Re: [PATCH v5 18/20] RISC-V: KVM: Add SBI v0.1 support

Alexander Graf
2019-08-23T08:04:58Z

On 22.08.19 10:46, Anup Patel wrote:
> From: Atish Patra <atish.patra@wdc.com>
>
> The KVM host kernel running in HS-mode needs to handle SBI calls coming
> from guest kernel running in VS-mode.
>
> This patch adds SBI v0.1 support in KVM RISC-V. All the SBI calls are
> implemented correctly except remote tlb flushes. For remote TLB flushes,
> we are doing full TLB flush and this will be optimized in future.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/riscv/include/asm/kvm_host.h | 2 +
> arch/riscv/kvm/Makefile | 2 +-
> arch/riscv/kvm/vcpu_exit.c | 3 +
> arch/riscv/kvm/vcpu_sbi.c | 119 ++++++++++++++++++++++++++++++
> 4 files changed, 125 insertions(+), 1 deletion(-)
> create mode 100644 arch/riscv/kvm/vcpu_sbi.c
>
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 2af3a179c08e..0b1eceaef59f 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -241,4 +241,6 @@ bool kvm_riscv_vcpu_has_interrupt(struct kvm_vcpu *vcpu);
> void kvm_riscv_vcpu_power_off(struct kvm_vcpu *vcpu);
> void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
>
> +int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu);
> +
> #endif /* __RISCV_KVM_HOST_H__ */
> diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
> index 3e0c7558320d..b56dc1650d2c 100644
> --- a/arch/riscv/kvm/Makefile
> +++ b/arch/riscv/kvm/Makefile
> @@ -9,6 +9,6 @@ ccflags-y := -Ivirt/kvm -Iarch/riscv/kvm
> kvm-objs := $(common-objs-y)
>
> kvm-objs += main.o vm.o vmid.o tlb.o mmu.o
> -kvm-objs += vcpu.o vcpu_exit.o vcpu_switch.o vcpu_timer.o
> +kvm-objs += vcpu.o vcpu_exit.o vcpu_switch.o vcpu_timer.o vcpu_sbi.o
>
> obj-$(CONFIG_KVM) += kvm.o
> diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
> index fbc04fe335ad..87b83fcf9a14 100644
> --- a/arch/riscv/kvm/vcpu_exit.c
> +++ b/arch/riscv/kvm/vcpu_exit.c
> @@ -534,6 +534,9 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
> (vcpu->arch.guest_context.hstatus & HSTATUS_STL))
> ret = stage2_page_fault(vcpu, run, scause, stval);
> break;
> + case EXC_SUPERVISOR_SYSCALL:
> + if (vcpu->arch.guest_context.hstatus & HSTATUS_SPV)
> + ret = kvm_riscv_vcpu_sbi_ecall(vcpu);
> default:
> break;
> };
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> new file mode 100644
> index 000000000000..5793202eb514
> --- /dev/null
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -0,0 +1,119 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/**
> + * Copyright (c) 2019 Western Digital Corporation or its affiliates.
> + *
> + * Authors:
> + * Atish Patra <atish.patra@wdc.com>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/kvm_host.h>
> +#include <asm/csr.h>
> +#include <asm/kvm_vcpu_timer.h>
> +
> +#define SBI_VERSION_MAJOR 0
> +#define SBI_VERSION_MINOR 1
> +
> +/* TODO: Handle traps due to unpriv load and redirect it back to VS-mode */

Ugh, another one of those? Can't you just figure out a way to recover
from the page fault? Also, you want to combine this with the instruction
load logic, so that we have a single place that guest address space
reads go through.

> +static unsigned long kvm_sbi_unpriv_load(const unsigned long *addr,
> + struct kvm_vcpu *vcpu)
> +{
> + unsigned long flags, val;
> + unsigned long __hstatus, __sstatus;
> +
> + local_irq_save(flags);
> + __hstatus = csr_read(CSR_HSTATUS);
> + __sstatus = csr_read(CSR_SSTATUS);
> + csr_write(CSR_HSTATUS, vcpu->arch.guest_context.hstatus | HSTATUS_SPRV);
> + csr_write(CSR_SSTATUS, vcpu->arch.guest_context.sstatus);
> + val = *addr;
> + csr_write(CSR_HSTATUS, __hstatus);
> + csr_write(CSR_SSTATUS, __sstatus);
> + local_irq_restore(flags);
> +
> + return val;
> +}
> +
> +static void kvm_sbi_system_shutdown(struct kvm_vcpu *vcpu, u32 type)
> +{
> + int i;
> + struct kvm_vcpu *tmp;
> +
> + kvm_for_each_vcpu(i, tmp, vcpu->kvm)
> + tmp->arch.power_off = true;
> + kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
> +
> + memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
> + vcpu->run->system_event.type = type;
> + vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
> +}
> +
> +int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu)
> +{
> + int ret = 1;
> + u64 next_cycle;
> + int vcpuid;
> + struct kvm_vcpu *remote_vcpu;
> + ulong dhart_mask;
> + struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> +
> + if (!cp)
> + return -EINVAL;
> + switch (cp->a7) {
> + case SBI_SET_TIMER:
> +#if __riscv_xlen == 32
> + next_cycle = ((u64)cp->a1 << 32) | (u64)cp->a0;
> +#else
> + next_cycle = (u64)cp->a0;
> +#endif
> + kvm_riscv_vcpu_timer_next_event(vcpu, next_cycle);

Ah, this is where the timer set happens. I still don't understand how
this takes the frequency bit into account?

> + break;
> + case SBI_CONSOLE_PUTCHAR:
> + /* Not implemented */
> + cp->a0 = -ENOTSUPP;
> + break;
> + case SBI_CONSOLE_GETCHAR:
> + /* Not implemented */
> + cp->a0 = -ENOTSUPP;
> + break;

These two should be covered by the default case.

> + case SBI_CLEAR_IPI:
> + kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_S_SOFT);
> + break;
> + case SBI_SEND_IPI:
> + dhart_mask = kvm_sbi_unpriv_load((unsigned long *)cp->a0, vcpu);
> + for_each_set_bit(vcpuid, &dhart_mask, BITS_PER_LONG) {
> + remote_vcpu = kvm_get_vcpu_by_id(vcpu->kvm, vcpuid);
> + kvm_riscv_vcpu_set_interrupt(remote_vcpu, IRQ_S_SOFT);
> + }
> + break;
> + case SBI_SHUTDOWN:
> + kvm_sbi_system_shutdown(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN);
> + ret = 0;
> + break;
> + case SBI_REMOTE_FENCE_I:
> + sbi_remote_fence_i(NULL);
> + break;
> + /*
> + * TODO: There should be a way to call remote hfence.bvma.
> + * Preferred method is now a SBI call. Until then, just flush
> + * all tlbs.
> + */
> + case SBI_REMOTE_SFENCE_VMA:
> + /*TODO: Parse vma range.*/
> + sbi_remote_sfence_vma(NULL, 0, 0);
> + break;
> + case SBI_REMOTE_SFENCE_VMA_ASID:
> + /*TODO: Parse vma range for given ASID */
> + sbi_remote_sfence_vma(NULL, 0, 0);
> + break;
> + default:
> + cp->a0 = ENOTSUPP;
> + break;

Please just send unsupported SBI events into user space.

Alex

> + };
> +
> + if (ret >= 0)
> + cp->sepc += 4;
> +
> + return ret;
> +}
>