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Message-ID: <4bd4a664-25c8-d86d-533a-d3dc338e0bec@loongson.cn>
Date: Fri, 12 Jul 2024 14:55:04 +0800
From: maobibo <maobibo@...ngson.cn>
To: Xianglai Li <lixianglai@...ngson.cn>, linux-kernel@...r.kernel.org
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>,
Huacai Chen <chenhuacai@...nel.org>, kvm@...r.kernel.org,
loongarch@...ts.linux.dev, Min Zhou <zhoumin@...ngson.cn>,
Paolo Bonzini <pbonzini@...hat.com>, WANG Xuerui <kernel@...0n.name>
Subject: Re: [PATCH 01/11] LoongArch: KVM: Add iocsr and mmio bus simulation
in kernel
On 2024/7/5 上午10:38, Xianglai Li wrote:
> Add iocsr and mmio memory read and write simulation to the kernel.
> When the VM accesses the device address space through iocsr
> instructions or mmio, it does not need to return to the qemu
> user mode but directly completes the access in the kernel mode.
>
> Signed-off-by: Tianrui Zhao <zhaotianrui@...ngson.cn>
> Signed-off-by: Xianglai Li <lixianglai@...ngson.cn>
> ---
> Cc: Bibo Mao <maobibo@...ngson.cn>
> Cc: Huacai Chen <chenhuacai@...nel.org>
> Cc: kvm@...r.kernel.org
> Cc: loongarch@...ts.linux.dev
> Cc: Min Zhou <zhoumin@...ngson.cn>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>
> Cc: WANG Xuerui <kernel@...0n.name>
> Cc: Xianglai li <lixianglai@...ngson.cn>
>
> arch/loongarch/kvm/exit.c | 69 ++++++++++++++++++++++++++++-----------
> include/linux/kvm_host.h | 1 +
> 2 files changed, 51 insertions(+), 19 deletions(-)
>
> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> index a68573e091c0..e8e37e135dd1 100644
> --- a/arch/loongarch/kvm/exit.c
> +++ b/arch/loongarch/kvm/exit.c
> @@ -148,7 +148,7 @@ static int kvm_handle_csr(struct kvm_vcpu *vcpu, larch_inst inst)
> int kvm_emu_iocsr(larch_inst inst, struct kvm_run *run, struct kvm_vcpu *vcpu)
> {
> int ret;
> - unsigned long val;
> + unsigned long *val;
> u32 addr, rd, rj, opcode;
>
> /*
> @@ -161,6 +161,7 @@ int kvm_emu_iocsr(larch_inst inst, struct kvm_run *run, struct kvm_vcpu *vcpu)
> ret = EMULATE_DO_IOCSR;
> run->iocsr_io.phys_addr = addr;
> run->iocsr_io.is_write = 0;
> + val = &vcpu->arch.gprs[rd];
>
> /* LoongArch is Little endian */
> switch (opcode) {
> @@ -194,15 +195,21 @@ int kvm_emu_iocsr(larch_inst inst, struct kvm_run *run, struct kvm_vcpu *vcpu)
> break;
> default:
> ret = EMULATE_FAIL;
> - break;
> + return ret;
How about directly return such as *return EMULATE_FAIL;* ?
> }
>
> - if (ret == EMULATE_DO_IOCSR) {
> - if (run->iocsr_io.is_write) {
> - val = vcpu->arch.gprs[rd];
> - memcpy(run->iocsr_io.data, &val, run->iocsr_io.len);
> - }
> - vcpu->arch.io_gpr = rd;
> + if (run->iocsr_io.is_write) {
> + if (!kvm_io_bus_write(vcpu, KVM_IOCSR_BUS, addr, run->iocsr_io.len, val))
It exceeds 80 chars, it will be better if line wrapper is added.
