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2013-04-22KVM: nVMX: VM_ENTRY/EXIT_LOAD_IA32_EFER overrides EFER.LMA settingsJan Kiszka
If we load the complete EFER MSR on entry or exit, EFER.LMA (and LME) loading is skipped. Their consistency is already checked now before starting the transition. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Validate EFER values for VM_ENTRY/EXIT_LOAD_IA32_EFERJan Kiszka
As we may emulate the loading of EFER on VM-entry and VM-exit, implement the checks that VMX performs on the guest and host values on vmlaunch/ vmresume. Factor out kvm_valid_efer for this purpose which checks for set reserved bits. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Fix conditions for NMI injectionJan Kiszka
The logic for checking if interrupts can be injected has to be applied also on NMIs. The difference is that if NMI interception is on these events are consumed and blocked by the VM exit. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: VMX: Move vmx_nmi_allowed after vmx_set_nmi_maskJan Kiszka
vmx_set_nmi_mask will soon be used by vmx_nmi_allowed. No functional changes. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: x86: Fix memory leak in vmx.cAndrew Honig
If userspace creates and destroys multiple VMs within the same process we leak 20k of memory in the userspace process context per VM. This patch frees the memory in kvm_arch_destroy_vm. If the process exits without closing the VM file descriptor or the file descriptor has been shared with another process then we don't free the memory. It's still possible for a user space process to leak memory if the last process to close the fd for the VM is not the process that created it. However, this is an unexpected case that's only caused by a user space process that's misbehaving. Signed-off-by: Andrew Honig <ahonig@google.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: x86: fix error return code in kvm_arch_vcpu_init()Wei Yongjun
Fix to return a negative error code from the error handling case instead of 0, as returned elsewhere in this function. Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Enable and disable shadow vmcs functionalityAbel Gordon
Once L1 loads VMCS12 we enable shadow-vmcs capability and copy all the VMCS12 shadowed fields to the shadow vmcs. When we release the VMCS12, we also disable shadow-vmcs capability. Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Synchronize VMCS12 content with the shadow vmcsAbel Gordon
Synchronize between the VMCS12 software controlled structure and the processor-specific shadow vmcs Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Copy VMCS12 to processor-specific shadow vmcsAbel Gordon
Introduce a function used to copy fields from the software controlled VMCS12 to the processor-specific shadow vmcs Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Copy processor-specific shadow-vmcs to VMCS12Abel Gordon
Introduce a function used to copy fields from the processor-specific shadow vmcs to the software controlled VMCS12 Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Release shadow vmcsAbel Gordon
Unmap vmcs12 and release the corresponding shadow vmcs Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Allocate shadow vmcsAbel Gordon
Allocate a shadow vmcs used by the processor to shadow part of the fields stored in the software defined VMCS12 (let L1 access fields without causing exits). Note we keep a shadow vmcs only for the current vmcs12. Once a vmcs12 becomes non-current, its shadow vmcs is released. Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Fix VMXON emulationAbel Gordon
handle_vmon doesn't check if L1 is already in root mode (VMXON was previously called). This patch adds this missing check and calls nested_vmx_failValid if VMX is already ON. We need this check because L0 will allocate the shadow vmcs when L1 executes VMXON and we want to avoid host leaks (due to shadow vmcs allocation) if L1 executes VMXON repeatedly. Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Refactor handle_vmwriteAbel Gordon
Refactor existent code so we re-use vmcs12_write_any to copy fields from the shadow vmcs specified by the link pointer (used by the processor, implementation-specific) to the VMCS12 software format used by L0 to hold the fields in L1 memory address space. Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Introduce vmread and vmwrite bitmapsAbel Gordon
Prepare vmread and vmwrite bitmaps according to a pre-specified list of fields. These lists are intended to specifiy most frequent accessed fields so we can minimize the number of fields that are copied from/to the software controlled VMCS12 format to/from to processor-specific shadow vmcs. The lists were built measuring the VMCS fields access rate after L2 Ubuntu 12.04 booted when it was running on top of L1 KVM, also Ubuntu 12.04. Note that during boot there were additional fields which were frequently modified but they were not added to these lists because after boot these fields were not longer accessed by L1. Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-22KVM: nVMX: Detect shadow-vmcs capabilityAbel Gordon
