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LoongArch: KVM: Add hypercall service support for usermode VMM

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Some VMMs provides special hypercall service in usermode, KVM should not
handle the usermode hypercall service, thus pass it to usermode, let the
usermode VMM handle it.

Here a new code KVM_HCALL_CODE_USER_SERVICE is added for the user-mode
hypercall service, KVM lets all six registers visible to usermode VMM.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Bibo Mao 2025-01-13 21:37:17 +08:00 • committed by Huacai Chen
parent 4d38d0416e
commit 2737dee106
6 changed files with 42 additions and 1 deletions
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1
arch/loongarch/include/asm/kvm_host.h
View file

@ -162,6 +162,7 @@ enum emulation_result {
#define LOONGARCH_PV_FEAT_UPDATED BIT_ULL(63)
#define LOONGARCH_PV_FEAT_MASK (BIT(KVM_FEATURE_IPI) | \
BIT(KVM_FEATURE_STEAL_TIME) | \
BIT(KVM_FEATURE_USER_HCALL) | \
BIT(KVM_FEATURE_VIRT_EXTIOI))
struct kvm_vcpu_arch {

3
arch/loongarch/include/asm/kvm_para.h
View file

@ -13,6 +13,7 @@
#define KVM_HCALL_CODE_SERVICE 0
#define KVM_HCALL_CODE_SWDBG 1
#define KVM_HCALL_CODE_USER_SERVICE 2
#define KVM_HCALL_SERVICE HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SERVICE)
#define KVM_HCALL_FUNC_IPI 1
@ -20,6 +21,8 @@
#define KVM_HCALL_SWDBG HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SWDBG)
#define KVM_HCALL_USER_SERVICE HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_USER_SERVICE)
/*
* LoongArch hypercall return code
*/

1
arch/loongarch/include/asm/kvm_vcpu.h
View file

@ -43,6 +43,7 @@ int kvm_emu_mmio_read(struct kvm_vcpu *vcpu, larch_inst inst);
int kvm_emu_mmio_write(struct kvm_vcpu *vcpu, larch_inst inst);
int kvm_complete_mmio_read(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_complete_iocsr_read(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_complete_user_service(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_emu_idle(struct kvm_vcpu *vcpu);
int kvm_pending_timer(struct kvm_vcpu *vcpu);
int kvm_handle_fault(struct kvm_vcpu *vcpu, int fault);

1
arch/loongarch/include/uapi/asm/kvm_para.h
View file

@ -17,5 +17,6 @@
#define KVM_FEATURE_STEAL_TIME 2
/* BIT 24 - 31 are features configurable by user space vmm */
#define KVM_FEATURE_VIRT_EXTIOI 24
#define KVM_FEATURE_USER_HCALL 25
#endif /* _UAPI_ASM_KVM_PARA_H */

30
arch/loongarch/kvm/exit.c
View file

@ -709,6 +709,14 @@ static int kvm_handle_write_fault(struct kvm_vcpu *vcpu)
return kvm_handle_rdwr_fault(vcpu, true);
}
int kvm_complete_user_service(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
update_pc(&vcpu->arch);
kvm_write_reg(vcpu, LOONGARCH_GPR_A0, run->hypercall.ret);
return 0;
}
/**
* kvm_handle_fpu_disabled() - Guest used fpu however it is disabled at host
* @vcpu: Virtual CPU context.
@ -873,6 +881,28 @@ static int kvm_handle_hypercall(struct kvm_vcpu *vcpu)
vcpu->stat.hypercall_exits++;
kvm_handle_service(vcpu);
break;
case KVM_HCALL_USER_SERVICE:
if (!kvm_guest_has_pv_feature(vcpu, KVM_FEATURE_USER_HCALL)) {
kvm_write_reg(vcpu, LOONGARCH_GPR_A0, KVM_HCALL_INVALID_CODE);
break;
}
vcpu->stat.hypercall_exits++;
vcpu->run->exit_reason = KVM_EXIT_HYPERCALL;
vcpu->run->hypercall.nr = KVM_HCALL_USER_SERVICE;
vcpu->run->hypercall.args[0] = kvm_read_reg(vcpu, LOONGARCH_GPR_A0);
vcpu->run->hypercall.args[1] = kvm_read_reg(vcpu, LOONGARCH_GPR_A1);
vcpu->run->hypercall.args[2] = kvm_read_reg(vcpu, LOONGARCH_GPR_A2);
vcpu->run->hypercall.args[3] = kvm_read_reg(vcpu, LOONGARCH_GPR_A3);
vcpu->run->hypercall.args[4] = kvm_read_reg(vcpu, LOONGARCH_GPR_A4);
vcpu->run->hypercall.args[5] = kvm_read_reg(vcpu, LOONGARCH_GPR_A5);
vcpu->run->hypercall.flags = 0;
/*
* Set invalid return value by default, let user-mode VMM modify it.
*/
vcpu->run->hypercall.ret = KVM_HCALL_INVALID_CODE;
ret = RESUME_HOST;
break;
case KVM_HCALL_SWDBG:
/* KVM_HCALL_SWDBG only in effective when SW_BP is enabled */
if (vcpu->guest_debug & KVM_GUESTDBG_SW_BP_MASK) {

7
arch/loongarch/kvm/vcpu.c
View file

@ -1732,9 +1732,14 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
vcpu->mmio_needed = 0;
}
if (run->exit_reason == KVM_EXIT_LOONGARCH_IOCSR) {
switch (run->exit_reason) {
case KVM_EXIT_HYPERCALL:
kvm_complete_user_service(vcpu, run);
break;
case KVM_EXIT_LOONGARCH_IOCSR:
if (!run->iocsr_io.is_write)
kvm_complete_iocsr_read(vcpu, run);
break;
}
if (!vcpu->wants_to_run)