From 40aaa5b6dadc2cbdfff004c31fdd00b9684ff1a8 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 30 Aug 2022 23:16:14 +0000 Subject: KVM: x86: Allow force_emulation_prefix to be written without a reload Allow force_emulation_prefix to be written by privileged userspace without reloading KVM. The param does not have any persistent affects and is trivial to snapshot. Signed-off-by: Sean Christopherson Link: https://lore.kernel.org/r/20220830231614.3580124-28-seanjc@google.com Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'arch/x86/kvm') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c0d5d512edfa..a532b9dea57b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -179,7 +179,7 @@ EXPORT_SYMBOL_GPL(enable_vmware_backdoor); */ #define KVM_FEP_CLEAR_RFLAGS_RF BIT(1) static int __read_mostly force_emulation_prefix; -module_param(force_emulation_prefix, int, 0444); +module_param(force_emulation_prefix, int, 0644); int __read_mostly pi_inject_timer = -1; module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR); @@ -7287,6 +7287,7 @@ static int kvm_can_emulate_insn(struct kvm_vcpu *vcpu, int emul_type, int handle_ud(struct kvm_vcpu *vcpu) { static const char kvm_emulate_prefix[] = { __KVM_EMULATE_PREFIX }; + int fep_flags = READ_ONCE(force_emulation_prefix); int emul_type = EMULTYPE_TRAP_UD; char sig[5]; /* ud2; .ascii "kvm" */ struct x86_exception e; @@ -7294,11 +7295,11 @@ int handle_ud(struct kvm_vcpu *vcpu) if (unlikely(!kvm_can_emulate_insn(vcpu, emul_type, NULL, 0))) return 1; - if (force_emulation_prefix && + if (fep_flags && 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) + if (fep_flags & 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; -- cgit v1.2.3-58-ga151