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[-next,v19,00/24] riscv: Add vector ISA support

Message ID 20230509103033.11285-1-andy.chiu@sifive.com (mailing list archive)
Headers show
Series riscv: Add vector ISA support | expand

Message

Andy Chiu May 9, 2023, 10:30 a.m. UTC 
This patchset is implemented based on vector 1.0 spec to add vector support
in riscv Linux kernel. There are some assumptions for this implementations.

1. We assume all harts has the same ISA in the system.
2. We disable vector in both kernel and user space [1] by default. Only
   enable an user's vector after an illegal instruction trap where it
   actually starts executing vector (the first-use trap [2]).
3. We detect "riscv,isa" to determine whether vector is support or not.

We defined a new structure __riscv_v_ext_state in struct thread_struct to
save/restore the vector related registers. It is used for both kernel space
and user space.
 - In kernel space, the datap pointer in __riscv_v_ext_state will be
   allocated to save vector registers.
 - In user space,
	- In signal handler of user space, the structure is placed
	  right after __riscv_ctx_hdr, which is embedded in fp reserved
	  aera. This is required to avoid ABI break [2]. And datap points
	  to the end of __riscv_v_ext_state.
	- In ptrace, the data will be put in ubuf in which we use
	  riscv_vr_get()/riscv_vr_set() to get or set the
	  __riscv_v_ext_state data structure from/to it, datap pointer
	  would be zeroed and vector registers will be copied to the
	  address right after the __riscv_v_ext_state structure in ubuf.

This patchset is rebased to v6.4-rc1 and it is tested by running several
vector programs simultaneously. It delivers signals correctly in a test
where we can see a valid ucontext_t in a signal handler, and a correct V
context returing back from it. And the ptrace interface is tested by
PTRACE_{GET,SET}REGSET. Lastly, KVM is tested by running above tests in
a guest using the same kernel image. All tests are done on an rv64gcv
virt QEMU.

Source tree:
https://github.com/sifive/riscv-linux/tree/riscv/for-next/vector-v19

Links:
 - [1] https://lore.kernel.org/all/20220921214439.1491510-17-stillson@rivosinc.com/
 - [2] https://lore.kernel.org/all/73c0124c-4794-6e40-460c-b26df407f322@rivosinc.com/T/#u
 - [3] https://lore.kernel.org/all/20230128082847.3055316-1-apatel@ventanamicro.com/

Updated patches: 6, 8, 14 (conflict), 15 (conflict), 19 (conflict), 23
New patches: 3, 20, 21, 24
Unchanged patches: 1, 2, 4, 5, 7, 9, 10, 11, 12, 13, 16, 17, 18, 22

---
Changelog V19
 - Rebase to the latest -next branch (at 6.4-rc1 ac9a786). Solve
   conflicts at patch 14, 15, and 19.
 - Add a sysctl, and prctl intefaces for userspace Vector control, and a
   document for it. (patch 20, 21, 24)
 - Add a Kconfig RISCV_V_DISABLE to set the default value of userspace
   Vector enablement status at compile-time. (patch 23)
 - Allow hwprobe interface to probe Vector. (patch 3)
 - Fix typos and commit msg at patch 6 and 8.

Changelog V18
 - Rebase to the latest -next branch (at 9c2598d)
 - patch 7: Detect inconsistent VLEN setup on an SMP system (Heiko).
 - patch 10: Add blank lines (Heiko)
 - patch 10: Return immediately in insn_is_vector() if an insn matches (Heiko)
 - patch 11: Use sizeof(vstate->datap) instead of sizeof(void*) (Eike)

Changelog V17
 - Rebase to the latest -next branch (at e45d6a5):
   - Solve conflicts at 9 and 13 due to generic entry
   - Use generic entry in do_trap_insn_illegal() trap handler

Changelog V16
 - Rebase to the latest for-next (at 4b74077):
 - Solve conflicts at 7, and 17
 - Use as-instr to detect if assembler supports .option arch directive
   and remove dependency from GAS, for both ZBB and V.
 - Cleanup code in KVM vector
 - Address issue reported by sparse
 - Refine code:
   - Fix a mixed-use of space/tab
   - Remove new lines at the end of file

Changelog V15
 - Rebase to risc-v -next (v6.3-rc1)
 - Make V depend on FD in Kconfig according to the spec and shut off v
   properly.
 - Fix a syntax error for clang build. But mark RISCV_ISA_V GAS only due
   to https://reviews.llvm.org/D123515
 - Use scratch reg in inline asm instead of t4.
 - Refine code.
 - Cleanup per-patch changelogs.

