1 built for L2) and in vmcs01 (our desires for our own guests). Signed-off-by:
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Nadav Har'El authored
Move some of the control field setup to common functions. These functions will also be needed for running L2 guests - L0's desires (expressed in these functions) will be appropriately merged with L1's desires. Signed-off-by:
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Nadav Har'El authored
Move the setting of constant host-state fields (fields that do not change throughout the life of the guest) from vmx_vcpu_setup to a new common function vmx_set_constant_host_state(). This function will also be used to set the host state when running L2 guests. Signed-off-by:
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Nadav Har'El authored
Implement the VMREAD and VMWRITE instructions. With these instructions, L1 can read and write to the VMCS it is holding. The values are read or written to the fields of the vmcs12 structure introduced in a previous patch. Signed-off-by:
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Nadav Har'El authored
This patch implements the VMPTRST instruction. Signed-off-by:
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Nadav Har'El authored
This patch implements the VMPTRLD instruction. Signed-off-by:
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Nadav Har'El authored
This patch implements the VMCLEAR instruction. Signed-off-by:
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Nadav Har'El authored
VMX instructions specify success or failure by setting certain RFLAGS bits. This patch contains common functions to do this, and they will be used in the following patches which emulate the various VMX instructions. Signed-off-by:
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Nadav Har'El authored
In this patch we add to vmcs12 (the VMCS that L1 keeps for L2) all the standard VMCS fields. Later patches will enable L1 to read and write these fields using VMREAD/ VMWRITE, and they will be used during a VMLAUNCH/VMRESUME in preparing vmcs02, a hardware VMCS for running L2. Signed-off-by:
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Nadav Har'El authored
We saw in a previous patch that L1 controls its L2 guest with a vcms12. L0 needs to create a real VMCS for running L2. We call that "vmcs02". A later patch will contain the code, prepare_vmcs02(), for filling the vmcs02 fields. This patch only contains code for allocating vmcs02. In this version, prepare_vmcs02() sets *all* of vmcs02's fields each time we enter from L1 to L2, so keeping just one vmcs02 for the vcpu is enough: It can be reused even when L1 runs multiple L2 guests. However, in future versions we'll probably want to add an optimization where vmcs02 fields that rarely change will not be set each time. For that, we may want to keep around several vmcs02s of L2 guests that have recently run, so that potentially we could run these L2s again more quickly because less vmwrites to vmcs02 will be needed. This patch adds to each vcpu a vmcs02 pool, vmx->nested.vmcs02_pool, which remembers the vmcs02s last used to run up to VMCS02_POOL_SIZE L2s. As explained above, in the current version we choose VMCS02_POOL_SIZE=1, I.e., one vmcs02 is allocated (and loaded onto the processor), and it is reused to enter any L2 guest. In the future, when prepare_vmcs02() is optimized not to set all fields every time, VMCS02_POOL_SIZE should be increased. Signed-off-by:
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Nadav Har'El authored
This patch includes a utility function for decoding pointer operands of VMX instructions issued by L1 (a guest hypervisor) Signed-off-by:
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Nadav Har'El authored
When the guest can use VMX instructions (when the "nested" module option is on), it should also be able to read and write VMX MSRs, e.g., to query about VMX capabilities. This patch adds this support. Signed-off-by:
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Nadav Har'El authored
An implementation of VMX needs to define a VMCS structure. This structure is kept in guest memory, but is opaque to the guest (who can only read or write it with VMX instructions). This patch starts to define the VMCS structure which our nested VMX implementation will present to L1. We call it "vmcs12", as it is the VMCS that L1 keeps for its L2 guest. We will add more content to this structure in later patches. This patch also adds the notion (as required by the VMX spec) of L1's "current VMCS", and finally includes utility functions for mapping the guest-allocated VMCSs in host memory. Signed-off-by:
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Nadav Har'El authored
This patch allows the guest to enable the VMXE bit in CR4, which is a prerequisite to running VMXON. Whether to allow setting the VMXE bit now depends on the architecture (svm or vmx), so its checking has moved to kvm_x86_ops->set_cr4(). This function now returns an int: If kvm_x86_ops->set_cr4() returns 1, __kvm_set_cr4() will also return 1, and this will cause kvm_set_cr4() will throw a #GP. Turning on the VMXE bit is allowed only when the nested VMX feature is enabled, and turning it off is forbidden after a vmxon. Signed-off-by:
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Nadav Har'El authored
This patch allows a guest to use the VMXON and VMXOFF instructions, and emulates them accordingly. Basically this amounts to checking some prerequisites, and then remembering whether the guest has enabled or disabled VMX operation. Signed-off-by:
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Nadav Har'El authored
This patch adds to kvm_intel a module option "nested". This option controls whether the guest can use VMX instructions, i.e., whether we allow nested virtualization. A similar, but separate, option already exists for the SVM module. This option currently defaults to 0, meaning that nested VMX must be explicitly enabled by giving nested=1. When nested VMX matures, the default should probably be changed to enable nested VMX by default - just like nested SVM is currently enabled by default. Signed-off-by:
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Takuya Yoshikawa authored
During tracing the emulator, we noticed that init_emulate_ctxt() sometimes took a bit longer time than we expected. This patch is for mitigating the problem by some degree. By looking into the function, we soon notice that it clears the whole decode_cache whose size is about 2.5K bytes now. Furthermore, most of the bytes are taken for the two read_cache arrays, which are used only by a few instructions. Considering the fact that we are not assuming the cache arrays have been cleared when we store actual data, we do not need to clear the arrays: 2K bytes elimination. In addition, we can avoid clearing the fetch_cache and regs arrays. This patch changes the initialization not to clear the arrays. On our 64-bit host, init_emulate_ctxt() becomes 0.3 to 0.5us faster with this patch applied. Signed-off-by:
Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> Cc: Gleb Natapov <gleb@redhat.com> Signed-off-by:
Avi Kivity <avi@redhat.com>
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Takuya Yoshikawa authored
Use a local pointer to the emulate_ctxt for simplicity. Then, arrange the hard-to-read mode selection lines neatly. Signed-off-by:
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Jan Kiszka authored
So far kvm_arch_vcpu_setup is responsible for freeing the vcpu struct if it fails. Move this confusing resonsibility back into the hands of kvm_vm_ioctl_create_vcpu. Only kvm_arch_vcpu_setup of x86 is affected, all other archs cannot fail. Signed-off-by:
Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by:
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Nadav Har'El authored
In VMX, before we bring down a CPU we must VMCLEAR all VMCSs loaded on it because (at least in theory) the processor might not have written all of its content back to memory. Since a patch from June 26, 2008, this is done using a per-cpu "vcpus_on_cpu" linked list of vcpus loaded on each CPU. The problem is that with nested VMX, we no longer have the concept of a vcpu being loaded on a cpu: A vcpu has multiple VMCSs (one for L1, a pool for L2s), and each of those may be have been last loaded on a different cpu. So instead of linking the vcpus, we link the VMCSs, using a new structure loaded_vmcs. This structure contains the VMCS, and the information pertaining to its loading on a specific cpu (namely, the cpu number, and whether it was already launched on this cpu once). In nested we will also use the same structure to hold L2 VMCSs, and vmx->loaded_vmcs is a pointer to the currently active VMCS. Signed-off-by:
Acked-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by:
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Avi Kivity authored
Instead of blacklisting known-unsupported cpuid leaves, whitelist known- supported leaves. This is more conservative and prevents us from reporting features we don't support. Also whitelist a few more leaves while at it. Signed-off-by:
Joerg Roedel <joerg.roedel@amd.com> Signed-off-by:
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Xiao Guangrong authored
Introduce drop_parent_pte to remove the rmap of parent pte and clear parent pte Signed-off-by:
Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> Signed-off-by:
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Xiao Guangrong authored
Cleanup the same operation between kvm_mmu_page_unlink_children and mmu_pte_write_zap_pte Signed-off-by:
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Xiao Guangrong authored
Parent pte rmap and page rmap are very similar, so use the same arithmetic for them Signed-off-by:
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Xiao Guangrong authored
Abstract the operation of rmap to spte_list, then we can use it for the reverse mapping of parent pte in the later patch Signed-off-by:
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Xiao Guangrong authored
Fix: warning: ‘cs_sel’ may be used uninitialized in this function warning: ‘ss_sel’ may be used uninitialized in this function Signed-off-by:
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