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| From 28e67537895c4b46b9721f19609ee4f2ccb8c132 Mon Sep 17 00:00:00 2001 | |
| From: pi <secret@hidden.mail> | |
| Date: Sat, 7 Nov 2020 18:41:42 +0100 | |
| Subject: [PATCH] Add 'hide-hypervisor' QMP command | |
| CAUTION: Extremely hacky stuff below. Use at own risk of bugs, breakage and | |
| bear attacks. | |
| Introduce a new QMP call to disable the hypervisor CPUID flag at runtime on | |
| x86 KVM. Allows the guest OS to initialize with full hypervisor/PV support | |
| while allowing broken guest applications that require a bare metal machine | |
| to function. Enable 'hypervisor' flag on boot command, then wait for guest | |
| boot, then run 'hide-hypervisor' via QMP. Might break guests that depend on | |
| CPUID never changing at runtime, as is the case on real hardware (excluding | |
| microcode updates, which are magic anyway). | |
| --- | |
| hw/core/machine-qmp-cmds.c | 38 ++++++++++++++++++++++++++++++++++++++ | |
| qapi/machine.json | 9 +++++++++ | |
| target/i386/cpu.h | 4 ++++ | |
| target/i386/kvm.c | 6 ++++-- | |
| 4 files changed, 55 insertions(+), 2 deletions(-) | |
| diff --git a/hw/core/machine-qmp-cmds.c b/hw/core/machine-qmp-cmds.c | |
| index 963088b798..6c571a5af1 100644 | |
| --- a/hw/core/machine-qmp-cmds.c | |
| +++ b/hw/core/machine-qmp-cmds.c | |
| @@ -23,6 +23,44 @@ | |
| #include "sysemu/numa.h" | |
| #include "sysemu/runstate.h" | |
| #include "sysemu/sysemu.h" | |
| +#include "sysemu/cpus.h" | |
| +#include <linux/kvm.h> | |
| + | |
| +void qmp_hide_hypervisor(Error **errp) | |
| +{ | |
| + int32_t r; | |
| + CPUState *cpu; | |
| + | |
| + pause_all_vcpus(); | |
| + | |
| + CPU_FOREACH(cpu) { | |
| + X86CPU *x86_cpu = X86_CPU(cpu); | |
| + cpu_synchronize_state(cpu); | |
| + | |
| + struct { | |
| + struct kvm_cpuid2 cpuid; | |
| + struct kvm_cpuid_entry2 entries[KVM_MAX_CPUID_ENTRIES]; | |
| + } *cpuid_data = x86_cpu->cpuid_data; | |
| + | |
| + for (int32_t i = 0; i < cpuid_data->cpuid.nent; i++) { | |
| + struct kvm_cpuid_entry2 *entry = &cpuid_data->entries[i]; | |
| + | |
| + if (entry->function == 1) { | |
| + /* eax is 1, unset hypervisor bit */ | |
| + entry->ecx &= ~CPUID_EXT_HYPERVISOR; | |
| + break; | |
| + } | |
| + } | |
| + | |
| + r = kvm_vcpu_ioctl(cpu, KVM_SET_CPUID2, cpuid_data); | |
| + if (r) { | |
| + error_setg(errp, "KVM_SET_CPUID2 error"); | |
| + break; | |
| + } | |
| + } | |
| + | |
| + resume_all_vcpus(); | |
| +} | |
| CpuInfoList *qmp_query_cpus(Error **errp) | |
| { | |
| diff --git a/qapi/machine.json b/qapi/machine.json | |
| index 481b1f07ec..b256a17846 100644 | |
| --- a/qapi/machine.json | |
| +++ b/qapi/machine.json | |
| @@ -934,3 +934,12 @@ | |
| 'data': 'NumaOptions', | |
| 'allow-preconfig': true | |
| } | |
| + | |
| +## | |
| +# @hide-hypervisor: | |
| +# | |
| +# Hides the 'hypervisor' cpuid flag on all vCPUs at runtime. | |
| +## | |
| +{ | |
| + 'command': 'hide-hypervisor' | |
| +} | |
| diff --git a/target/i386/cpu.h b/target/i386/cpu.h | |
| index e1a5c174dc..5bc79c2bce 100644 | |
| --- a/target/i386/cpu.h | |
| +++ b/target/i386/cpu.h | |
| @@ -26,6 +26,8 @@ | |
| #include "exec/cpu-defs.h" | |
| #include "qapi/qapi-types-common.h" | |
| +#define KVM_MAX_CPUID_ENTRIES 100 | |
| + | |
| /* The x86 has a strong memory model with some store-after-load re-ordering */ | |
| #define TCG_GUEST_DEFAULT_MO (TCG_MO_ALL & ~TCG_MO_ST_LD) | |
| @@ -1759,6 +1761,8 @@ struct X86CPU { | |
| int32_t thread_id; | |
| int32_t hv_max_vps; | |
| + | |
| + void *cpuid_data; | |
| }; | |
| diff --git a/target/i386/kvm.c b/target/i386/kvm.c | |
| index f305474058..faa2c61d86 100644 | |
| --- a/target/i386/kvm.c | |
| +++ b/target/i386/kvm.c | |
| @@ -1456,8 +1456,6 @@ static int hyperv_init_vcpu(X86CPU *cpu) | |
| static Error *invtsc_mig_blocker; | |
| -#define KVM_MAX_CPUID_ENTRIES 100 | |
| - | |
| int kvm_arch_init_vcpu(CPUState *cs) | |
| { | |
| struct { | |
| @@ -1822,6 +1820,10 @@ int kvm_arch_init_vcpu(CPUState *cs) | |
| cpuid_data.cpuid.nent = cpuid_i; | |
| cpuid_data.cpuid.padding = 0; | |
| + | |
| + cpu->cpuid_data = malloc(sizeof(cpuid_data)); | |
| + memcpy(cpu->cpuid_data, &cpuid_data, sizeof(cpuid_data)); | |
| + | |
| r = kvm_vcpu_ioctl(cs, KVM_SET_CPUID2, &cpuid_data); | |
| if (r) { | |
| goto fail; | |
| -- | |
| 2.29.2 |
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make sure to configure with
../configure --target-list=x86_64-softmmuso it doesn't try to build all targets and fail.