Changelog V14
 - Rebase to risc-v -next (v6.2-rc7)
 - Use TOOLCHAIN_HAS_V to detect if we can enable Vector. And refine
   KBUILD_CFLAGS to remove v from default compile option.
 - Drop illegal instruction handling patch in kvm and leave it to a
   independent series[3]. The series has merged into 6.3-rc1
 - Move KVM_RISCV_ISA_EXT_V to the end of enum to prevent potential ABI
   breaks.
 - Use PT_SIZE_ON_STACK instead of PT_SIZE to fit alignment. Also,
   remove panic log from v13 (15/19) because it is no longer relevant.
 - Rewrite insn_is_vector for better structuring (change if-else chain to
   a switch)
 - Fix compilation error in the middle of the series
 - Validate size of the alternative signal frame if V is enabled
   whenever:
     - The user call sigaltstack to update altstack
     - A signal is being delivered
 - Rename __riscv_v_state to __riscv_v_ext_state.
 - Add riscv_v_ prefix and rename rvv appropriately
 - Organize riscv_v_vsize setup code into vector.c
 - Address the issue mentioned by Heiko on !FPU case
 - Honor orignal authors that got changed accidentally in v13 4,5,6

Changelog V13
 - Rebase to latest risc-v next (v6.2-rc1)
 - vineetg: Re-organize the series to comply with bisect-ability
 - andy.chiu: Improve task switch with inline assembly
 - Re-structure the signal frame to avoid user ABI break.
 - Implemnt first-use trap and drop prctl for per-task V state
   enablement. Also, redirect this trap from hs to vs for kvm setup.
 - Do not expose V context in ptrace/sigframe until the task start using
   V. But still reserve V context for size ofsigframe reported by auxv.
 - Drop the kernel mode vector and leave it to another (future) series.

Changelog V12 (Chris)
 - rebases to some point after v5.18-rc6
 - add prctl to control per-process V state

Chnagelog V10
 - Rebase to v5.18-rc6
 - Merge several patches
 - Refine codes
 - Fix bugs
 - Add kvm vector support

Changelog V9
 - Rebase to v5.15
 - Merge several patches
 - Refine codes
 - Fix a kernel panic issue

Changelog V8
 - Rebase to v5.14
 - Refine struct __riscv_v_ext_state with struct __riscv_ctx_hdr
 - Refine has_vector into a static key
 - Defined __reserved space in struct sigcontext for vector and future extensions

Changelog V7
 - Add support for kernel mode vector
 - Add vector extension XOR implementation
 - Optimize task switch codes of vector
 - Allocate space for vector registers in start_thread()
 - Fix an illegal instruction exception when accessing vlenb
 - Optimize vector registers initialization
 - Initialize vector registers with proper vsetvli then it can work normally
 - Refine ptrace porting due to generic API changed
 - Code clean up

Changelog V6
 - Replace vle.v/vse.v instructions with vle8.v/vse8.v based on 0.9 spec
 - Add comments based on mailinglist feedback
 - Fix rv32 build error

Changelog V5
 - Using regset_size() correctly in generic ptrace
 - Fix the ptrace porting
 - Fix compile warning

Changelog V4
 - Support dynamic vlen
 - Fix bugs: lazy save/resotre, not saving vtype
 - Update VS bit offset based on latest vector spec
 - Add new vector csr based on latest vector spec
 - Code refine and removed unused macros

Changelog V3
 - Rebase linux-5.6-rc3 and tested with qemu
 - Seperate patches with Anup's advice
 - Give out a ABI puzzle with unlimited vlen

Changelog V2
 - Fixup typo "vecotr, fstate_save->vstate_save".
 - Fixup wrong saved registers' length in vector.S.
 - Seperate unrelated patches from this one.

Andy Chiu (8):
  riscv: hwprobe: Add support for RISCV_HWPROBE_BASE_BEHAVIOR_V
  riscv: Allocate user's vector context in the first-use trap
  riscv: signal: check fp-reserved words unconditionally
  riscv: signal: validate altstack to reflect Vector
  riscv: Add prctl controls for userspace vector management
  riscv: Add sysctl to set the default vector rule for new processes
  riscv: detect assembler support for .option arch
  riscv: Add documentation for Vector

Greentime Hu (9):
  riscv: Add new csr defines related to vector extension
  riscv: Clear vector regfile on bootup
  riscv: Introduce Vector enable/disable helpers
  riscv: Introduce riscv_v_vsize to record size of Vector context
  riscv: Introduce struct/helpers to save/restore per-task Vector state
  riscv: Add task switch support for vector
  riscv: Add ptrace vector support
  riscv: signal: Add sigcontext save/restore for vector
  riscv: prevent stack corruption by reserving task_pt_regs(p) early

Guo Ren (4):
  riscv: Rename __switch_to_aux() -> fpu
  riscv: Extending cpufeature.c to detect V-extension
  riscv: Disable Vector Instructions for kernel itself
  riscv: Enable Vector code to be built

Vincent Chen (3):
  riscv: signal: Report signal frame size to userspace via auxv
  riscv: kvm: Add V extension to KVM ISA
  riscv: KVM: Add vector lazy save/restore support

