Commit 8800b7c4 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm64: Add RMW specific sysreg accessor 



In a number of cases, we perform a Read-Modify-Write operation on
a system register, meaning that we would apply the RESx masks twice.

Instead, provide a new accessor that performs this RMW operation,
allowing the masks to be applied exactly once per operation.

Reviewed-by: default avatarMiguel Luis <miguel.luis@oracle.com>
Reviewed-by: default avatarOliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250603070824.1192795-3-maz@kernel.org


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 6678791e

arch/arm64/include/asm/kvm_host.h

+11 −0
Original line number Diff line number Diff line
@@ -1118,6 +1118,17 @@ u64 kvm_vcpu_apply_reg_masks(const struct kvm_vcpu *, enum vcpu_sysreg, u64); 
		ctxt_sys_reg(ctxt, (r)) = __v;				\

	} while (0)



#define __vcpu_rmw_sys_reg(v, r, op, val)				\

	do {								\

		const struct kvm_cpu_context *ctxt = &(v)->arch.ctxt;	\

		u64 __v = ctxt_sys_reg(ctxt, (r));			\

		__v op (val);						\

		if (vcpu_has_nv((v)) && (r) >= __SANITISED_REG_START__)	\

			__v = kvm_vcpu_apply_reg_masks((v), (r), __v);	\

									\

		ctxt_sys_reg(ctxt, (r)) = __v;				\

	} while (0)



#define __vcpu_sys_reg(v,r)						\

	(*({								\

		const struct kvm_cpu_context *ctxt = &(v)->arch.ctxt;	\

arch/arm64/kvm/debug.c

+2 −2
Original line number Diff line number Diff line
@@ -216,9 +216,9 @@ void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu) 
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;

		__vcpu_rmw_sys_reg(vcpu, OSLSR_EL1, |=, OSLSR_EL1_OSLK);

	else

		__vcpu_sys_reg(vcpu, OSLSR_EL1) &= ~OSLSR_EL1_OSLK;

		__vcpu_rmw_sys_reg(vcpu, OSLSR_EL1, &=, ~OSLSR_EL1_OSLK);



	preempt_disable();

	kvm_arch_vcpu_put(vcpu);

arch/arm64/kvm/hyp/vhe/sysreg-sr.c

+2 −2
Original line number Diff line number Diff line
@@ -70,8 +70,8 @@ static void __sysreg_save_vel2_state(struct kvm_vcpu *vcpu) 
		 */

		val = read_sysreg_el1(SYS_CNTKCTL);

		val &= CNTKCTL_VALID_BITS;

		__vcpu_sys_reg(vcpu, CNTHCTL_EL2) &= ~CNTKCTL_VALID_BITS;

		__vcpu_sys_reg(vcpu, CNTHCTL_EL2) |= val;

		__vcpu_rmw_sys_reg(vcpu, CNTHCTL_EL2, &=, ~CNTKCTL_VALID_BITS);

		__vcpu_rmw_sys_reg(vcpu, CNTHCTL_EL2, |=, val);

	}



	__vcpu_assign_sys_reg(vcpu, SP_EL2,	 read_sysreg(sp_el1));

arch/arm64/kvm/nested.c

+1 −1
Original line number Diff line number Diff line
@@ -1757,7 +1757,7 @@ int kvm_init_nv_sysregs(struct kvm_vcpu *vcpu) 


out:

	for (enum vcpu_sysreg sr = __SANITISED_REG_START__; sr < NR_SYS_REGS; sr++)

		(void)__vcpu_sys_reg(vcpu, sr);

		__vcpu_rmw_sys_reg(vcpu, sr, |=, 0);



	return 0;

}

arch/arm64/kvm/pmu-emul.c

+5 −5
Original line number Diff line number Diff line
@@ -510,7 +510,7 @@ static void kvm_pmu_counter_increment(struct kvm_vcpu *vcpu, 
			continue;



		/* Mark overflow */

		__vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(i);

		__vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, BIT(i));



		if (kvm_pmu_counter_can_chain(pmc))

			kvm_pmu_counter_increment(vcpu, BIT(i + 1),
@@ -556,7 +556,7 @@ static void kvm_pmu_perf_overflow(struct perf_event *perf_event, 
	perf_event->attr.sample_period = period;

	perf_event->hw.sample_period = period;



	__vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(idx);

	__vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, BIT(idx));



	if (kvm_pmu_counter_can_chain(pmc))

		kvm_pmu_counter_increment(vcpu, BIT(idx + 1),
@@ -914,9 +914,9 @@ void kvm_vcpu_reload_pmu(struct kvm_vcpu *vcpu) 
{

	u64 mask = kvm_pmu_implemented_counter_mask(vcpu);



	__vcpu_sys_reg(vcpu, PMOVSSET_EL0) &= mask;

	__vcpu_sys_reg(vcpu, PMINTENSET_EL1) &= mask;

	__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) &= mask;

	__vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, &=, mask);

	__vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, &=, mask);

	__vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, &=, mask);



	kvm_pmu_reprogram_counter_mask(vcpu, mask);

}