Commit 06d22a9c authored by Oliver Upton's avatar Oliver Upton Committed by Marc Zyngier
Browse files

KVM: arm64: Reload vCPU for accesses to OSLAR_EL1 



KVM takes ownership of the debug regs if the guest enables the OS lock,
as it needs to use MDSCR_EL1 to mask debug exceptions. Just reload the
vCPU if the guest toggles the OS lock, relying on kvm_vcpu_load_debug()
to update the debug owner and get the right trap configuration in place.

Tested-by: default avatarJames Clark <james.clark@linaro.org>
Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241219224116.3941496-13-oliver.upton@linux.dev


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent beb470d9

arch/arm64/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -1346,6 +1346,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu); 
void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);

void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu);

void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu);

void kvm_debug_handle_oslar(struct kvm_vcpu *vcpu, u64 val);



#define kvm_vcpu_os_lock_enabled(vcpu)		\

	(!!(__vcpu_sys_reg(vcpu, OSLSR_EL1) & OSLSR_EL1_OSLK))

arch/arm64/kvm/debug.c

+13 −0
Original line number Diff line number Diff line
@@ -288,3 +288,16 @@ void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu) 


	vcpu->arch.debug_owner = VCPU_DEBUG_GUEST_OWNED;

}



void kvm_debug_handle_oslar(struct kvm_vcpu *vcpu, u64 val)

{

	if (val & OSLAR_EL1_OSLK)

		__vcpu_sys_reg(vcpu, OSLSR_EL1) |= OSLSR_EL1_OSLK;

	else

		__vcpu_sys_reg(vcpu, OSLSR_EL1) &= ~OSLSR_EL1_OSLK;



	preempt_disable();

	kvm_arch_vcpu_put(vcpu);

	kvm_arch_vcpu_load(vcpu, smp_processor_id());

	preempt_enable();

}

arch/arm64/kvm/sys_regs.c

+1 −8
Original line number Diff line number Diff line
@@ -570,17 +570,10 @@ static bool trap_oslar_el1(struct kvm_vcpu *vcpu, 
			   struct sys_reg_params *p,

			   const struct sys_reg_desc *r)

{

	u64 oslsr;



	if (!p->is_write)

		return read_from_write_only(vcpu, p, r);



	/* Forward the OSLK bit to OSLSR */

	oslsr = __vcpu_sys_reg(vcpu, OSLSR_EL1) & ~OSLSR_EL1_OSLK;

	if (p->regval & OSLAR_EL1_OSLK)

		oslsr |= OSLSR_EL1_OSLK;



	__vcpu_sys_reg(vcpu, OSLSR_EL1) = oslsr;

	kvm_debug_handle_oslar(vcpu, p->regval);

	return true;

}