 Documentation/riscv/hwprobe.rst          |  10 +
 Documentation/riscv/index.rst            |   1 +
 Documentation/riscv/vector.rst           | 128 +++++++++++
 arch/riscv/Kconfig                       |  39 +++-
 arch/riscv/Makefile                      |   6 +-
 arch/riscv/include/asm/csr.h             |  18 +-
 arch/riscv/include/asm/elf.h             |   9 +
 arch/riscv/include/asm/hwcap.h           |   1 +
 arch/riscv/include/asm/hwprobe.h         |   2 +-
 arch/riscv/include/asm/insn.h            |  29 +++
 arch/riscv/include/asm/kvm_host.h        |   2 +
 arch/riscv/include/asm/kvm_vcpu_vector.h |  82 +++++++
 arch/riscv/include/asm/processor.h       |  16 ++
 arch/riscv/include/asm/switch_to.h       |   9 +-
 arch/riscv/include/asm/thread_info.h     |   3 +
 arch/riscv/include/asm/vector.h          | 184 ++++++++++++++++
 arch/riscv/include/uapi/asm/auxvec.h     |   1 +
 arch/riscv/include/uapi/asm/hwcap.h      |   1 +
 arch/riscv/include/uapi/asm/hwprobe.h    |   3 +
 arch/riscv/include/uapi/asm/kvm.h        |   8 +
 arch/riscv/include/uapi/asm/ptrace.h     |  39 ++++
 arch/riscv/include/uapi/asm/sigcontext.h |  16 +-
 arch/riscv/kernel/Makefile               |   1 +
 arch/riscv/kernel/cpufeature.c           |  13 ++
 arch/riscv/kernel/entry.S                |   6 +-
 arch/riscv/kernel/head.S                 |  41 +++-
 arch/riscv/kernel/process.c              |  19 ++
 arch/riscv/kernel/ptrace.c               |  70 ++++++
 arch/riscv/kernel/setup.c                |   3 +
 arch/riscv/kernel/signal.c               | 220 ++++++++++++++++---
 arch/riscv/kernel/smpboot.c              |   7 +
 arch/riscv/kernel/sys_riscv.c            |   9 +
 arch/riscv/kernel/traps.c                |  26 ++-
 arch/riscv/kernel/vector.c               | 266 +++++++++++++++++++++++
 arch/riscv/kvm/Makefile                  |   1 +
 arch/riscv/kvm/vcpu.c                    |  25 +++
 arch/riscv/kvm/vcpu_vector.c             | 186 ++++++++++++++++
 include/uapi/linux/elf.h                 |   1 +
 include/uapi/linux/prctl.h               |  11 +
 kernel/sys.c                             |  12 +
 40 files changed, 1474 insertions(+), 50 deletions(-)
 create mode 100644 Documentation/riscv/vector.rst
 create mode 100644 arch/riscv/include/asm/kvm_vcpu_vector.h
 create mode 100644 arch/riscv/include/asm/vector.h
 create mode 100644 arch/riscv/kernel/vector.c
 create mode 100644 arch/riscv/kvm/vcpu_vector.c

Comments

Heiko Stübner May 9, 2023, 11:14 a.m. UTC | #1 
Hi,

need to poke this more, but one issue popped up at first compile.

Am Dienstag, 9. Mai 2023, 12:30:29 CEST schrieb Andy Chiu:
> This patch add two riscv-specific prctls, to allow usespace control the
> use of vector unit:
> 
>  * PR_RISCV_V_SET_CONTROL: control the permission to use Vector at next,
>    or all following execve for a thread. Turning off a thread's Vector
>    live is not possible since libraries may have registered ifunc that
>    may execute Vector instructions.
>  * PR_RISCV_V_GET_CONTROL: get the same permission setting for the
>    current thread, and the setting for following execve(s).
> 
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
> Reviewed-by: Vincent Chen <vincent.chen@sifive.com>


> diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
> index 960a343799c6..16ccb35625a9 100644
> --- a/arch/riscv/kernel/vector.c
> +++ b/arch/riscv/kernel/vector.c
> @@ -9,6 +9,7 @@
>  #include <linux/slab.h>
>  #include <linux/sched.h>
>  #include <linux/uaccess.h>
> +#include <linux/prctl.h>
>  
>  #include <asm/thread_info.h>
>  #include <asm/processor.h>
> @@ -19,6 +20,8 @@
>  #include <asm/ptrace.h>
>  #include <asm/bug.h>
>  
> +static bool riscv_v_implicit_uacc = !IS_ENABLED(CONFIG_RISCV_V_DISABLE);
> +
>  unsigned long riscv_v_vsize __read_mostly;
>  EXPORT_SYMBOL_GPL(riscv_v_vsize);
>  
> @@ -91,11 +94,51 @@ static int riscv_v_thread_zalloc(void)
>  	return 0;
>  }
>  
> +#define VSTATE_CTRL_GET_CUR(x) ((x) & PR_RISCV_V_VSTATE_CTRL_CUR_MASK)
> +#define VSTATE_CTRL_GET_NEXT(x) (((x) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK) >> 2)
> +#define VSTATE_CTRL_MAKE_NEXT(x) (((x) << 2) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK)
> +#define VSTATE_CTRL_GET_INHERIT(x) (!!((x) & PR_RISCV_V_VSTATE_CTRL_INHERIT))
> +static inline int riscv_v_get_cur_ctrl(struct task_struct *tsk)
> +{
> +	return VSTATE_CTRL_GET_CUR(tsk->thread.vstate_ctrl);
> +}
> +
> +static inline int riscv_v_get_next_ctrl(struct task_struct *tsk)
> +{
> +	return VSTATE_CTRL_GET_NEXT(tsk->thread.vstate_ctrl);
> +}
> +
> +static inline bool riscv_v_test_ctrl_inherit(struct task_struct *tsk)
> +{
> +	return VSTATE_CTRL_GET_INHERIT(tsk->thread.vstate_ctrl);
> +}
> +
> +static inline void riscv_v_set_ctrl(struct task_struct *tsk, int cur, int nxt,
> +				    bool inherit)
> +{
> +	unsigned long ctrl;
> +
> +	ctrl = cur & PR_RISCV_V_VSTATE_CTRL_CUR_MASK;
> +	ctrl |= VSTATE_CTRL_MAKE_NEXT(nxt);
> +	if (inherit)
> +		ctrl |= PR_RISCV_V_VSTATE_CTRL_INHERIT;
> +	tsk->thread.vstate_ctrl = ctrl;
> +}
> +
> +bool riscv_v_user_allowed(void)
> +{
> +	return riscv_v_get_cur_ctrl(current) == PR_RISCV_V_VSTATE_CTRL_ON;
> +}

