This RFC series adds initial support for the Ssqosid extension and the
sqoscfg CSR as specified in Chapter 2 of the RISC-V Capacity and
Bandwidth Controller QoS Register Interface (CBQRI) specification [1].
QoS (Quality of Service) in this context is concerned with shared
resources on an SoC such as cache capacity and memory bandwidth. Intel
and AMD already have QoS features on x86, and there is an existing user
interface in Linux: the resctrl virtual filesystem [2].
The sqoscfg CSR provides a mechanism by which a software workload (e.g.
a process or a set of processes) can be associated with a resource
control ID (RCID) and a monitoring counter ID (MCID) that accompanies
each request made by the hart to shared resources like cache. CBQRI
defines operations to configure resource usage limits, in the form of
capacity or bandwidth, for an RCID. CBQRI also defines operations to
configure counters to track the resource utilization of an MCID.
The CBQRI spec is still in draft state and is undergoing review [3]. It
is possible there will be changes to the Ssqosid extension and the CBQRI
spec. For example, the CSR address for sqoscfg is not yet finalized.
My goal for this RFC is to determine if the 2nd patch is an acceptable
approach to handling sqoscfg when switching tasks. This RFC was tested
against a QEMU branch that implements the Ssqosid extension [4]. A test
driver [5] was used to set thread_struct.sqoscfg for the current
process. This allowed __qos_sched_in() to be tested without resctrl.
A forthcoming RFC series will enable resctrl to support systems that
implement CBQRI and will reference a QEMU branch that implements CBQRI.
NOTE: CBQRI was previously known as CMQRI and the github repo with the
spec has not yet been renamed [6].
[1] https://github.com/riscv-non-isa/riscv-cmqri/blob/main/riscv-cbqri.pdf
[2] https://docs.kernel.org/x86/resctrl.html
[3] https://lists.riscv.org/g/tech-cmqri/message/38
[4] https://github.com/pdp7/qemu/tree/ssqosid_v8.0.0-rc1
[5] https://github.com/pdp7/linux/commits/ssqosid_sqoscfg_v6.3
[6] https://lists.riscv.org/g/tech-cmqri/message/41
Drew Fustini (1):
RISC-V: Add support for sqoscfg CSR
Kornel Dulęba (1):
RISC-V: Detect the Ssqosid extension
arch/riscv/Kconfig | 19 ++++++++++++++
arch/riscv/include/asm/csr.h | 8 ++++++
arch/riscv/include/asm/hwcap.h | 2 ++
arch/riscv/include/asm/processor.h | 3 +++
arch/riscv/include/asm/qos.h | 40 ++++++++++++++++++++++++++++++
arch/riscv/include/asm/switch_to.h | 2 ++
arch/riscv/kernel/cpu.c | 1 +
arch/riscv/kernel/cpufeature.c | 1 +
8 files changed, 76 insertions(+)
create mode 100644 arch/riscv/include/asm/qos.h
base-commit: d34a6b715a23ccd9c9d0bc7a475bea59dc3e28b2
--
2.34.1
Add support for the sqoscfg CSR defined in the Ssqosid ISA extension
(Supervisor-mode Quality of Service ID). The CSR contains two fields:
- Resource Control ID (RCID) used determine resource allocation
- Monitoring Counter ID (MCID) used to track resource usage
Requests from a hart to shared resources like cache will be tagged with
these IDs. This allows the usage of shared resources to be associated
with the task currently running on the hart.
A sqoscfg field is added to thread_struct and has the same format as the
sqoscfg CSR. This allows the scheduler to set the hart's sqoscfg CSR to
contain the RCID and MCID for the task that is being scheduled in. The
sqoscfg CSR is only written to if the thread_struct.sqoscfg is different
from the current value of the CSR.
A per-cpu variable cpu_sqoscfg is used to mirror that state of the CSR.
This is because access to L1D hot memory should be several times faster
than a CSR read. Also, in the case of virtualization, accesses to this
CSR are trapped in the hypervisor.
Link: https://github.com/riscv-non-isa/riscv-cmqri/blob/main/riscv-cbqri.pdf
Co-developed-by: Kornel Dulęba <[email protected]>
Signed-off-by: Kornel Dulęba <[email protected]>
Signed-off-by: Drew Fustini <[email protected]>
---
Note: the Ssqosid extension and CBQRI spec are still in a draft state.
The CSR address of sqoscfg is not final.