Add logic required to detect if shadow-vmcs is supported by the processor. Introduce a new kernel module parameter to specify if L0 should use shadow vmcs (or not) to run L1. Signed-off-by: Abel Gordon <abelg@il.ibm.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-17KVM: x86: Fix posted interrupt with CONFIG_SMP=nZhang, Yang Z
->send_IPI_mask is not defined on UP. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: VMX: Fix check guest state validity if a guest is in VM86 modeGleb Natapov
If guest vcpu is in VM86 mode the vcpu state should be checked as if in real mode. Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: nVMX: check vmcs12 for valid activity statePaolo Bonzini
KVM does not use the activity state VMCS field, and does not support it in nested VMX either (the corresponding bits in the misc VMX feature MSR are zero). Fail entry if the activity state is set to anything but "active". Since the value will always be the same for L1 and L2, we do not need to read and write the corresponding VMCS field on L1/L2 transitions, either. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: VMX: Use posted interrupt to deliver virtual interruptYang Zhang
If posted interrupt is avaliable, then uses it to inject virtual interrupt to guest. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: VMX: Add the deliver posted interrupt algorithmYang Zhang
Only deliver the posted interrupt when target vcpu is running and there is no previous interrupt pending in pir. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: Set TMR when programming ioapic entryYang Zhang
We already know the trigger mode of a given interrupt when programming the ioapice entry. So it's not necessary to set it in each interrupt delivery. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: Call common update function when ioapic entry changed.Yang Zhang
Both TMR and EOI exit bitmap need to be updated when ioapic changed or vcpu's id/ldr/dfr changed. So use common function instead eoi exit bitmap specific function. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: VMX: Check the posted interrupt capabilityYang Zhang
Detect the posted interrupt feature. If it exists, then set it in vmcs_config. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-16KVM: VMX: Enable acknowledge interupt on vmexitYang Zhang
The "acknowledge interrupt on exit" feature controls processor behavior for external interrupt acknowledgement. When this control is set, the processor acknowledges the interrupt controller to acquire the interrupt vector on VM exit. After enabling this feature, an interrupt which arrived when target cpu is running in vmx non-root mode will be handled by vmx handler instead of handler in idt. Currently, vmx handler only fakes an interrupt stack and jump to idt table to let real handler to handle it. Further, we will recognize the interrupt and only delivery the interrupt which not belong to current vcpu through idt table. The interrupt which belonged to current vcpu will be handled inside vmx handler. This will reduce the interrupt handle cost of KVM. Also, interrupt enable logic is changed if this feature is turnning on: Before this patch, hypervior call local_irq_enable() to enable it directly. Now IF bit is set on interrupt stack frame, and will be enabled on a return from interrupt handler if exterrupt interrupt exists. If no external interrupt, still call local_irq_enable() to enable it. Refer to Intel SDM volum 3, chapter 33.2. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-15KVM: Let ioapic know the irq line statusYang Zhang
Userspace may deliver RTC interrupt without query the status. So we want to track RTC EOI for this case. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-15KVM: Add reset/restore rtc_status supportYang Zhang
restore rtc_status from migration or save/restore Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-15KVM: Return destination vcpu on interrupt injectionYang Zhang
Add a new parameter to know vcpus who received the interrupt. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-15KVM: Add vcpu info to ioapic_update_eoi()Yang Zhang
Add vcpu info to ioapic_update_eoi, so we can know which vcpu issued this EOI. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-04-14KVM: nVMX: Avoid reading VM_EXIT_INTR_ERROR_CODE needlessly on nested exitsJan Kiszka
We only need to update vm_exit_intr_error_code if there is a valid exit interruption information and it comes with a valid error code. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-14KVM: nVMX: Fix conditions for interrupt injectionJan Kiszka
