On Tue, Oct 10, 2023 at 10:43 PM Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Oct 10, 2023 at 10:34:59PM +0530, Anup Patel wrote: > > We will be implementing SBI DBCN extension for KVM RISC-V so let > > us change the KVM RISC-V SBI specification version to v2.0. > > > > Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx> > > --- > > arch/riscv/include/asm/kvm_vcpu_sbi.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h > > index cdcf0ff07be7..8d6d4dce8a5e 100644 > > --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h > > +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h > > @@ -11,7 +11,7 @@ > > > > #define KVM_SBI_IMPID 3 > > > > -#define KVM_SBI_VERSION_MAJOR 1 > > +#define KVM_SBI_VERSION_MAJOR 2 > > What does this number mean? Who checks it? Why do you have to keep > incrementing it? This number is the SBI specification version implemented by KVM RISC-V for the Guest kernel. The original sbi_console_putchar() and sbi_console_getchar() are legacy functions (aka SBI v0.1) which were introduced a few years back along with the Linux RISC-V port. The latest SBI v2.0 specification (which is now frozen) introduces a new SBI debug console extension which replaces legacy sbi_console_putchar() and sbi_console_getchar() functions with better alternatives. (Refer, https://github.com/riscv-non-isa/riscv-sbi-doc/releases/download/commit-fe4562532a9cc57e5743b6466946c5e5c98c73ca/riscv-sbi.pdf) This series adds SBI debug console implementation in KVM RISC-V so the SBI specification version advertised by KVM RISC-V must also be upgraded to v2.0. Regarding who checks its, the SBI client drivers in the Linux kernel will check SBI specification version implemented by higher privilege mode (M-mode firmware or HS-mode hypervisor) before probing the SBI extension. For example, the HVC SBI driver (PATCH5) will ensure SBI spec version to be at least v2.0 before probing SBI debug console extension. > > thanks, > > greg k-h Regards, Anup