Changes from the original patch [1]:
- Rebase from 6.0 to 6.3
- Simplify per-cpu variable from struct to u32 with just sqoscfg
- Move qoscfg to thread_struct in arch/riscv/include/asm/processor.h
This avoids changing task_struct in /include/linux/sched.h
- Reword commit description
- Reword Kconfig description
[1] https://github.com/rivosinc/linux/commit/8454b793a62be21d39e5826ef5241dfa06198ba9
arch/riscv/Kconfig | 19 ++++++++++++++
arch/riscv/include/asm/csr.h | 8 ++++++
arch/riscv/include/asm/processor.h | 3 +++
arch/riscv/include/asm/qos.h | 40 ++++++++++++++++++++++++++++++
arch/riscv/include/asm/switch_to.h | 2 ++
5 files changed, 72 insertions(+)
create mode 100644 arch/riscv/include/asm/qos.h
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index cc02eb9eee1f..03f22b7fe34b 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -418,6 +418,25 @@ config RISCV_ISA_SVNAPOT
If you don't know what to do here, say Y.
+config RISCV_ISA_SSQOSID
+ bool "Ssqosid extension support"
+ default y
+ help
+ Adds support for the Ssqosid ISA extension (Supervisor-mode
+ Quality of Service ID).
+
+ Ssqosid defines the sqoscfg CSR which allows the system to tag
+ the running process with RCID (Resource Control ID) and MCID
+ (Monitoring Counter ID). The RCID is used determine resource
+ allocation. The MCID is used to track resource usage in event
+ counters.
+
+ For example, a cache controller may use the RCID to apply a
+ cache partitioning scheme and use the MCID to track how much
+ cache a process, or a group of processes, is using.
+
+ If you don't know what to do here, say Y.
+
config RISCV_ISA_SVPBMT
bool "SVPBMT extension support"
depends on 64BIT && MMU
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 7c2b8cdb7b77..17d04a0cacd6 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -59,6 +59,13 @@
#define SATP_ASID_MASK _AC(0xFFFF, UL)
#endif
+/* SQOSCFG fields */
+#define SQOSCFG_RCID_MASK _AC(0x00000FFF, UL)
+#define SQOSCFG_MCID_MASK SQOSCFG_RCID_MASK
+#define SQOSCFG_MCID_SHIFT 16
+#define SQOSCFG_MASK ((SQOSCFG_MCID_MASK << SQOSCFG_MCID_SHIFT) | \
+ SQOSCFG_RCID_MASK)
+
/* Exception cause high bit - is an interrupt if set */
#define CAUSE_IRQ_FLAG (_AC(1, UL) << (__riscv_xlen - 1))
@@ -245,6 +252,7 @@
#define CSR_STVAL 0x143
#define CSR_SIP 0x144
#define CSR_SATP 0x180
+#define CSR_SQOSCFG 0x181
#define CSR_STIMECMP 0x14D
#define CSR_STIMECMPH 0x15D
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 94a0590c6971..724b2aa2732d 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -39,6 +39,9 @@ struct thread_struct {
unsigned long s[12]; /* s[0]: frame pointer */
struct __riscv_d_ext_state fstate;
unsigned long bad_cause;
+#ifdef CONFIG_RISCV_ISA_SSQOSID
+ u32 sqoscfg;
+#endif
};
/* Whitelist the fstate from the task_struct for hardened usercopy */
diff --git a/arch/riscv/include/asm/qos.h b/arch/riscv/include/asm/qos.h
new file mode 100644
index 000000000000..297e7fb64d80
--- /dev/null
+++ b/arch/riscv/include/asm/qos.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_RISCV_QOS_H
+#define _ASM_RISCV_QOS_H
+
+#ifdef CONFIG_RISCV_ISA_SSQOSID
+
+#include <linux/sched.h>
+#include <linux/jump_label.h>
+
+#include <asm/barrier.h>
+#include <asm/csr.h>
+#include <asm/hwcap.h>
+
+/* cached value of sqoscfg csr for each cpu */
+static DEFINE_PER_CPU(u32, cpu_sqoscfg);
+
+static void __qos_sched_in(struct task_struct *task)
+{
+ u32 *cpu_sqoscfg_ptr = this_cpu_ptr(&cpu_sqoscfg);
+ u32 thread_sqoscfg;
+
+ thread_sqoscfg = READ_ONCE(task->thread.sqoscfg);
+
+ if (thread_sqoscfg != *cpu_sqoscfg_ptr) {
+ *cpu_sqoscfg_ptr = thread_sqoscfg;