> + ret = EMULATE_DONE;
> + else
> + /* Save data and let user space to write it */
> + memcpy(run->iocsr_io.data, val, run->iocsr_io.len);
> + } else {
> + if (!kvm_io_bus_read(vcpu, KVM_IOCSR_BUS, addr, run->iocsr_io.len, val))
Ditto.
> + ret = EMULATE_DONE;
> + else
> + /* Save register id for iocsr read completion */
> + vcpu->arch.io_gpr = rd;
> }
>
> return ret;
> @@ -438,19 +445,33 @@ int kvm_emu_mmio_read(struct kvm_vcpu *vcpu, larch_inst inst)
> }
>
> if (ret == EMULATE_DO_MMIO) {
> + /*
> + * if mmio device such as pch pic is emulated in KVM,
> + * it need not return to user space to handle the mmio
> + * exception.
> + */
> + ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, vcpu->arch.badv,
> + run->mmio.len, &vcpu->arch.gprs[rd]);
> + if (!ret) {
> + update_pc(&vcpu->arch);
> + vcpu->mmio_needed = 0;
> + return EMULATE_DONE;
> + }
> +
> /* Set for kvm_complete_mmio_read() use */
> vcpu->arch.io_gpr = rd;
> run->mmio.is_write = 0;
> vcpu->mmio_is_write = 0;
> trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, run->mmio.len,
> run->mmio.phys_addr, NULL);
Should the trace function be called for KVM_MMIO_BUS also? I think the
trace function should be called before kvm_io_bus_read.
> - } else {
> - kvm_err("Read not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
> - inst.word, vcpu->arch.pc, vcpu->arch.badv);
> - kvm_arch_vcpu_dump_regs(vcpu);
> - vcpu->mmio_needed = 0;
> + return EMULATE_DO_MMIO;
> }
>
> + kvm_err("Read not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
> + inst.word, vcpu->arch.pc, vcpu->arch.badv);
> + kvm_arch_vcpu_dump_regs(vcpu);
> + vcpu->mmio_needed = 0;
> +
Empty line is not necessary from my view :)
> return ret;
> }
>
> @@ -591,19 +612,29 @@ int kvm_emu_mmio_write(struct kvm_vcpu *vcpu, larch_inst inst)
> }
>
> if (ret == EMULATE_DO_MMIO) {
> + /*
> + * if mmio device such as pch pic is emulated in KVM,
> + * it need not return to user space to handle the mmio
> + * exception.
> + */
> + ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, vcpu->arch.badv,
> + run->mmio.len, data);
> + if (!ret)
> + return EMULATE_DONE;
> +
> run->mmio.is_write = 1;
> vcpu->mmio_needed = 1;
> vcpu->mmio_is_write = 1;
> trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, run->mmio.len,
> run->mmio.phys_addr, data);
Ditto, trace function should be put before kvm_io_bus_write.
> - } else {
> - vcpu->arch.pc = curr_pc;
> - kvm_err("Write not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
> - inst.word, vcpu->arch.pc, vcpu->arch.badv);
> - kvm_arch_vcpu_dump_regs(vcpu);
> - /* Rollback PC if emulation was unsuccessful */
> + return EMULATE_DO_MMIO;
> }
>
> + vcpu->arch.pc = curr_pc;
> + kvm_err("Write not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
> + inst.word, vcpu->arch.pc, vcpu->arch.badv);
> + kvm_arch_vcpu_dump_regs(vcpu);
> + /* Rollback PC if emulation was unsuccessful */
> return ret;
> }
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 692c01e41a18..f51b2e53d81c 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -219,6 +219,7 @@ enum kvm_bus {
> KVM_PIO_BUS,
> KVM_VIRTIO_CCW_NOTIFY_BUS,
> KVM_FAST_MMIO_BUS,
> + KVM_IOCSR_BUS,
> KVM_NR_BUSES
> };
I just think this patch should be after PCH/EXTIOI/IPI is created and
IOCSR/MMIO space is registered in kernel space.It is only my points, I
am not good at this:(
Regards
Bibo Mao
>
>
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