EXPORT_SYMBOL(riscv_v_user_allowed);

kvm is allowed to be built as module, so you could end up with:

ERROR: modpost: "riscv_v_user_allowed" [arch/riscv/kvm/kvm.ko] undefined!
make[2]: *** [../scripts/Makefile.modpost:136: Module.symvers] Fehler 1
make[1]: *** [/home/devel/hstuebner/00_git-repos/linux-riscv/Makefile:1978: modpost] Fehler 2
make[1]: Verzeichnis „/home/devel/hstuebner/00_git-repos/linux-riscv/_build-riscv64“ wird verlassen
make: *** [Makefile:226: __sub-make] Fehler 2


Heiko
Andy Chiu May 9, 2023, 4:11 p.m. UTC | #2 
On Tue, May 9, 2023 at 7:14 PM Heiko Stübner <heiko@sntech.de> wrote:
>
> Hi,
>
> need to poke this more, but one issue popped up at first compile.
>
> Am Dienstag, 9. Mai 2023, 12:30:29 CEST schrieb Andy Chiu:
> > This patch add two riscv-specific prctls, to allow usespace control the
> > use of vector unit:
> >
> >  * PR_RISCV_V_SET_CONTROL: control the permission to use Vector at next,
> >    or all following execve for a thread. Turning off a thread's Vector
> >    live is not possible since libraries may have registered ifunc that
> >    may execute Vector instructions.
> >  * PR_RISCV_V_GET_CONTROL: get the same permission setting for the
> >    current thread, and the setting for following execve(s).
> >
> > Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> > Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
> > Reviewed-by: Vincent Chen <vincent.chen@sifive.com>
>
>
> > diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
> > index 960a343799c6..16ccb35625a9 100644
> > --- a/arch/riscv/kernel/vector.c
> > +++ b/arch/riscv/kernel/vector.c
> > @@ -9,6 +9,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/sched.h>
> >  #include <linux/uaccess.h>
> > +#include <linux/prctl.h>
> >
> >  #include <asm/thread_info.h>
> >  #include <asm/processor.h>
> > @@ -19,6 +20,8 @@
> >  #include <asm/ptrace.h>
> >  #include <asm/bug.h>
> >
> > +static bool riscv_v_implicit_uacc = !IS_ENABLED(CONFIG_RISCV_V_DISABLE);
> > +
> >  unsigned long riscv_v_vsize __read_mostly;
> >  EXPORT_SYMBOL_GPL(riscv_v_vsize);
> >
> > @@ -91,11 +94,51 @@ static int riscv_v_thread_zalloc(void)
> >       return 0;
> >  }
> >
> > +#define VSTATE_CTRL_GET_CUR(x) ((x) & PR_RISCV_V_VSTATE_CTRL_CUR_MASK)
> > +#define VSTATE_CTRL_GET_NEXT(x) (((x) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK) >> 2)
> > +#define VSTATE_CTRL_MAKE_NEXT(x) (((x) << 2) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK)
> > +#define VSTATE_CTRL_GET_INHERIT(x) (!!((x) & PR_RISCV_V_VSTATE_CTRL_INHERIT))
> > +static inline int riscv_v_get_cur_ctrl(struct task_struct *tsk)
> > +{
> > +     return VSTATE_CTRL_GET_CUR(tsk->thread.vstate_ctrl);
> > +}
> > +
> > +static inline int riscv_v_get_next_ctrl(struct task_struct *tsk)
> > +{
> > +     return VSTATE_CTRL_GET_NEXT(tsk->thread.vstate_ctrl);
> > +}
> > +
> > +static inline bool riscv_v_test_ctrl_inherit(struct task_struct *tsk)
> > +{
> > +     return VSTATE_CTRL_GET_INHERIT(tsk->thread.vstate_ctrl);
> > +}
> > +
> > +static inline void riscv_v_set_ctrl(struct task_struct *tsk, int cur, int nxt,
> > +                                 bool inherit)
> > +{
> > +     unsigned long ctrl;
> > +
> > +     ctrl = cur & PR_RISCV_V_VSTATE_CTRL_CUR_MASK;
> > +     ctrl |= VSTATE_CTRL_MAKE_NEXT(nxt);
> > +     if (inherit)
> > +             ctrl |= PR_RISCV_V_VSTATE_CTRL_INHERIT;
> > +     tsk->thread.vstate_ctrl = ctrl;
> > +}
> > +
> > +bool riscv_v_user_allowed(void)
> > +{
> > +     return riscv_v_get_cur_ctrl(current) == PR_RISCV_V_VSTATE_CTRL_ON;
> > +}
>
> EXPORT_SYMBOL(riscv_v_user_allowed);

