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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Tue, 5 Mar 2024 21:15:25 +0100
Message-ID: <CAJZ5v0hTmkB_rrFgxUYbrxbs_JC-vM1oYdH27D-QvVaVuovNXg@mail.gmail.com>
Subject: Re: [PATCH v3] acpi: Use access_width over bit_width for system
 memory accesses
To: Jarred White <jarredwhite@linux.microsoft.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Len Brown <lenb@kernel.org>, 
	"open list:ACPI" <linux-acpi@vger.kernel.org>, open list <linux-kernel@vger.kernel.org>, 
	srivatsabhat@linux.microsoft.com, stable@vger.kernel.org
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On Fri, Mar 1, 2024 at 8:27=E2=80=AFPM Jarred White
<jarredwhite@linux.microsoft.com> wrote:
>
> To align with ACPI 6.3+, since bit_width can be any 8-bit value, we canno=
t
> depend on it being always on a clean 8b boundary. This was uncovered on t=
he
> Cobalt 100 platform.
>
> SError Interrupt on CPU26, code 0xbe000011 -- SError
>  CPU: 26 PID: 1510 Comm: systemd-udevd Not tainted 5.15.2.1-13 #1
>  Hardware name: MICROSOFT CORPORATION, BIOS MICROSOFT CORPORATION
>  pstate: 62400009 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=3D--)
>  pc : cppc_get_perf_caps+0xec/0x410
>  lr : cppc_get_perf_caps+0xe8/0x410
>  sp : ffff8000155ab730
>  x29: ffff8000155ab730 x28: ffff0080139d0038 x27: ffff0080139d0078
>  x26: 0000000000000000 x25: ffff0080139d0058 x24: 00000000ffffffff
>  x23: ffff0080139d0298 x22: ffff0080139d0278 x21: 0000000000000000
>  x20: ffff00802b251910 x19: ffff0080139d0000 x18: ffffffffffffffff
>  x17: 0000000000000000 x16: ffffdc7e111bad04 x15: ffff00802b251008
>  x14: ffffffffffffffff x13: ffff013f1fd63300 x12: 0000000000000006
>  x11: ffffdc7e128f4420 x10: 0000000000000000 x9 : ffffdc7e111badec
>  x8 : ffff00802b251980 x7 : 0000000000000000 x6 : ffff0080139d0028
>  x5 : 0000000000000000 x4 : ffff0080139d0018 x3 : 00000000ffffffff
>  x2 : 0000000000000008 x1 : ffff8000155ab7a0 x0 : 0000000000000000
>  Kernel panic - not syncing: Asynchronous SError Interrupt
>  CPU: 26 PID: 1510 Comm: systemd-udevd Not tainted
> 5.15.2.1-13 #1
>  Hardware name: MICROSOFT CORPORATION, BIOS MICROSOFT CORPORATION
>  Call trace:
>   dump_backtrace+0x0/0x1e0
>   show_stack+0x24/0x30
>   dump_stack_lvl+0x8c/0xb8
>   dump_stack+0x18/0x34
>   panic+0x16c/0x384
>   add_taint+0x0/0xc0
>   arm64_serror_panic+0x7c/0x90
>   arm64_is_fatal_ras_serror+0x34/0xa4
>   do_serror+0x50/0x6c
>   el1h_64_error_handler+0x40/0x74
>   el1h_64_error+0x7c/0x80
>   cppc_get_perf_caps+0xec/0x410
>   cppc_cpufreq_cpu_init+0x74/0x400 [cppc_cpufreq]
>   cpufreq_online+0x2dc/0xa30
>   cpufreq_add_dev+0xc0/0xd4
>   subsys_interface_register+0x134/0x14c
>   cpufreq_register_driver+0x1b0/0x354
>   cppc_cpufreq_init+0x1a8/0x1000 [cppc_cpufreq]
>   do_one_initcall+0x50/0x250
>   do_init_module+0x60/0x27c
>   load_module+0x2300/0x2570
>   __do_sys_finit_module+0xa8/0x114
>   __arm64_sys_finit_module+0x2c/0x3c
>   invoke_syscall+0x78/0x100
>   el0_svc_common.constprop.0+0x180/0x1a0
>   do_el0_svc+0x84/0xa0
>   el0_svc+0x2c/0xc0
>   el0t_64_sync_handler+0xa4/0x12c
>   el0t_64_sync+0x1a4/0x1a8
>
> Instead, use access_width to determine the size and use the offset and wi=
dth
> to shift and mask the bits we want to read/write out. Make sure to add a =
check
> for system memory since pcc redefines the access_width to subspace id. If
> access_width is not set, then fallback to using the bit_width.
>
> Signed-off-by: Jarred White <jarredwhite@linux.microsoft.com>
> CC: srivatsabhat@linux.microsoft.com
> CC: stable@vger.kernel.org #5.15+
> ---
> changelog:
> v1-->v2:
> https://lore.kernel.org/linux-acpi/20231216001312.1160-1-jarredwhite@linu=
x.microsoft.com/
>         1. Fixed coding style errors
>         2. Backwards compatibility with ioremapping of address still an
>                 open question. Suggestions are welcomed.