+ csr_write(CSR_SQOSCFG, thread_sqoscfg);
+ }
+}
+
+static inline void qos_sched_in(struct task_struct *task)
+{
+ if (riscv_has_extension_likely(RISCV_ISA_EXT_SSQOSID))
+ __qos_sched_in(task);
+}
+#else
+
+static inline void qos_sched_in(struct task_struct *task) {}
+
+#endif /* CONFIG_RISCV_ISA_SSQOSID */
+#endif /* _ASM_RISCV_QOS_H */
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index 60f8ca01d36e..75d9bfd766af 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -12,6 +12,7 @@
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/csr.h>
+#include <asm/qos.h>
#ifdef CONFIG_FPU
extern void __fstate_save(struct task_struct *save_to);
@@ -79,6 +80,7 @@ do { \
if (has_fpu()) \
__switch_to_aux(__prev, __next); \
((last) = __switch_to(__prev, __next)); \
+ qos_sched_in(__next); \
} while (0)
#endif /* _ASM_RISCV_SWITCH_TO_H */
--
2.34.1
Hey Drew,
(Don't get your hopes up, I don't have anything really meaningful to
contribute, sorry.)
On Sun, Apr 09, 2023 at 09:36:46PM -0700, Drew Fustini wrote:
> Add support for the sqoscfg CSR defined in the Ssqosid ISA extension
> (Supervisor-mode Quality of Service ID). The CSR contains two fields:
>
> - Resource Control ID (RCID) used determine resource allocation
> - Monitoring Counter ID (MCID) used to track resource usage
>
> Requests from a hart to shared resources like cache will be tagged with
> these IDs. This allows the usage of shared resources to be associated
> with the task currently running on the hart.
>
> A sqoscfg field is added to thread_struct and has the same format as the
> sqoscfg CSR. This allows the scheduler to set the hart's sqoscfg CSR to
> contain the RCID and MCID for the task that is being scheduled in. The
> sqoscfg CSR is only written to if the thread_struct.sqoscfg is different
> from the current value of the CSR.
>
> A per-cpu variable cpu_sqoscfg is used to mirror that state of the CSR.
> This is because access to L1D hot memory should be several times faster
> than a CSR read. Also, in the case of virtualization, accesses to this
> CSR are trapped in the hypervisor.
>
> Link: https://github.com/riscv-non-isa/riscv-cmqri/blob/main/riscv-cbqri.pdf
> Co-developed-by: Kornel Dulęba <[email protected]>
> Signed-off-by: Kornel Dulęba <[email protected]>
> Signed-off-by: Drew Fustini <[email protected]>
> ---
> Note: the Ssqosid extension and CBQRI spec are still in a draft state.
> The CSR address of sqoscfg is not final.
>
> Changes from the original patch [1]:
> - Rebase from 6.0 to 6.3
> - Simplify per-cpu variable from struct to u32 with just sqoscfg
> - Move qoscfg to thread_struct in arch/riscv/include/asm/processor.h
> This avoids changing task_struct in /include/linux/sched.h
> - Reword commit description
> - Reword Kconfig description
>
> [1] https://github.com/rivosinc/linux/commit/8454b793a62be21d39e5826ef5241dfa06198ba9
>
> arch/riscv/Kconfig | 19 ++++++++++++++
> arch/riscv/include/asm/csr.h | 8 ++++++
> arch/riscv/include/asm/processor.h | 3 +++
> arch/riscv/include/asm/qos.h | 40 ++++++++++++++++++++++++++++++
> arch/riscv/include/asm/switch_to.h | 2 ++
> 5 files changed, 72 insertions(+)
> create mode 100644 arch/riscv/include/asm/qos.h
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index cc02eb9eee1f..03f22b7fe34b 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -418,6 +418,25 @@ config RISCV_ISA_SVNAPOT
>
> If you don't know what to do here, say Y.
>
> +config RISCV_ISA_SSQOSID
> + bool "Ssqosid extension support"
> + default y
> + help
> + Adds support for the Ssqosid ISA extension (Supervisor-mode
> + Quality of Service ID).