It's a shame. KVM is a builtin on my test platform so I missed this
obvious thing. Or, maybe we should make them inline functions or
macros at the header file because of the size. And because other
modules may rarely use them.

>
> kvm is allowed to be built as module, so you could end up with:
>
> ERROR: modpost: "riscv_v_user_allowed" [arch/riscv/kvm/kvm.ko] undefined!
> make[2]: *** [../scripts/Makefile.modpost:136: Module.symvers] Fehler 1
> make[1]: *** [/home/devel/hstuebner/00_git-repos/linux-riscv/Makefile:1978: modpost] Fehler 2
> make[1]: Verzeichnis „/home/devel/hstuebner/00_git-repos/linux-riscv/_build-riscv64“ wird verlassen
> make: *** [Makefile:226: __sub-make] Fehler 2
>
>
> Heiko
>
>
>

Thanks,
Andy
Palmer Dabbelt May 9, 2023, 5:58 p.m. UTC | #3 
On Tue, 09 May 2023 04:14:26 PDT (-0700), heiko@sntech.de wrote:
> Hi,
>
> need to poke this more, but one issue popped up at first compile.
>
> Am Dienstag, 9. Mai 2023, 12:30:29 CEST schrieb Andy Chiu:
>> This patch add two riscv-specific prctls, to allow usespace control the
>> use of vector unit:
>>
>>  * PR_RISCV_V_SET_CONTROL: control the permission to use Vector at next,
>>    or all following execve for a thread. Turning off a thread's Vector
>>    live is not possible since libraries may have registered ifunc that
>>    may execute Vector instructions.
>>  * PR_RISCV_V_GET_CONTROL: get the same permission setting for the
>>    current thread, and the setting for following execve(s).
>>
>> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
>> Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
>> Reviewed-by: Vincent Chen <vincent.chen@sifive.com>
>
>
>> diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
>> index 960a343799c6..16ccb35625a9 100644
>> --- a/arch/riscv/kernel/vector.c
>> +++ b/arch/riscv/kernel/vector.c
>> @@ -9,6 +9,7 @@
>>  #include <linux/slab.h>
>>  #include <linux/sched.h>
>>  #include <linux/uaccess.h>
>> +#include <linux/prctl.h>
>>
>>  #include <asm/thread_info.h>
>>  #include <asm/processor.h>
>> @@ -19,6 +20,8 @@
>>  #include <asm/ptrace.h>
>>  #include <asm/bug.h>
>>
>> +static bool riscv_v_implicit_uacc = !IS_ENABLED(CONFIG_RISCV_V_DISABLE);
>> +
>>  unsigned long riscv_v_vsize __read_mostly;
>>  EXPORT_SYMBOL_GPL(riscv_v_vsize);
>>
>> @@ -91,11 +94,51 @@ static int riscv_v_thread_zalloc(void)
>>  	return 0;
>>  }
>>
>> +#define VSTATE_CTRL_GET_CUR(x) ((x) & PR_RISCV_V_VSTATE_CTRL_CUR_MASK)
>> +#define VSTATE_CTRL_GET_NEXT(x) (((x) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK) >> 2)
>> +#define VSTATE_CTRL_MAKE_NEXT(x) (((x) << 2) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK)
>> +#define VSTATE_CTRL_GET_INHERIT(x) (!!((x) & PR_RISCV_V_VSTATE_CTRL_INHERIT))
>> +static inline int riscv_v_get_cur_ctrl(struct task_struct *tsk)
>> +{
>> +	return VSTATE_CTRL_GET_CUR(tsk->thread.vstate_ctrl);
>> +}
>> +
>> +static inline int riscv_v_get_next_ctrl(struct task_struct *tsk)
>> +{
>> +	return VSTATE_CTRL_GET_NEXT(tsk->thread.vstate_ctrl);
>> +}
>> +
>> +static inline bool riscv_v_test_ctrl_inherit(struct task_struct *tsk)
>> +{
>> +	return VSTATE_CTRL_GET_INHERIT(tsk->thread.vstate_ctrl);
>> +}
>> +
>> +static inline void riscv_v_set_ctrl(struct task_struct *tsk, int cur, int nxt,
>> +				    bool inherit)
>> +{
>> +	unsigned long ctrl;
>> +
>> +	ctrl = cur & PR_RISCV_V_VSTATE_CTRL_CUR_MASK;
>> +	ctrl |= VSTATE_CTRL_MAKE_NEXT(nxt);
>> +	if (inherit)
>> +		ctrl |= PR_RISCV_V_VSTATE_CTRL_INHERIT;
>> +	tsk->thread.vstate_ctrl = ctrl;
>> +}
>> +
>> +bool riscv_v_user_allowed(void)
>> +{
>> +	return riscv_v_get_cur_ctrl(current) == PR_RISCV_V_VSTATE_CTRL_ON;
>> +}
>
> EXPORT_SYMBOL(riscv_v_user_allowed);
>
> kvm is allowed to be built as module, so you could end up with:
>
> ERROR: modpost: "riscv_v_user_allowed" [arch/riscv/kvm/kvm.ko] undefined!
> make[2]: *** [../scripts/Makefile.modpost:136: Module.symvers] Fehler 1
> make[1]: *** [/home/devel/hstuebner/00_git-repos/linux-riscv/Makefile:1978: modpost] Fehler 2
> make[1]: Verzeichnis „/home/devel/hstuebner/00_git-repos/linux-riscv/_build-riscv64“ wird verlassen
> make: *** [Makefile:226: __sub-make] Fehler 2

