Commit 40aaa5b6 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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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: default avatarSean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-28-seanjc@google.com


Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 28c40b2c

arch/x86/kvm/x86.c

+4 −3
Original line number Original line Diff line number Diff line
@@ -179,7 +179,7 @@ EXPORT_SYMBOL_GPL(enable_vmware_backdoor); 
 */

 */

#define KVM_FEP_CLEAR_RFLAGS_RF	BIT(1)

#define KVM_FEP_CLEAR_RFLAGS_RF	BIT(1)

static int __read_mostly force_emulation_prefix;

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;

int __read_mostly pi_inject_timer = -1;

module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR);

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)

int handle_ud(struct kvm_vcpu *vcpu)

{

{

	static const char kvm_emulate_prefix[] = { __KVM_EMULATE_PREFIX };

	static const char kvm_emulate_prefix[] = { __KVM_EMULATE_PREFIX };

	int fep_flags = READ_ONCE(force_emulation_prefix);

	int emul_type = EMULTYPE_TRAP_UD;

	int emul_type = EMULTYPE_TRAP_UD;

	char sig[5]; /* ud2; .ascii "kvm" */

	char sig[5]; /* ud2; .ascii "kvm" */

	struct x86_exception e;

	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)))

	if (unlikely(!kvm_can_emulate_insn(vcpu, emul_type, NULL, 0)))

		return 1;

		return 1;





	if (force_emulation_prefix &&

	if (fep_flags &&

	    kvm_read_guest_virt(vcpu, kvm_get_linear_rip(vcpu),

	    kvm_read_guest_virt(vcpu, kvm_get_linear_rip(vcpu),

				sig, sizeof(sig), &e) == 0 &&

				sig, sizeof(sig), &e) == 0 &&

	    memcmp(sig, kvm_emulate_prefix, sizeof(sig)) == 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_set_rflags(vcpu, kvm_get_rflags(vcpu) & ~X86_EFLAGS_RF);

		kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig));

		kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig));

		emul_type = EMULTYPE_TRAP_UD_FORCED;

		emul_type = EMULTYPE_TRAP_UD_FORCED;