[PATCH] RISC-V: KVM: Redirect AMO load/store misaligned traps to guest

[Anup Patel]

On Sat, May 20, 2023 at 8:31 PM wchen <waylingii at gmail.com> wrote:
>
> The M-mode redirects an unhandled misaligned trap back
> to S-mode when not delegating it to VS-mode(hedeleg).
> However, KVM running in HS-mode terminates the VS-mode
> software when back from M-mode.
> The KVM should redirect the trap back to VS-mode, and
> let VS-mode trap handler decide the next step.
> Here is a way to handle misaligned traps in KVM,
> not only directing them to VS-mode or terminate it.
>
> Signed-off-by: wchen <waylingII at gmail.com>

Looks good to me.

Reviewed-by: Anup Patel <anup at brainfault.org>

Regards,
Anup

> ---
>  arch/riscv/include/asm/csr.h | 2 ++
>  arch/riscv/kvm/vcpu_exit.c   | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index b6acb7ed1..917814a0f 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -82,7 +82,9 @@
>  #define EXC_INST_ACCESS                1
>  #define EXC_INST_ILLEGAL       2
>  #define EXC_BREAKPOINT         3
> +#define EXC_LOAD_MISALIGNED    4
>  #define EXC_LOAD_ACCESS                5
> +#define EXC_STORE_MISALIGNED   6
>  #define EXC_STORE_ACCESS       7
>  #define EXC_SYSCALL            8
>  #define EXC_HYPERVISOR_SYSCALL 9
> diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
> index 4ea101a73..2415722c0 100644
> --- a/arch/riscv/kvm/vcpu_exit.c
> +++ b/arch/riscv/kvm/vcpu_exit.c
> @@ -183,6 +183,8 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>         run->exit_reason = KVM_EXIT_UNKNOWN;
>         switch (trap->scause) {
>         case EXC_INST_ILLEGAL:
> +       case EXC_LOAD_MISALIGNED:
> +       case EXC_STORE_MISALIGNED:
>                 if (vcpu->arch.guest_context.hstatus & HSTATUS_SPV) {
>                         kvm_riscv_vcpu_trap_redirect(vcpu, trap);
>                         ret = 1;
> --
> 2.34.1
>