and presumably that means that "make allmodconfig" hasn't been run, 
which might shake out some more issues.

>
>
> Heiko
Palmer Dabbelt May 9, 2023, 8:59 p.m. UTC | #4 
On Tue, 09 May 2023 03:30:09 PDT (-0700), andy.chiu@sifive.com wrote:
> This patchset is implemented based on vector 1.0 spec to add vector support
> in riscv Linux kernel. There are some assumptions for this implementations.
>
> 1. We assume all harts has the same ISA in the system.
> 2. We disable vector in both kernel and user space [1] by default. Only
>    enable an user's vector after an illegal instruction trap where it
>    actually starts executing vector (the first-use trap [2]).
> 3. We detect "riscv,isa" to determine whether vector is support or not.
>
> We defined a new structure __riscv_v_ext_state in struct thread_struct to
> save/restore the vector related registers. It is used for both kernel space
> and user space.
>  - In kernel space, the datap pointer in __riscv_v_ext_state will be
>    allocated to save vector registers.
>  - In user space,
> 	- In signal handler of user space, the structure is placed
> 	  right after __riscv_ctx_hdr, which is embedded in fp reserved
> 	  aera. This is required to avoid ABI break [2]. And datap points
> 	  to the end of __riscv_v_ext_state.
> 	- In ptrace, the data will be put in ubuf in which we use
> 	  riscv_vr_get()/riscv_vr_set() to get or set the
> 	  __riscv_v_ext_state data structure from/to it, datap pointer
> 	  would be zeroed and vector registers will be copied to the
> 	  address right after the __riscv_v_ext_state structure in ubuf.
>
> This patchset is rebased to v6.4-rc1 and it is tested by running several
> vector programs simultaneously. It delivers signals correctly in a test
> where we can see a valid ucontext_t in a signal handler, and a correct V
> context returing back from it. And the ptrace interface is tested by
> PTRACE_{GET,SET}REGSET. Lastly, KVM is tested by running above tests in
> a guest using the same kernel image. All tests are done on an rv64gcv
> virt QEMU.

Thanks for handling these.  Looks like there's some minor comments 
already, with at least the hwprobe issue being a proper bug.  I'll try 
to take a look through the rest of this ASAP, with any luck we can get 
this into linux-next early in the cycle.

