diff mbox series

[2/6] RISC-V: KVM: Change the SBI specification version to v2.0

Message ID 20231010170503.657189-3-apatel@ventanamicro.com
State New
Headers
Series RISC-V SBI debug console extension support |

Commit Message

Anup Patel Oct. 10, 2023, 5:04 p.m. UTC 
  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@ventanamicro.com>
---
 arch/riscv/include/asm/kvm_vcpu_sbi.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Greg KH Oct. 10, 2023, 5:13 p.m. UTC | #1 
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@ventanamicro.com>
> ---
>  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?

thanks,

greg k-h
Anup Patel Oct. 11, 2023, 6:19 a.m. UTC | #2 
On Tue, Oct 10, 2023 at 10:43 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> 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@ventanamicro.com>
> > ---
> >  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
Greg KH Oct. 11, 2023, 7:27 a.m. UTC | #3 
On Wed, Oct 11, 2023 at 11:49:14AM +0530, Anup Patel wrote:
> On Tue, Oct 10, 2023 at 10:43 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> 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@ventanamicro.com>
> > > ---
> > >  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.

Is this api backwards compatible, or did you just break existing
userspace that only expects version 1.0?

thanks,

greg k-h
Anup Patel Oct. 11, 2023, 11:02 a.m. UTC | #4 
On Wed, Oct 11, 2023 at 12:57 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Wed, Oct 11, 2023 at 11:49:14AM +0530, Anup Patel wrote:
> > On Tue, Oct 10, 2023 at 10:43 PM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> 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@ventanamicro.com>
> > > > ---
> > > >  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.
>
> Is this api backwards compatible, or did you just break existing
> userspace that only expects version 1.0?

The legacy sbi_console_putchar() and sbi_console_getchar()
functions have not changed so it does not break existing
user-space.

The new SBI DBCN functions to be implemented by KVM
user space are:
sbi_debug_console_write()
sbi_debug_console_read()
sbi_debug_console_write_byte()

>
> thanks,
>
> greg k-h

Regards,
Anup
Greg KH Oct. 11, 2023, 3:26 p.m. UTC | #5 
On Wed, Oct 11, 2023 at 04:32:22PM +0530, Anup Patel wrote:
> On Wed, Oct 11, 2023 at 12:57 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Wed, Oct 11, 2023 at 11:49:14AM +0530, Anup Patel wrote:
> > > On Tue, Oct 10, 2023 at 10:43 PM Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org> 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@ventanamicro.com>
> > > > > ---
> > > > >  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.
> >
> > Is this api backwards compatible, or did you just break existing
> > userspace that only expects version 1.0?
> 
> The legacy sbi_console_putchar() and sbi_console_getchar()
> functions have not changed so it does not break existing
> user-space.
> 
> The new SBI DBCN functions to be implemented by KVM
> user space are:
> sbi_debug_console_write()
> sbi_debug_console_read()
> sbi_debug_console_write_byte()

And where exactly is that code for us to review that this is tested?

thanks,

greg k-h
Anup Patel Oct. 11, 2023, 3:38 p.m. UTC | #6 
On Wed, Oct 11, 2023 at 8:56 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Wed, Oct 11, 2023 at 04:32:22PM +0530, Anup Patel wrote:
> > On Wed, Oct 11, 2023 at 12:57 PM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Wed, Oct 11, 2023 at 11:49:14AM +0530, Anup Patel wrote:
> > > > On Tue, Oct 10, 2023 at 10:43 PM Greg Kroah-Hartman
> > > > <gregkh@linuxfoundation.org> 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@ventanamicro.com>
> > > > > > ---
> > > > > >  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.
> > >
> > > Is this api backwards compatible, or did you just break existing
> > > userspace that only expects version 1.0?
> >
> > The legacy sbi_console_putchar() and sbi_console_getchar()
> > functions have not changed so it does not break existing
> > user-space.
> >
> > The new SBI DBCN functions to be implemented by KVM
> > user space are:
> > sbi_debug_console_write()
> > sbi_debug_console_read()
> > sbi_debug_console_write_byte()
>
> And where exactly is that code for us to review that this is tested?

The KVM selftests for KVM RISC-V are under development. Eventually,
we will have dedicated KVM selftests for the SBI extensions implemented
by KVM RISC-V.

Until then we have KVMTOOL implementation for SBI DBCN, which is
available in riscv_sbi_dbcn_v1 branch at:
https://github.com/avpatel/kvmtool.git

>
> thanks,
>
> greg k-h

Regards,
Anup
diff mbox series

Patch

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
 #define KVM_SBI_VERSION_MINOR 0
 
 enum kvm_riscv_sbi_ext_status {