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Message-ID: <ab998710-637c-315b-ca49-8346f671abab@loongson.cn>
Date: Fri, 30 Jan 2026 09:32:22 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org, loongarch@...ts.linux.dev
Subject: Re: [PATCH] LoongArch: KVM: Set default return value in kvm IO bus
ops
On 2026/1/29 下午8:44, Huacai Chen wrote:
> Hi, Bibo,
>
> On Wed, Dec 10, 2025 at 10:56 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> When irqchip in kernel is enabled, its register area is registered
>> in the IO bus list with API kvm_io_bus_register_dev(). In MMIO/IOCSR
>> register access emulation, kvm_io_bus_write/kvm_io_bus_read is called
>> firstly. If it returns 0, it shows that in kernel irqchip handles
>> the emulation already, else it returns to VMM and lets VMM emulate
>> the register access.
>>
>> Once irqchip in kernel is enabled, it should return 0 if the address
>> is within range of the registered IO bus. It should not return to VMM
>> since VMM does not know how to handle it, and irqchip is handled in
>> kernel already.
>>
>> Here set default return value with 0 in KVM IO bus operations.
> If you are sure that both the good path and bad path should both
> return 0, please check whether mail_send() and send_ipi_data() should
> also change.
yes, there should be similiar modification with mail_send() and
send_ipi_data(). Will update the patch in next version.
Regards
Bibo Mao
>
> Huacai
>
>>
>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>> ---
>> arch/loongarch/kvm/intc/eiointc.c | 28 ++++++++++++----------------
>> arch/loongarch/kvm/intc/ipi.c | 10 ++--------
>> arch/loongarch/kvm/intc/pch_pic.c | 31 ++++++++++++++-----------------
>> 3 files changed, 28 insertions(+), 41 deletions(-)
>>
>> diff --git a/arch/loongarch/kvm/intc/eiointc.c b/arch/loongarch/kvm/intc/eiointc.c
>> index 29886876143f..7ca9dfea7f39 100644
>> --- a/arch/loongarch/kvm/intc/eiointc.c
>> +++ b/arch/loongarch/kvm/intc/eiointc.c
>> @@ -119,7 +119,7 @@ void eiointc_set_irq(struct loongarch_eiointc *s, int irq, int level)
>> static int loongarch_eiointc_read(struct kvm_vcpu *vcpu, struct loongarch_eiointc *s,
>> gpa_t addr, unsigned long *val)
>> {
>> - int index, ret = 0;
>> + int index;
>> u64 data = 0;
>> gpa_t offset;
>>
>> @@ -150,30 +150,29 @@ static int loongarch_eiointc_read(struct kvm_vcpu *vcpu, struct loongarch_eioint
>> data = s->coremap[index];
>> break;
>> default:
>> - ret = -EINVAL;
>> break;
>> }
>> *val = data;
>>
>> - return ret;
>> + return 0;
>> }
>>
>> static int kvm_eiointc_read(struct kvm_vcpu *vcpu,
>> struct kvm_io_device *dev,
>> gpa_t addr, int len, void *val)
>> {
>> - int ret = -EINVAL;
>> + int ret = 0;
>> unsigned long flags, data, offset;
>> struct loongarch_eiointc *eiointc = vcpu->kvm->arch.eiointc;
>>
>> if (!eiointc) {
>> kvm_err("%s: eiointc irqchip not valid!\n", __func__);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> if (addr & (len - 1)) {
>> kvm_err("%s: eiointc not aligned addr %llx len %d\n", __func__, addr, len);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> offset = addr & 0x7;
>> @@ -208,7 +207,7 @@ static int loongarch_eiointc_write(struct kvm_vcpu *vcpu,
>> struct loongarch_eiointc *s,
>> gpa_t addr, u64 value, u64 field_mask)
>> {
>> - int index, irq, ret = 0;