>
> Source tree:
> https://github.com/sifive/riscv-linux/tree/riscv/for-next/vector-v19
>
> Links:
>  - [1] https://lore.kernel.org/all/20220921214439.1491510-17-stillson@rivosinc.com/
>  - [2] https://lore.kernel.org/all/73c0124c-4794-6e40-460c-b26df407f322@rivosinc.com/T/#u
>  - [3] https://lore.kernel.org/all/20230128082847.3055316-1-apatel@ventanamicro.com/
>
> Updated patches: 6, 8, 14 (conflict), 15 (conflict), 19 (conflict), 23
> New patches: 3, 20, 21, 24
> Unchanged patches: 1, 2, 4, 5, 7, 9, 10, 11, 12, 13, 16, 17, 18, 22
>
> ---
> Changelog V19
>  - Rebase to the latest -next branch (at 6.4-rc1 ac9a786). Solve
>    conflicts at patch 14, 15, and 19.
>  - Add a sysctl, and prctl intefaces for userspace Vector control, and a
>    document for it. (patch 20, 21, 24)
>  - Add a Kconfig RISCV_V_DISABLE to set the default value of userspace
>    Vector enablement status at compile-time. (patch 23)
>  - Allow hwprobe interface to probe Vector. (patch 3)
>  - Fix typos and commit msg at patch 6 and 8.
>
> Changelog V18
>  - Rebase to the latest -next branch (at 9c2598d)
>  - patch 7: Detect inconsistent VLEN setup on an SMP system (Heiko).
>  - patch 10: Add blank lines (Heiko)
>  - patch 10: Return immediately in insn_is_vector() if an insn matches (Heiko)
>  - patch 11: Use sizeof(vstate->datap) instead of sizeof(void*) (Eike)
>
> Changelog V17
>  - Rebase to the latest -next branch (at e45d6a5):
>    - Solve conflicts at 9 and 13 due to generic entry
>    - Use generic entry in do_trap_insn_illegal() trap handler
>
> Changelog V16
>  - Rebase to the latest for-next (at 4b74077):
>  - Solve conflicts at 7, and 17
>  - Use as-instr to detect if assembler supports .option arch directive
>    and remove dependency from GAS, for both ZBB and V.
>  - Cleanup code in KVM vector
>  - Address issue reported by sparse
>  - Refine code:
>    - Fix a mixed-use of space/tab
>    - Remove new lines at the end of file
>
> Changelog V15
>  - Rebase to risc-v -next (v6.3-rc1)
>  - Make V depend on FD in Kconfig according to the spec and shut off v
>    properly.
>  - Fix a syntax error for clang build. But mark RISCV_ISA_V GAS only due
>    to https://reviews.llvm.org/D123515
>  - Use scratch reg in inline asm instead of t4.
>  - Refine code.
>  - Cleanup per-patch changelogs.
>
> Changelog V14
>  - Rebase to risc-v -next (v6.2-rc7)
>  - Use TOOLCHAIN_HAS_V to detect if we can enable Vector. And refine
>    KBUILD_CFLAGS to remove v from default compile option.
>  - Drop illegal instruction handling patch in kvm and leave it to a
>    independent series[3]. The series has merged into 6.3-rc1
>  - Move KVM_RISCV_ISA_EXT_V to the end of enum to prevent potential ABI
>    breaks.
>  - Use PT_SIZE_ON_STACK instead of PT_SIZE to fit alignment. Also,
>    remove panic log from v13 (15/19) because it is no longer relevant.
>  - Rewrite insn_is_vector for better structuring (change if-else chain to
>    a switch)
>  - Fix compilation error in the middle of the series
>  - Validate size of the alternative signal frame if V is enabled
>    whenever:
>      - The user call sigaltstack to update altstack
>      - A signal is being delivered
>  - Rename __riscv_v_state to __riscv_v_ext_state.
>  - Add riscv_v_ prefix and rename rvv appropriately
>  - Organize riscv_v_vsize setup code into vector.c
>  - Address the issue mentioned by Heiko on !FPU case
>  - Honor orignal authors that got changed accidentally in v13 4,5,6
>
> Changelog V13
>  - Rebase to latest risc-v next (v6.2-rc1)
>  - vineetg: Re-organize the series to comply with bisect-ability
>  - andy.chiu: Improve task switch with inline assembly
>  - Re-structure the signal frame to avoid user ABI break.
>  - Implemnt first-use trap and drop prctl for per-task V state
>    enablement. Also, redirect this trap from hs to vs for kvm setup.
>  - Do not expose V context in ptrace/sigframe until the task start using
>    V. But still reserve V context for size ofsigframe reported by auxv.
>  - Drop the kernel mode vector and leave it to another (future) series.
>
> Changelog V12 (Chris)
>  - rebases to some point after v5.18-rc6
>  - add prctl to control per-process V state
>
> Chnagelog V10
>  - Rebase to v5.18-rc6
>  - Merge several patches
>  - Refine codes
>  - Fix bugs
>  - Add kvm vector support
>
> Changelog V9
>  - Rebase to v5.15
>  - Merge several patches
>  - Refine codes
>  - Fix a kernel panic issue
>
> Changelog V8
>  - Rebase to v5.14
>  - Refine struct __riscv_v_ext_state with struct __riscv_ctx_hdr
>  - Refine has_vector into a static key
>  - Defined __reserved space in struct sigcontext for vector and future extensions
>
> Changelog V7
>  - Add support for kernel mode vector
>  - Add vector extension XOR implementation
>  - Optimize task switch codes of vector
>  - Allocate space for vector registers in start_thread()
>  - Fix an illegal instruction exception when accessing vlenb
>  - Optimize vector registers initialization
