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Message-ID: <20240423-headsman-arrival-16a2d13342b2@spud>
Date: Tue, 23 Apr 2024 17:39:27 +0100
From: Conor Dooley <conor@...nel.org>
To: Clément Léger <cleger@...osinc.com>
Cc: Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>, Anup Patel <anup@...infault.org>,
Atish Patra <atishp@...shpatra.org>,
linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
kvm-riscv@...ts.infradead.org, Ved Shanbhogue <ved@...osinc.com>
Subject: Re: [RFC PATCH 5/7] riscv: add double trap driver
On Thu, Apr 18, 2024 at 04:26:44PM +0200, Clément Léger wrote:
> Add a small driver to request double trap enabling as well as
> registering a SSE handler for double trap. This will also be used by KVM
> SBI FWFT extension support to detect if it is possible to enable double
> trap in VS-mode.
>
> Signed-off-by: Clément Léger <cleger@...osinc.com>
> ---
> arch/riscv/include/asm/sbi.h | 1 +
> drivers/firmware/Kconfig | 7 +++
> drivers/firmware/Makefile | 1 +
> drivers/firmware/riscv_dbltrp.c | 95 +++++++++++++++++++++++++++++++++
> include/linux/riscv_dbltrp.h | 19 +++++++
> 5 files changed, 123 insertions(+)
> create mode 100644 drivers/firmware/riscv_dbltrp.c
> create mode 100644 include/linux/riscv_dbltrp.h
>
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 744aa1796c92..9cd4ca66487c 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -314,6 +314,7 @@ enum sbi_sse_attr_id {
> #define SBI_SSE_ATTR_INTERRUPTED_FLAGS_SPIE (1 << 2)
>
> #define SBI_SSE_EVENT_LOCAL_RAS 0x00000000
> +#define SBI_SSE_EVENT_LOCAL_DOUBLE_TRAP 0x00000001
> #define SBI_SSE_EVENT_GLOBAL_RAS 0x00008000
> #define SBI_SSE_EVENT_LOCAL_PMU 0x00010000
> #define SBI_SSE_EVENT_LOCAL_SOFTWARE 0xffff0000
> diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
> index 59f611288807..a037f6e89942 100644
> --- a/drivers/firmware/Kconfig
> +++ b/drivers/firmware/Kconfig
> @@ -197,6 +197,13 @@ config RISCV_SSE_TEST
> Select if you want to enable SSE extension testing at boot time.
> This will run a series of test which verifies SSE sanity.
>
> +config RISCV_DBLTRP
> + bool "Enable Double trap handling"
> + depends on RISCV_SSE && RISCV_SBI
> + default n
> + help
> + Select if you want to enable SSE double trap handler.
> +
> config SYSFB
> bool
> select BOOT_VESA_SUPPORT
> diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> index fb7b0c08c56d..ad67a1738c0f 100644
> --- a/drivers/firmware/Makefile
> +++ b/drivers/firmware/Makefile
> @@ -18,6 +18,7 @@ obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
> obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
> obj-$(CONFIG_RISCV_SSE) += riscv_sse.o
> obj-$(CONFIG_RISCV_SSE_TEST) += riscv_sse_test.o
> +obj-$(CONFIG_RISCV_DBLTRP) += riscv_dbltrp.o
As previously mentioned, I'd like to see all of these riscv specific
things in a riscv directory.
> obj-$(CONFIG_SYSFB) += sysfb.o
> obj-$(CONFIG_SYSFB_SIMPLEFB) += sysfb_simplefb.o
> obj-$(CONFIG_TI_SCI_PROTOCOL) += ti_sci.o
> diff --git a/drivers/firmware/riscv_dbltrp.c b/drivers/firmware/riscv_dbltrp.c
> new file mode 100644
> index 000000000000..72f9a067e87a
> --- /dev/null
> +++ b/drivers/firmware/riscv_dbltrp.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2023 Rivos Inc.