>> + int index, irq;
>> u8 cpu;
>> u64 data, old, mask;
>> gpa_t offset;
>> @@ -287,29 +286,28 @@ static int loongarch_eiointc_write(struct kvm_vcpu *vcpu,
>> eiointc_update_sw_coremap(s, index * 8, data, sizeof(data), true);
>> break;
>> default:
>> - ret = -EINVAL;
>> break;
>> }
>>
>> - return ret;
>> + return 0;
>> }
>>
>> static int kvm_eiointc_write(struct kvm_vcpu *vcpu,
>> struct kvm_io_device *dev,
>> gpa_t addr, int len, const void *val)
>> {
>> - int ret = -EINVAL;
>> + int ret = 0;
>> unsigned long flags, value;
>> struct loongarch_eiointc *eiointc = vcpu->kvm->arch.eiointc;
>>
>> if (!eiointc) {
>> kvm_err("%s: eiointc irqchip not valid!\n", __func__);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> if (addr & (len - 1)) {
>> kvm_err("%s: eiointc not aligned addr %llx len %d\n", __func__, addr, len);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> vcpu->stat.eiointc_write_exits++;
>> @@ -352,7 +350,7 @@ static int kvm_eiointc_virt_read(struct kvm_vcpu *vcpu,
>>
>> if (!eiointc) {
>> kvm_err("%s: eiointc irqchip not valid!\n", __func__);
>> - return -EINVAL;
>> + return 0;
>> }
>>
>> addr -= EIOINTC_VIRT_BASE;
>> @@ -383,21 +381,19 @@ static int kvm_eiointc_virt_write(struct kvm_vcpu *vcpu,
>>
>> if (!eiointc) {
>> kvm_err("%s: eiointc irqchip not valid!\n", __func__);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> addr -= EIOINTC_VIRT_BASE;
>> spin_lock_irqsave(&eiointc->lock, flags);
>> switch (addr) {
>> case EIOINTC_VIRT_FEATURES:
>> - ret = -EPERM;
>> break;
>> case EIOINTC_VIRT_CONFIG:
>> /*
>> * eiointc features can only be set at disabled status
>> */
>> if ((eiointc->status & BIT(EIOINTC_ENABLE)) && value) {
>> - ret = -EPERM;
>> break;
>> }
>> eiointc->status = value & eiointc->features;
>> diff --git a/arch/loongarch/kvm/intc/ipi.c b/arch/loongarch/kvm/intc/ipi.c
>> index 05cefd29282e..311cbb66821d 100644
>> --- a/arch/loongarch/kvm/intc/ipi.c
>> +++ b/arch/loongarch/kvm/intc/ipi.c
>> @@ -174,7 +174,7 @@ static int any_send(struct kvm *kvm, uint64_t data)
>> vcpu = kvm_get_vcpu_by_cpuid(kvm, cpu);
>> if (unlikely(vcpu == NULL)) {
>> kvm_err("%s: invalid target cpu: %d\n", __func__, cpu);
>> - return -EINVAL;
>> + return 0;
>> }
>> offset = data & 0xffff;
>>
>> @@ -183,7 +183,6 @@ static int any_send(struct kvm *kvm, uint64_t data)
>>
>> static int loongarch_ipi_readl(struct kvm_vcpu *vcpu, gpa_t addr, int len, void *val)
>> {
>> - int ret = 0;
>> uint32_t offset;
>> uint64_t res = 0;
>>
>> @@ -211,19 +210,17 @@ static int loongarch_ipi_readl(struct kvm_vcpu *vcpu, gpa_t addr, int len, void
>> if (offset + len > IOCSR_IPI_BUF_38 + 8) {
>> kvm_err("%s: invalid offset or len: offset = %d, len = %d\n",
>> __func__, offset, len);
>> - ret = -EINVAL;
>> break;
>> }
>> res = read_mailbox(vcpu, offset, len);
>> break;
>> default:
>> kvm_err("%s: unknown addr: %llx\n", __func__, addr);
>> - ret = -EINVAL;
>> break;
>> }
>> *(uint64_t *)val = res;
>>
>> - return ret;
>> + return 0;
>> }
>>
>> static int loongarch_ipi_writel(struct kvm_vcpu *vcpu, gpa_t addr, int len, const void *val)
>> @@ -239,7 +236,6 @@ static int loongarch_ipi_writel(struct kvm_vcpu *vcpu, gpa_t addr, int len, cons
>>
>> switch (offset) {
>> case IOCSR_IPI_STATUS:
>> - ret = -EINVAL;
>> break;
>> case IOCSR_IPI_EN:
>> spin_lock(&vcpu->arch.ipi_state.lock);