Could you add "long form" text in brackets here to the bool line, a la:
https://patchwork.kernel.org/project/linux-riscv/patch/20230405-pucker-cogwheel-3a999a94a2f2@wendy/
> +
> + Ssqosid defines the sqoscfg CSR which allows the system to tag
> + the running process with RCID (Resource Control ID) and MCID
> + (Monitoring Counter ID). The RCID is used determine resource
> + allocation. The MCID is used to track resource usage in event
> + counters.
> +
> + For example, a cache controller may use the RCID to apply a
> + cache partitioning scheme and use the MCID to track how much
> + cache a process, or a group of processes, is using.
> +
> + If you don't know what to do here, say Y.
> +
> config RISCV_ISA_SVPBMT
> bool "SVPBMT extension support"
> depends on 64BIT && MMU
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index 7c2b8cdb7b77..17d04a0cacd6 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -59,6 +59,13 @@
> #define SATP_ASID_MASK _AC(0xFFFF, UL)
> #endif
>
> +/* SQOSCFG fields */
> +#define SQOSCFG_RCID_MASK _AC(0x00000FFF, UL)
> +#define SQOSCFG_MCID_MASK SQOSCFG_RCID_MASK
> +#define SQOSCFG_MCID_SHIFT 16
> +#define SQOSCFG_MASK ((SQOSCFG_MCID_MASK << SQOSCFG_MCID_SHIFT) | \
> + SQOSCFG_RCID_MASK)
> +
> /* Exception cause high bit - is an interrupt if set */
> #define CAUSE_IRQ_FLAG (_AC(1, UL) << (__riscv_xlen - 1))
>
> @@ -245,6 +252,7 @@
> #define CSR_STVAL 0x143
> #define CSR_SIP 0x144
> #define CSR_SATP 0x180
> +#define CSR_SQOSCFG 0x181
>
> #define CSR_STIMECMP 0x14D
> #define CSR_STIMECMPH 0x15D
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index 94a0590c6971..724b2aa2732d 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -39,6 +39,9 @@ struct thread_struct {
> unsigned long s[12]; /* s[0]: frame pointer */
> struct __riscv_d_ext_state fstate;
> unsigned long bad_cause;
> +#ifdef CONFIG_RISCV_ISA_SSQOSID
> + u32 sqoscfg;
> +#endif
> };
>
> /* Whitelist the fstate from the task_struct for hardened usercopy */
> diff --git a/arch/riscv/include/asm/qos.h b/arch/riscv/include/asm/qos.h
> new file mode 100644
> index 000000000000..297e7fb64d80
> --- /dev/null
> +++ b/arch/riscv/include/asm/qos.h
> @@ -0,0 +1,40 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_RISCV_QOS_H
> +#define _ASM_RISCV_QOS_H
> +
> +#ifdef CONFIG_RISCV_ISA_SSQOSID
> +
> +#include <linux/sched.h>
> +#include <linux/jump_label.h>
> +
> +#include <asm/barrier.h>
> +#include <asm/csr.h>
> +#include <asm/hwcap.h>
> +
> +/* cached value of sqoscfg csr for each cpu */
> +static DEFINE_PER_CPU(u32, cpu_sqoscfg);
> +
> +static void __qos_sched_in(struct task_struct *task)
> +{
> + u32 *cpu_sqoscfg_ptr = this_cpu_ptr(&cpu_sqoscfg);
> + u32 thread_sqoscfg;
> +
> + thread_sqoscfg = READ_ONCE(task->thread.sqoscfg);
> +
> + if (thread_sqoscfg != *cpu_sqoscfg_ptr) {
> + *cpu_sqoscfg_ptr = thread_sqoscfg;
> + csr_write(CSR_SQOSCFG, thread_sqoscfg);
> + }
> +}
> +
> +static inline void qos_sched_in(struct task_struct *task)
"qos" is a pretty generic prefix, no? Do you think we'd be better off
prefixing this (and every other extension related thing) with `riscv_`?