> v2-->v3:
>         1. Created a fallback mechanism to revert to using the bit_width
>         2. Re-labeled macro to GET_BIT_WIDTH
>         3. Collapsed the if/else statements in the cpc_read() and cpc_wri=
te() routines
>
>  drivers/acpi/cppc_acpi.c | 32 +++++++++++++++++++++++++++-----
>  1 file changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index d155a86a8614..57de7edda7a5 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -166,6 +166,13 @@ show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, n=
ominal_freq);
>  show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, reference_perf);
>  show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time);
>
> +/* Check for valid access_width, otherwise, fallback to using the bit_wi=
dth */
> +#define GET_BIT_WIDTH(reg) ((reg)->access_width ? (8 << ((reg)->access_w=
idth - 1)) : (reg)->bit_width)
> +
> +/* Shift and apply the mask for CPC reads/writes */
> +#define MASK_VAL(reg, val) ((val) >> ((reg)->bit_offset &               =
       \
> +                                       GENMASK(((reg)->bit_width), 0)))
> +
>  static ssize_t show_feedback_ctrs(struct kobject *kobj,
>                 struct kobj_attribute *attr, char *buf)
>  {
> @@ -780,6 +787,7 @@ int acpi_cppc_processor_probe(struct acpi_processor *=
pr)
>                         } else if (gas_t->space_id =3D=3D ACPI_ADR_SPACE_=
SYSTEM_MEMORY) {
>                                 if (gas_t->address) {
>                                         void __iomem *addr;
> +                                       size_t access_width;
>
>                                         if (!osc_cpc_flexible_adr_space_c=
onfirmed) {
>                                                 pr_debug("Flexible addres=
s space capability not supported\n");
> @@ -787,7 +795,9 @@ int acpi_cppc_processor_probe(struct acpi_processor *=
pr)
>                                                         goto out_free;
>                                         }
>
> -                                       addr =3D ioremap(gas_t->address, =
gas_t->bit_width/8);
> +                                       /* Check for access_width for the=
 size, otherwise use bit_width */
> +                                       access_width =3D GET_BIT_WIDTH(ga=
s_t) / 8;
> +                                       addr =3D ioremap(gas_t->address, =
access_width);
>                                         if (!addr)
>                                                 goto out_free;
>                                         cpc_ptr->cpc_regs[i-2].sys_mem_va=
ddr =3D addr;
> @@ -983,6 +993,7 @@ int __weak cpc_write_ffh(int cpunum, struct cpc_reg *=
reg, u64 val)
>  static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 =
*val)
>  {
>         void __iomem *vaddr =3D NULL;
> +       int size;
>         int pcc_ss_id =3D per_cpu(cpu_pcc_subspace_idx, cpu);
>         struct cpc_reg *reg =3D &reg_res->cpc_entry.reg;
>
> @@ -994,7 +1005,7 @@ static int cpc_read(int cpu, struct cpc_register_res=
ource *reg_res, u64 *val)
>         *val =3D 0;
>
>         if (reg->space_id =3D=3D ACPI_ADR_SPACE_SYSTEM_IO) {
> -               u32 width =3D 8 << (reg->access_width - 1);
> +               u32 width =3D GET_BIT_WIDTH(reg);
>                 u32 val_u32;
>                 acpi_status status;
>
> @@ -1018,7 +1029,9 @@ static int cpc_read(int cpu, struct cpc_register_re=
source *reg_res, u64 *val)
>                 return acpi_os_read_memory((acpi_physical_address)reg->ad=
dress,
>                                 val, reg->bit_width);
>
> -       switch (reg->bit_width) {
> +       size =3D GET_BIT_WIDTH(reg);
> +
> +       switch (size) {
>         case 8:
>                 *val =3D readb_relaxed(vaddr);
>                 break;
> @@ -1037,18 +1050,22 @@ static int cpc_read(int cpu, struct cpc_register_=
resource *reg_res, u64 *val)
>                 return -EFAULT;
>         }
>
> +       if (reg->space_id =3D=3D ACPI_ADR_SPACE_SYSTEM_MEMORY)
> +               *val =3D MASK_VAL(reg, *val);
> +
>         return 0;
>  }
>
>  static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64=
 val)
>  {
>         int ret_val =3D 0;
> +       int size;
>         void __iomem *vaddr =3D NULL;
>         int pcc_ss_id =3D per_cpu(cpu_pcc_subspace_idx, cpu);
>         struct cpc_reg *reg =3D &reg_res->cpc_entry.reg;
>
>         if (reg->space_id =3D=3D ACPI_ADR_SPACE_SYSTEM_IO) {
> -               u32 width =3D 8 << (reg->access_width - 1);
> +               u32 width =3D GET_BIT_WIDTH(reg);
>                 acpi_status status;
>
>                 status =3D acpi_os_write_port((acpi_io_address)reg->addre=
ss,
> @@ -1070,7 +1087,12 @@ static int cpc_write(int cpu, struct cpc_register_=
resource *reg_res, u64 val)
>                 return acpi_os_write_memory((acpi_physical_address)reg->a=
ddress,
>                                 val, reg->bit_width);
>
> -       switch (reg->bit_width) {
> +       size =3D GET_BIT_WIDTH(reg);
> +
> +       if (reg->space_id =3D=3D ACPI_ADR_SPACE_SYSTEM_MEMORY)
> +               val =3D MASK_VAL(reg, val);
> +
> +       switch (size) {
>         case 8:
>                 writeb_relaxed(val, vaddr);
>                 break;
> --

Applied as 6.9 material with some edits in the subject and changelog
and some adjustments of the new comments (one edited and one dropped).

Thanks!