>> @@ -257,7 +253,6 @@ static int loongarch_ipi_writel(struct kvm_vcpu *vcpu, gpa_t addr, int len, cons
>> if (offset + len > IOCSR_IPI_BUF_38 + 8) {
>> kvm_err("%s: invalid offset or len: offset = %d, len = %d\n",
>> __func__, offset, len);
>> - ret = -EINVAL;
>> break;
>> }
>> write_mailbox(vcpu, offset, data, len);
>> @@ -273,7 +268,6 @@ static int loongarch_ipi_writel(struct kvm_vcpu *vcpu, gpa_t addr, int len, cons
>> break;
>> default:
>> kvm_err("%s: unknown addr: %llx\n", __func__, addr);
>> - ret = -EINVAL;
>> break;
>> }
>>
>> diff --git a/arch/loongarch/kvm/intc/pch_pic.c b/arch/loongarch/kvm/intc/pch_pic.c
>> index a698a73de399..773885f8d659 100644
>> --- a/arch/loongarch/kvm/intc/pch_pic.c
>> +++ b/arch/loongarch/kvm/intc/pch_pic.c
>> @@ -74,7 +74,7 @@ void pch_msi_set_irq(struct kvm *kvm, int irq, int level)
>>
>> static int loongarch_pch_pic_read(struct loongarch_pch_pic *s, gpa_t addr, int len, void *val)
>> {
>> - int ret = 0, offset;
>> + int offset;
>> u64 data = 0;
>> void *ptemp;
>>
>> @@ -121,34 +121,32 @@ static int loongarch_pch_pic_read(struct loongarch_pch_pic *s, gpa_t addr, int l
>> data = s->isr;
>> break;
>> default:
>> - ret = -EINVAL;
>> + break;
>> }
>> spin_unlock(&s->lock);
>>
>> - if (ret == 0) {
>> - offset = (addr - s->pch_pic_base) & 7;
>> - data = data >> (offset * 8);
>> - memcpy(val, &data, len);
>> - }
>> + offset = (addr - s->pch_pic_base) & 7;
>> + data = data >> (offset * 8);
>> + memcpy(val, &data, len);
>>
>> - return ret;
>> + return 0;
>> }
>>
>> static int kvm_pch_pic_read(struct kvm_vcpu *vcpu,
>> struct kvm_io_device *dev,
>> gpa_t addr, int len, void *val)
>> {
>> - int ret;
>> + int ret = 0;
>> struct loongarch_pch_pic *s = vcpu->kvm->arch.pch_pic;
>>
>> if (!s) {
>> kvm_err("%s: pch pic irqchip not valid!\n", __func__);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> if (addr & (len - 1)) {
>> kvm_err("%s: pch pic not aligned addr %llx len %d\n", __func__, addr, len);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> /* statistics of pch pic reading */
>> @@ -161,7 +159,7 @@ static int kvm_pch_pic_read(struct kvm_vcpu *vcpu,
>> static int loongarch_pch_pic_write(struct loongarch_pch_pic *s, gpa_t addr,
>> int len, const void *val)
>> {
>> - int ret = 0, offset;
>> + int offset;
>> u64 old, data, mask;
>> void *ptemp;
>>
>> @@ -226,29 +224,28 @@ static int loongarch_pch_pic_write(struct loongarch_pch_pic *s, gpa_t addr,
>> case PCH_PIC_ROUTE_ENTRY_START ... PCH_PIC_ROUTE_ENTRY_END:
>> break;
>> default:
>> - ret = -EINVAL;
>> break;
>> }
>> spin_unlock(&s->lock);
>>
>> - return ret;
>> + return 0;
>> }
>>
>> static int kvm_pch_pic_write(struct kvm_vcpu *vcpu,
>> struct kvm_io_device *dev,
>> gpa_t addr, int len, const void *val)
>> {
>> - int ret;
>> + int ret = 0;
>> struct loongarch_pch_pic *s = vcpu->kvm->arch.pch_pic;
>>
>> if (!s) {
>> kvm_err("%s: pch pic irqchip not valid!\n", __func__);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> if (addr & (len - 1)) {
>> kvm_err("%s: pch pic not aligned addr %llx len %d\n", __func__, addr, len);
>> - return -EINVAL;
>> + return ret;
>> }
>>
>> /* statistics of pch pic writing */
>>
>> base-commit: c9b47175e9131118e6f221cc8fb81397d62e7c91
>> --
>> 2.39.3
>>
>>
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