If we are entering guest mode, we do not want L0 to interrupt this vmentry with all its side effects on the vmcs. Therefore, injection shall be disallowed during L1->L2 transitions, as in the previous version. However, this check is conceptually independent of nested_exit_on_intr, so decouple it. If L1 traps external interrupts, we can kick the guest from L2 to L1, also just like the previous code worked. But we no longer need to consider L1's idt_vectoring_info_field. It will always be empty at this point. Instead, if L2 has pending events, those are now found in the architectural queues and will, thus, prevent vmx_interrupt_allowed from being called at all. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-14KVM: nVMX: Rework event injection and recoveryJan Kiszka
The basic idea is to always transfer the pending event injection on vmexit into the architectural state of the VCPU and then drop it from there if it turns out that we left L2 to enter L1, i.e. if we enter prepare_vmcs12. vmcs12_save_pending_events takes care to transfer pending L0 events into the queue of L1. That is mandatory as L1 may decide to switch the guest state completely, invalidating or preserving the pending events for later injection (including on a different node, once we support migration). This concept is based on the rule that a pending vmlaunch/vmresume is not canceled. Otherwise, we would risk to lose injected events or leak them into the wrong queues. Encode this rule via a WARN_ON_ONCE at the entry of nested_vmx_vmexit. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-14KVM: nVMX: Fix injection of PENDING_INTERRUPT and NMI_WINDOW exits to L1Jan Kiszka
Check if the interrupt or NMI window exit is for L1 by testing if it has the corresponding controls enabled. This is required when we allow direct injection from L0 to L2 Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-14KVM: emulator: mark 0xff 0x7d opcode as undefined.Gleb Natapov
Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-14KVM: emulator: Do not fail on emulation of undefined opcodeGleb Natapov
Emulation of undefined opcode should inject #UD instead of causing emulation failure. Do that by moving Undefined flag check to emulation stage and injection #UD there. Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-14KVM: VMX: do not try to reexecute failed instruction while emulating invalid ↵Gleb Natapov
guest state During invalid guest state emulation vcpu cannot enter guest mode to try to reexecute instruction that emulator failed to emulate, so emulation will happen again and again. Prevent that by telling the emulator that instruction reexecution should not be attempted. Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-14KVM: emulator: fix unimplemented instruction detectionGleb Natapov
Unimplemented instruction detection is broken for group instructions since it relies on "flags" field of opcode to be zero, but all instructions in a group inherit flags from a group encoding. Fix that by having a separate flag for unimplemented instructions. Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-11x86, xen, gdt: Remove the pvops variant of store_gdt.Konrad Rzeszutek Wilk
The two use-cases where we needed to store the GDT were during ACPI S3 suspend and resume. As the patches: x86/gdt/i386: store/load GDT for ACPI S3 or hibernation/resume path is not needed x86/gdt/64-bit: store/load GDT for ACPI S3 or hibernate/resume path is not needed. have demonstrated - there are other mechanism by which the GDT is saved and reloaded during early resume path. Hence we do not need to worry about the pvops call-chain for saving the GDT and can and can eliminate it. The other areas where the store_gdt is used are never going to be hit when running under the pvops platforms. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Link: http://lkml.kernel.org/r/1365194544-14648-4-git-send-email-konrad.wilk@oracle.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2013-04-11KVM: x86 emulator: Fix segment loading in VM86Kevin Wolf
This fixes a regression introduced in commit 03ebebeb1 ("KVM: x86 emulator: Leave segment limit and attributs alone in real mode"). The mentioned commit changed the segment descriptors for both real mode and VM86 to only update the segment base instead of creating a completely new descriptor with limit 0xffff so that unreal mode keeps working across a segment register reload. This leads to an invalid segment descriptor in the eyes of VMX, which seems to be okay for real mode because KVM will fix it up before the next VM entry or emulate the state, but it doesn't do this if the guest is in VM86, so we end up with: KVM: entry failed, hardware error 0x80000021 Fix this by effectively reverting commit 03ebebeb1 for VM86 and leaving it only in place for real mode, which is where it's really needed. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-08KVM: Move kvm_spurious_fault to x86.cGeoff Levand