> +{
> + if (riscv_has_extension_likely(RISCV_ISA_EXT_SSQOSID))
> + __qos_sched_in(task);
> +}
> +#else
> +
> +static inline void qos_sched_in(struct task_struct *task) {}
> +
> +#endif /* CONFIG_RISCV_ISA_SSQOSID */
> +#endif /* _ASM_RISCV_QOS_H */
> diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
> index 60f8ca01d36e..75d9bfd766af 100644
> --- a/arch/riscv/include/asm/switch_to.h
> +++ b/arch/riscv/include/asm/switch_to.h
> @@ -12,6 +12,7 @@
> #include <asm/processor.h>
> #include <asm/ptrace.h>
> #include <asm/csr.h>
> +#include <asm/qos.h>
>
> #ifdef CONFIG_FPU
> extern void __fstate_save(struct task_struct *save_to);
> @@ -79,6 +80,7 @@ do { \
> if (has_fpu()) \
> __switch_to_aux(__prev, __next); \
> ((last) = __switch_to(__prev, __next)); \
> + qos_sched_in(__next); \
Both FPU and vector do:
| if (has_fpu()) \
| __switch_to_fpu(__prev, __next); \
| if (has_vector()) \
| __switch_to_vector(__prev, __next); \
Is it just my OCD that wants ssqosid to be the same?
It'd also do away with that seems a bit weird to me: having
qos_sched_in() and __qos_sched_in().
Even if you don't make them similar, what's the rationale behind not
inverting the extension check & returning early from a single function.
This is kinda above my pay grade, so let me know what I've inevitably
missed,
Conor.
>
> #endif /* _ASM_RISCV_SWITCH_TO_H */
> --
> 2.34.1
>
On Mon, Apr 17, 2023 at 08:10:20PM +0100, Conor Dooley wrote:
> Hey Drew,
>
> (Don't get your hopes up, I don't have anything really meaningful to
> contribute, sorry.)
Hi, thanks for the feedback...
>
> On Sun, Apr 09, 2023 at 09:36:46PM -0700, Drew Fustini wrote:
> > Add support for the sqoscfg CSR defined in the Ssqosid ISA extension
> > (Supervisor-mode Quality of Service ID). The CSR contains two fields:
> >
> > - Resource Control ID (RCID) used determine resource allocation
> > - Monitoring Counter ID (MCID) used to track resource usage
> >
> > Requests from a hart to shared resources like cache will be tagged with
> > these IDs. This allows the usage of shared resources to be associated
> > with the task currently running on the hart.
> >
> > A sqoscfg field is added to thread_struct and has the same format as the
> > sqoscfg CSR. This allows the scheduler to set the hart's sqoscfg CSR to
> > contain the RCID and MCID for the task that is being scheduled in. The
> > sqoscfg CSR is only written to if the thread_struct.sqoscfg is different
> > from the current value of the CSR.
> >
> > A per-cpu variable cpu_sqoscfg is used to mirror that state of the CSR.
> > This is because access to L1D hot memory should be several times faster
> > than a CSR read. Also, in the case of virtualization, accesses to this
> > CSR are trapped in the hypervisor.
> >
> > Link: https://github.com/riscv-non-isa/riscv-cmqri/blob/main/riscv-cbqri.pdf
> > Co-developed-by: Kornel Dulęba <[email protected]>
> > Signed-off-by: Kornel Dulęba <[email protected]>
> > Signed-off-by: Drew Fustini <[email protected]>
> > ---
> > Note: the Ssqosid extension and CBQRI spec are still in a draft state.
> > The CSR address of sqoscfg is not final.
> >
> > Changes from the original patch [1]:
> > - Rebase from 6.0 to 6.3
> > - Simplify per-cpu variable from struct to u32 with just sqoscfg
> > - Move qoscfg to thread_struct in arch/riscv/include/asm/processor.h
> > This avoids changing task_struct in /include/linux/sched.h
> > - Reword commit description
> > - Reword Kconfig description
> >
> > [1] https://github.com/rivosinc/linux/commit/8454b793a62be21d39e5826ef5241dfa06198ba9
> >
> > arch/riscv/Kconfig | 19 ++++++++++++++
> > arch/riscv/include/asm/csr.h | 8 ++++++
> > arch/riscv/include/asm/processor.h | 3 +++
> > arch/riscv/include/asm/qos.h | 40 ++++++++++++++++++++++++++++++
> > arch/riscv/include/asm/switch_to.h | 2 ++
> > 5 files changed, 72 insertions(+)
> > create mode 100644 arch/riscv/include/asm/qos.h
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index cc02eb9eee1f..03f22b7fe34b 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -418,6 +418,25 @@ config RISCV_ISA_SVNAPOT
> >
> > If you don't know what to do here, say Y.
> >
> > +config RISCV_ISA_SSQOSID
> > + bool "Ssqosid extension support"
> > + default y
> > + help
> > + Adds support for the Ssqosid ISA extension (Supervisor-mode
> > + Quality of Service ID).