>  - Initialize vector registers with proper vsetvli then it can work normally
>  - Refine ptrace porting due to generic API changed
>  - Code clean up
>
> Changelog V6
>  - Replace vle.v/vse.v instructions with vle8.v/vse8.v based on 0.9 spec
>  - Add comments based on mailinglist feedback
>  - Fix rv32 build error
>
> Changelog V5
>  - Using regset_size() correctly in generic ptrace
>  - Fix the ptrace porting
>  - Fix compile warning
>
> Changelog V4
>  - Support dynamic vlen
>  - Fix bugs: lazy save/resotre, not saving vtype
>  - Update VS bit offset based on latest vector spec
>  - Add new vector csr based on latest vector spec
>  - Code refine and removed unused macros
>
> Changelog V3
>  - Rebase linux-5.6-rc3 and tested with qemu
>  - Seperate patches with Anup's advice
>  - Give out a ABI puzzle with unlimited vlen
>
> Changelog V2
>  - Fixup typo "vecotr, fstate_save->vstate_save".
>  - Fixup wrong saved registers' length in vector.S.
>  - Seperate unrelated patches from this one.
>
> Andy Chiu (8):
>   riscv: hwprobe: Add support for RISCV_HWPROBE_BASE_BEHAVIOR_V
>   riscv: Allocate user's vector context in the first-use trap
>   riscv: signal: check fp-reserved words unconditionally
>   riscv: signal: validate altstack to reflect Vector
>   riscv: Add prctl controls for userspace vector management
>   riscv: Add sysctl to set the default vector rule for new processes
>   riscv: detect assembler support for .option arch
>   riscv: Add documentation for Vector
>
> Greentime Hu (9):
>   riscv: Add new csr defines related to vector extension
>   riscv: Clear vector regfile on bootup
>   riscv: Introduce Vector enable/disable helpers
>   riscv: Introduce riscv_v_vsize to record size of Vector context
>   riscv: Introduce struct/helpers to save/restore per-task Vector state
>   riscv: Add task switch support for vector
>   riscv: Add ptrace vector support
>   riscv: signal: Add sigcontext save/restore for vector
>   riscv: prevent stack corruption by reserving task_pt_regs(p) early
>
> Guo Ren (4):
>   riscv: Rename __switch_to_aux() -> fpu
>   riscv: Extending cpufeature.c to detect V-extension
>   riscv: Disable Vector Instructions for kernel itself
>   riscv: Enable Vector code to be built
>
> Vincent Chen (3):
>   riscv: signal: Report signal frame size to userspace via auxv
>   riscv: kvm: Add V extension to KVM ISA
>   riscv: KVM: Add vector lazy save/restore support
>
>  Documentation/riscv/hwprobe.rst          |  10 +
>  Documentation/riscv/index.rst            |   1 +
>  Documentation/riscv/vector.rst           | 128 +++++++++++
>  arch/riscv/Kconfig                       |  39 +++-
>  arch/riscv/Makefile                      |   6 +-
>  arch/riscv/include/asm/csr.h             |  18 +-
>  arch/riscv/include/asm/elf.h             |   9 +
>  arch/riscv/include/asm/hwcap.h           |   1 +
>  arch/riscv/include/asm/hwprobe.h         |   2 +-
>  arch/riscv/include/asm/insn.h            |  29 +++
>  arch/riscv/include/asm/kvm_host.h        |   2 +
>  arch/riscv/include/asm/kvm_vcpu_vector.h |  82 +++++++
>  arch/riscv/include/asm/processor.h       |  16 ++
>  arch/riscv/include/asm/switch_to.h       |   9 +-
>  arch/riscv/include/asm/thread_info.h     |   3 +
>  arch/riscv/include/asm/vector.h          | 184 ++++++++++++++++
>  arch/riscv/include/uapi/asm/auxvec.h     |   1 +
>  arch/riscv/include/uapi/asm/hwcap.h      |   1 +
>  arch/riscv/include/uapi/asm/hwprobe.h    |   3 +
>  arch/riscv/include/uapi/asm/kvm.h        |   8 +
>  arch/riscv/include/uapi/asm/ptrace.h     |  39 ++++
>  arch/riscv/include/uapi/asm/sigcontext.h |  16 +-
>  arch/riscv/kernel/Makefile               |   1 +
>  arch/riscv/kernel/cpufeature.c           |  13 ++
>  arch/riscv/kernel/entry.S                |   6 +-
>  arch/riscv/kernel/head.S                 |  41 +++-
>  arch/riscv/kernel/process.c              |  19 ++
>  arch/riscv/kernel/ptrace.c               |  70 ++++++
>  arch/riscv/kernel/setup.c                |   3 +
>  arch/riscv/kernel/signal.c               | 220 ++++++++++++++++---
>  arch/riscv/kernel/smpboot.c              |   7 +
>  arch/riscv/kernel/sys_riscv.c            |   9 +
>  arch/riscv/kernel/traps.c                |  26 ++-
>  arch/riscv/kernel/vector.c               | 266 +++++++++++++++++++++++
>  arch/riscv/kvm/Makefile                  |   1 +
>  arch/riscv/kvm/vcpu.c                    |  25 +++
>  arch/riscv/kvm/vcpu_vector.c             | 186 ++++++++++++++++
>  include/uapi/linux/elf.h                 |   1 +
>  include/uapi/linux/prctl.h               |  11 +
>  kernel/sys.c                             |  12 +
>  40 files changed, 1474 insertions(+), 50 deletions(-)
>  create mode 100644 Documentation/riscv/vector.rst
>  create mode 100644 arch/riscv/include/asm/kvm_vcpu_vector.h
>  create mode 100644 arch/riscv/include/asm/vector.h
>  create mode 100644 arch/riscv/kernel/vector.c
>  create mode 100644 arch/riscv/kvm/vcpu_vector.c