The routine kvm_spurious_fault() is an x86 specific routine, so move it from virt/kvm/kvm_main.c to arch/x86/kvm/x86.c. Fixes this sparse warning when building on arm64: virt/kvm/kvm_main.c:warning: symbol 'kvm_spurious_fault' was not declared. Should it be static? Signed-off-by: Geoff Levand <geoff@infradead.org> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-08KVM: VMX: Add missing braces to avoid redundant error checkJan Kiszka
The code was already properly aligned, now also add the braces to avoid that err is checked even if alloc_apic_access_page didn't run and change it. Found via Coccinelle by Fengguang Wu. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-08KVM: x86: fix memory leak in vmx_initYang Zhang
Free vmx_msr_bitmap_longmode_x2apic and vmx_msr_bitmap_longmode if kvm_init() fails. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-07KVM: nVMX: Check exit control for VM_EXIT_SAVE_IA32_PAT, not entry controlsJan Kiszka
Obviously a copy&paste mistake: prepare_vmcs12 has to check L1's exit controls for VM_EXIT_SAVE_IA32_PAT. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-07KVM: Call kvm_apic_match_dest() to check destination vcpuYang Zhang
For a given vcpu, kvm_apic_match_dest() will tell you whether the vcpu in the destination list quickly. Drop kvm_calculate_eoi_exitmap() and use kvm_apic_match_dest() instead. Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-07Revert "KVM: MMU: Move kvm_mmu_free_some_pages() into kvm_mmu_alloc_page()"Takuya Yoshikawa
With the following commit, shadow pages can be zapped at random during a shadow page talbe walk: KVM: MMU: Move kvm_mmu_free_some_pages() into kvm_mmu_alloc_page() 7ddca7e43c8f28f9419da81a0e7730b66aa60fe9 This patch reverts it and fixes __direct_map() and FNAME(fetch)(). Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-07KVM: Allow cross page reads and writes from cached translations.Andrew Honig
This patch adds support for kvm_gfn_to_hva_cache_init functions for reads and writes that will cross a page. If the range falls within the same memslot, then this will be a fast operation. If the range is split between two memslots, then the slower kvm_read_guest and kvm_write_guest are used. Tested: Test against kvm_clock unit tests. Signed-off-by: Andrew Honig <ahonig@google.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-02x86, cpu: Convert AMD Erratum 383Borislav Petkov
Convert the AMD erratum 383 testing code to the bug infrastructure. This allows keeping the AMD-specific erratum testing machinery private to amd.c and not export symbols to modules needlessly. Signed-off-by: Borislav Petkov <bp@suse.de> Link: http://lkml.kernel.org/r/1363788448-31325-6-git-send-email-bp@alien8.de Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2013-04-02pmu: prepare for migration supportPaolo Bonzini
In order to migrate the PMU state correctly, we need to restore the values of MSR_CORE_PERF_GLOBAL_STATUS (a read-only register) and MSR_CORE_PERF_GLOBAL_OVF_CTRL (which has side effects when written). We also need to write the full 40-bit value of the performance counter, which would only be possible with a v3 architectural PMU's full-width counter MSRs. To distinguish host-initiated writes from the guest's, pass the full struct msr_data to kvm_pmu_set_msr. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-03-21KVM: MMU: Rename kvm_mmu_free_some_pages() to make_mmu_pages_available()Takuya Yoshikawa
The current name "kvm_mmu_free_some_pages" should be used for something that actually frees some shadow pages, as we expect from the name, but what the function is doing is to make some, KVM_MIN_FREE_MMU_PAGES, shadow pages available: it does nothing when there are enough. This patch changes the name to reflect this meaning better; while doing this renaming, the code in the wrapper function is inlined into the main body since the whole function will be inlined into the only caller now. Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-03-21KVM: MMU: Move kvm_mmu_free_some_pages() into kvm_mmu_alloc_page()Takuya Yoshikawa
What this function is doing is to ensure that the number of shadow pages does not exceed the maximum limit stored in n_max_mmu_pages: so this is placed at every code path that can reach kvm_mmu_alloc_page(). Although it might have some sense to spread this function in each such code path when it could be called before taking mmu_lock, the rule was changed not to do so. Taking this background into account, this patch moves it into kvm_mmu_alloc_page() and simplifies the code. Note: the unlikely hint in kvm_mmu_free_some_pages() guarantees that the overhead of this function is almost zero except when we actually need to allocate some shadow pages, so we do not need to care about calling it multiple times in one path by doing kvm_mmu_get_page() a few times. Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>