> + */
> +
> +#define pr_fmt(fmt) "riscv-dbltrp: " fmt
> +
> +#include <linux/cpu.h>
> +#include <linux/init.h>
> +#include <linux/riscv_dbltrp.h>
> +#include <linux/riscv_sse.h>
> +
> +#include <asm/sbi.h>
> +
> +static bool double_trap_enabled;
> +
> +static int riscv_sse_dbltrp_handle(uint32_t evt, void *arg,
> + struct pt_regs *regs)
> +{
> + __show_regs(regs);
> + panic("Double trap !\n");
> +
> + return 0;
> +}
> +
> +struct cpu_dbltrp_data {
> + int error;
> +};
> +
> +static void
> +sbi_cpu_enable_double_trap(void *data)
This should easily fit on one line.
> +{
> + struct sbiret ret;
> + struct cpu_dbltrp_data *cdd = data;
> +
> + ret = sbi_ecall(SBI_EXT_FWFT, SBI_EXT_FWFT_SET,
> + SBI_FWFT_DOUBLE_TRAP_ENABLE, 1, 0, 0, 0, 0);
> +
> + if (ret.error) {
> + cdd->error = 1;
If this is a boolean, make it a boolean please. All the code in this
patch treats it as one.
> + pr_err("Failed to enable double trap on cpu %d\n", smp_processor_id());
> + }
> +}
> +
> +static int sbi_enable_double_trap(void)
> +{
> + struct cpu_dbltrp_data cdd = {0};
> +
> + on_each_cpu(sbi_cpu_enable_double_trap, &cdd, 1);
> + if (cdd.error)
> + return -1;
Can this be an errno please?
> +
> + double_trap_enabled = true;
> +
> + return 0;
> +}
> +
> +bool riscv_double_trap_enabled(void)
> +{
> + return double_trap_enabled;
> +}
> +EXPORT_SYMBOL(riscv_double_trap_enabled);
Can we just use double_trap everywhere? dbltrp reads like sound that a
beatboxer would make and this looks a lot nicer than the other functions
in the file...
> +
> +static int __init riscv_dbltrp(void)
I think this function is missing an action work - init or probe?
> +{
> + struct sse_event *evt;
> +
> + if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SSDBLTRP)) {
> + pr_err("Ssdbltrp extension not available\n");
> + return 1;
> + }
> +
> + if (!sbi_probe_extension(SBI_EXT_FWFT)) {
> + pr_err("Can not enable double trap, SBI_EXT_FWFT is not available\n");
> + return 1;
> + }
> +
> + if (sbi_enable_double_trap()) {
> + pr_err("Failed to enable double trap on all cpus\n");
> + return 1;
Why do we return 1s here, but an errno via PTR_ERR() below?
Shouldn't all of these be returning a negative errono?
This particular one should probably propagate the error it got from
sbi_enable_double_trap().
Cheers,
Conor.
> + }
> +
> + evt = sse_event_register(SBI_SSE_EVENT_LOCAL_DOUBLE_TRAP, 0,
> + riscv_sse_dbltrp_handle, NULL);
> + if (IS_ERR(evt)) {
> + pr_err("SSE double trap register failed\n");
> + return PTR_ERR(evt);
> + }
> +
> + sse_event_enable(evt);
> + pr_info("Double trap handling registered\n");
> +
> + return 0;
> +}
> +device_initcall(riscv_dbltrp);
> diff --git a/include/linux/riscv_dbltrp.h b/include/linux/riscv_dbltrp.h
> new file mode 100644
> index 000000000000..6de4f43fae6b
> --- /dev/null
> +++ b/include/linux/riscv_dbltrp.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2023 Rivos Inc.
> + */
> +
> +#ifndef __LINUX_RISCV_DBLTRP_H
> +#define __LINUX_RISCV_DBLTRP_H
> +
> +#if defined(CONFIG_RISCV_DBLTRP)
> +bool riscv_double_trap_enabled(void);
> +#else
> +
> +static inline bool riscv_double_trap_enabled(void)
> +{
> + return false;
> +}
> +#endif
> +
> +#endif /* __LINUX_RISCV_DBLTRP_H */
> --
> 2.43.0
>
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