>
> Could you add "long form" text in brackets here to the bool line, a la:
> https://patchwork.kernel.org/project/linux-riscv/patch/20230405-pucker-cogwheel-3a999a94a2f2@wendy/
Thanks, that is a good idea. It would make it easier for the person
using menuconfig as they won't have to access the help screen just to
see what the acronym stands for.
> > +
> > + Ssqosid defines the sqoscfg CSR which allows the system to tag
> > + the running process with RCID (Resource Control ID) and MCID
> > + (Monitoring Counter ID). The RCID is used determine resource
> > + allocation. The MCID is used to track resource usage in event
> > + counters.
> > +
> > + For example, a cache controller may use the RCID to apply a
> > + cache partitioning scheme and use the MCID to track how much
> > + cache a process, or a group of processes, is using.
> > +
> > + If you don't know what to do here, say Y.
> > +
> > config RISCV_ISA_SVPBMT
> > bool "SVPBMT extension support"
> > depends on 64BIT && MMU
> > diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> > index 7c2b8cdb7b77..17d04a0cacd6 100644
> > --- a/arch/riscv/include/asm/csr.h
> > +++ b/arch/riscv/include/asm/csr.h
> > @@ -59,6 +59,13 @@
> > #define SATP_ASID_MASK _AC(0xFFFF, UL)
> > #endif
> >
> > +/* SQOSCFG fields */
> > +#define SQOSCFG_RCID_MASK _AC(0x00000FFF, UL)
> > +#define SQOSCFG_MCID_MASK SQOSCFG_RCID_MASK
> > +#define SQOSCFG_MCID_SHIFT 16
> > +#define SQOSCFG_MASK ((SQOSCFG_MCID_MASK << SQOSCFG_MCID_SHIFT) | \
> > + SQOSCFG_RCID_MASK)
> > +
> > /* Exception cause high bit - is an interrupt if set */
> > #define CAUSE_IRQ_FLAG (_AC(1, UL) << (__riscv_xlen - 1))
> >
> > @@ -245,6 +252,7 @@
> > #define CSR_STVAL 0x143
> > #define CSR_SIP 0x144
> > #define CSR_SATP 0x180
> > +#define CSR_SQOSCFG 0x181
> >
> > #define CSR_STIMECMP 0x14D
> > #define CSR_STIMECMPH 0x15D
> > diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> > index 94a0590c6971..724b2aa2732d 100644
> > --- a/arch/riscv/include/asm/processor.h
> > +++ b/arch/riscv/include/asm/processor.h
> > @@ -39,6 +39,9 @@ struct thread_struct {
> > unsigned long s[12]; /* s[0]: frame pointer */
> > struct __riscv_d_ext_state fstate;
> > unsigned long bad_cause;
> > +#ifdef CONFIG_RISCV_ISA_SSQOSID
> > + u32 sqoscfg;
> > +#endif
> > };
> >
> > /* Whitelist the fstate from the task_struct for hardened usercopy */
> > diff --git a/arch/riscv/include/asm/qos.h b/arch/riscv/include/asm/qos.h
> > new file mode 100644
> > index 000000000000..297e7fb64d80
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/qos.h
> > @@ -0,0 +1,40 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef _ASM_RISCV_QOS_H
> > +#define _ASM_RISCV_QOS_H
> > +
> > +#ifdef CONFIG_RISCV_ISA_SSQOSID
> > +
> > +#include <linux/sched.h>
> > +#include <linux/jump_label.h>
> > +
> > +#include <asm/barrier.h>
> > +#include <asm/csr.h>
> > +#include <asm/hwcap.h>
> > +
> > +/* cached value of sqoscfg csr for each cpu */
> > +static DEFINE_PER_CPU(u32, cpu_sqoscfg);
> > +
> > +static void __qos_sched_in(struct task_struct *task)
> > +{
> > + u32 *cpu_sqoscfg_ptr = this_cpu_ptr(&cpu_sqoscfg);
> > + u32 thread_sqoscfg;
> > +
> > + thread_sqoscfg = READ_ONCE(task->thread.sqoscfg);
> > +
> > + if (thread_sqoscfg != *cpu_sqoscfg_ptr) {
> > + *cpu_sqoscfg_ptr = thread_sqoscfg;
> > + csr_write(CSR_SQOSCFG, thread_sqoscfg);
> > + }
> > +}
> > +
> > +static inline void qos_sched_in(struct task_struct *task)
>
> "qos" is a pretty generic prefix, no? Do you think we'd be better off
> prefixing this (and every other extension related thing) with `riscv_`?
