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| author | Sean Christopherson <seanjc@google.com> | 2022-08-30 23:15:51 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-09-26 12:03:04 -0400 |
| commit | d500e1ed3dc873818277e109ccf6407118669236 (patch) | |
| tree | 439d3c0df39ac444e5bc7a23a790acbffe7059a2 /arch/x86/kvm/x86.c | |
| parent | 750f8fcb261ae350af7a2467721e76082b527cbf (diff) | |
| download | linux-d500e1ed3dc873818277e109ccf6407118669236.tar.gz | |
KVM: x86: Allow clearing RFLAGS.RF on forced emulation to test code #DBs
Extend force_emulation_prefix to an 'int' and use bit 1 as a flag to
indicate that KVM should clear RFLAGS.RF before emulating, e.g. to allow
tests to force emulation of code breakpoints in conjunction with MOV/POP
SS blocking, which is impossible without KVM intervention as VMX
unconditionally sets RFLAGS.RF on intercepted #UD.
Make the behavior controllable so that tests can also test RFLAGS.RF=1
(again in conjunction with code #DBs).
Note, clearing RFLAGS.RF won't create an infinite #DB loop as the guest's
IRET from the #DB handler will return to the instruction and not the
prefix, i.e. the restart won't force emulation.
Opportunistically convert the permissions to the preferred octal format.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-5-seanjc@google.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 418a069ab0d7..a7ae08e68582 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -173,8 +173,13 @@ bool __read_mostly enable_vmware_backdoor = false; module_param(enable_vmware_backdoor, bool, S_IRUGO); EXPORT_SYMBOL_GPL(enable_vmware_backdoor); -static bool __read_mostly force_emulation_prefix = false; -module_param(force_emulation_prefix, bool, S_IRUGO); +/* + * Flags to manipulate forced emulation behavior (any non-zero value will + * enable forced emulation). + */ +#define KVM_FEP_CLEAR_RFLAGS_RF BIT(1) +static int __read_mostly force_emulation_prefix; +module_param(force_emulation_prefix, int, 0444); int __read_mostly pi_inject_timer = -1; module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR); @@ -7255,6 +7260,8 @@ int handle_ud(struct kvm_vcpu *vcpu) kvm_read_guest_virt(vcpu, kvm_get_linear_rip(vcpu), sig, sizeof(sig), &e) == 0 && memcmp(sig, kvm_emulate_prefix, sizeof(sig)) == 0) { + if (force_emulation_prefix & KVM_FEP_CLEAR_RFLAGS_RF) + kvm_set_rflags(vcpu, kvm_get_rflags(vcpu) & ~X86_EFLAGS_RF); kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig)); emul_type = EMULTYPE_TRAP_UD_FORCED; } |