RISC-V: KVM: Add remote HFENCE functions based on VCPU requests
The generic KVM has support for VCPU requests which can be used to do arch-specific work in the run-loop. We introduce remote HFENCE functions which will internally use VCPU requests instead of host SBI calls. Advantages of doing remote HFENCEs as VCPU requests are: 1) Multiple VCPUs of a Guest may be running on different Host CPUs so it is not always possible to determine the Host CPU mask for doing Host SBI call. For example, when VCPU X wants to do HFENCE on VCPU Y, it is possible that VCPU Y is blocked or in user-space (i.e. vcpu->cpu < 0). 2) To support nested virtualization, we will be having a separate shadow G-stage for each VCPU and a common host G-stage for the entire Guest/VM. The VCPU requests based remote HFENCEs helps us easily synchronize the common host G-stage and shadow G-stage of each VCPU without any additional IPI calls. This is also a preparatory patch for upcoming nested virtualization support where we will be having a shadow G-stage page table for each Guest VCPU. Signed-off-by: Anup Patel <apatel@ventanamicro.com> Reviewed-by: Atish Patra <atishp@rivosinc.com> Signed-off-by: Anup Patel <anup@brainfault.org>
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