That's a fair point. No harm in adding the 'riscv_' to make the context
clearer.
>
> > +{
> > + if (riscv_has_extension_likely(RISCV_ISA_EXT_SSQOSID))
> > + __qos_sched_in(task);
> > +}
> > +#else
> > +
> > +static inline void qos_sched_in(struct task_struct *task) {}
> > +
> > +#endif /* CONFIG_RISCV_ISA_SSQOSID */
> > +#endif /* _ASM_RISCV_QOS_H */
> > diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
> > index 60f8ca01d36e..75d9bfd766af 100644
> > --- a/arch/riscv/include/asm/switch_to.h
> > +++ b/arch/riscv/include/asm/switch_to.h
> > @@ -12,6 +12,7 @@
> > #include <asm/processor.h>
> > #include <asm/ptrace.h>
> > #include <asm/csr.h>
> > +#include <asm/qos.h>
> >
> > #ifdef CONFIG_FPU
> > extern void __fstate_save(struct task_struct *save_to);
> > @@ -79,6 +80,7 @@ do { \
> > if (has_fpu()) \
> > __switch_to_aux(__prev, __next); \
> > ((last) = __switch_to(__prev, __next)); \
> > + qos_sched_in(__next); \
>
> Both FPU and vector do:
> | if (has_fpu()) \
> | __switch_to_fpu(__prev, __next); \
> | if (has_vector()) \
> | __switch_to_vector(__prev, __next); \
>
> Is it just my OCD that wants ssqosid to be the same?
Thanks, I had not noticed those changes from the vector patch series [1]
until you pointed it out. The handling of sqoscfg could be converted to
that pattern too.
> It'd also do away with that seems a bit weird to me: having
> qos_sched_in() and __qos_sched_in().
> Even if you don't make them similar, what's the rationale behind not
> inverting the extension check & returning early from a single function.
The goal was so the inline qos_sched_in() would turn into a nop when
Ssqosid extensions not present. If Ssqosid was present, then the "real"
function __qos_sched_in() would be called.
However, having looked at the handling of fpu and vector in the vector
series, I think will redo the sqoscfg handling to follow that pattern.
thanks,
drew
[1] https://lore.kernel.org/linux-riscv/[email protected]/
On Mon, Apr 17, 2023 at 01:04:11PM -0700, Drew Fustini wrote:
> On Mon, Apr 17, 2023 at 08:10:20PM +0100, Conor Dooley wrote:
> > On Sun, Apr 09, 2023 at 09:36:46PM -0700, Drew Fustini wrote:
> > > #ifdef CONFIG_FPU
> > > extern void __fstate_save(struct task_struct *save_to);
> > > @@ -79,6 +80,7 @@ do { \
> > > if (has_fpu()) \
> > > __switch_to_aux(__prev, __next); \
> > > ((last) = __switch_to(__prev, __next)); \
> > > + qos_sched_in(__next); \
> >
> > Both FPU and vector do:
> > | if (has_fpu()) \
> > | __switch_to_fpu(__prev, __next); \
> > | if (has_vector()) \
> > | __switch_to_vector(__prev, __next); \
> >
> > Is it just my OCD that wants ssqosid to be the same?
>
> Thanks, I had not noticed those changes from the vector patch series [1]
> until you pointed it out. The handling of sqoscfg could be converted to
> that pattern too.
>
> > It'd also do away with that seems a bit weird to me: having
> > qos_sched_in() and __qos_sched_in().
> > Even if you don't make them similar, what's the rationale behind not
> > inverting the extension check & returning early from a single function.
>
> The goal was so the inline qos_sched_in() would turn into a nop when
> Ssqosid extensions not present. If Ssqosid was present, then the "real"
> function __qos_sched_in() would be called.
>
> However, having looked at the handling of fpu and vector in the vector
> series, I think will redo the sqoscfg handling to follow that pattern.
Aye. With the way they do it, if !CONFIG_..._SSQOSID, DCE should
remove the function call entirely & the has_extension_[un]likely() stuff
will give you your nop for kernels with CONFIG_..._SSQOSID but no
hardware support.
I think it looks "nicer"/more obvious if you copy what the fpu/vector
stuff does /shrug
Cheers,
Conor.