Re: [PATCH 1/3] lib: sbi: allow platform to override PMP configuration

Bo Gan
2025-11-11T09:20:16Z

Hi Xiang,

On 11/10/25 21:45, Xiang W wrote:
> 在 2025-11-10一的 19:41 -0800，Bo Gan写道：
>> Platform sometimes wants to override the entire PMP configuration phase,
>> not just performing additional work for each individual PMP entry. This
>> allows platforms to insert SoC/core specific PMP entries in a way that
>> works together with the existing ones set by lib/ code, not conflicting.
>> platform can also choose to merge or skip memory regions in a reasonable
>> way in case there's a shortage of PMP entries.
>>
>> In addition, `sbi_hart_oldpmp_configure` is made public and a callback
>> function `skip` is added, so platform code can built on top of it to
>> simplify PMP configuration override.
>>
>> Signed-off-by: Bo Gan <ganboing@gmail.com>
>> ---
>>  include/sbi/sbi_hart.h     |  9 +++++++++
>>  include/sbi/sbi_platform.h | 33 +++++++++++++++++++++++++++++++++
>>  lib/sbi/sbi_hart.c         | 27 +++++++++++++++++++--------
>>  3 files changed, 61 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
>> index e66dd52f..e5a221bd 100644
>> --- a/include/sbi/sbi_hart.h
>> +++ b/include/sbi/sbi_hart.h
>> @@ -133,6 +133,7 @@ struct sbi_hart_features {
>>  };
>>
>>  struct sbi_scratch;
>> +struct sbi_domain_memregion;
>>
>>  int sbi_hart_reinit(struct sbi_scratch *scratch);
>>  int sbi_hart_init(struct sbi_scratch *scratch, bool cold_boot);
>> @@ -148,6 +149,14 @@ unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch);
>>  unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch);
>>  bool sbi_hart_smepmp_is_fw_region(unsigned int pmp_idx);
>>  int sbi_hart_pmp_configure(struct sbi_scratch *scratch);
>> +int sbi_hart_oldpmp_configure(struct sbi_scratch *scratch,
>> +       unsigned int pmp_start,
> It is recommended to change the declaration from pmp_start to pmp_reserved.
> Otherwise, it might give the misleading impression that the last pmp is
> pmp_start + pmp_count - 1.
>
> Regards,
> Xiang W

Thanks for the review. Yes, this pmp_start/pmp_count is indeed misleading.
I'll address it in the next version.

Bo

>> +       unsigned int pmp_count,
>> +       unsigned int pmp_log2gran,
>> +       unsigned long pmp_addr_max,
>> +       bool (*skip)(struct sbi_domain_memregion *reg,
>> +    void *data),
>> +       void *data);
>>  int sbi_hart_map_saddr(unsigned long base, unsigned long size);
>>  int sbi_hart_unmap_saddr(void);
>>  int sbi_hart_priv_version(struct sbi_scratch *scratch);
>> diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h
>> index d75c12de..c6fc137f 100644
>> --- a/include/sbi/sbi_platform.h
>> +++ b/include/sbi/sbi_platform.h
>> @@ -146,6 +146,11 @@ struct sbi_platform_operations {
>>   unsigned long log2len);
>>   /** platform specific pmp disable on current HART */
>>   void (*pmp_disable)(unsigned int n);
>> +
>> + /** platform pmp configure override on current HART */
>> + int (*pmp_configure)(unsigned int pmp_count,
>> +      unsigned int pmp_log2gran,
>> +      unsigned long pmp_addr_max);
>>  };
>>
>>  /** Platform default per-HART stack size for exception/interrupt handling */
>> @@ -666,6 +671,34 @@ static inline void sbi_platform_pmp_disable(const struct sbi_platform *plat,
>>   sbi_platform_ops(plat)->pmp_disable(n);
>>  }
>>
>> +/**
>> + * Check if platform wants to override PMP configuration
>> + *
>> + * @param plat pointer to struct sbi_platform
>> + */
>> +static inline bool sbi_platform_pmp_override(const struct sbi_platform *plat)
>> +{
>> + return plat && sbi_platform_ops(plat)->pmp_configure;
>> +}
>> +
>> +/**
>> + * Platform PMP configuration override
>> + *
>> + * @param plat pointer to struct sbi_platform
>> + * @param pmp_count number of PMP entries
>> + * @param pmp_log2gran PMP granularity
>> + * @param pmp_addr_max largest value pmpaddr(x) can hold
>> + */
>> +static inline int sbi_platform_pmp_configure(const struct sbi_platform *plat,
>> +      unsigned int pmp_count,
>> +      unsigned int pmp_log2gran,
>> +      unsigned long pmp_addr_max)
>> +{
>> + return sbi_platform_ops(plat)->pmp_configure(pmp_count,
>> +      pmp_log2gran,
>> +      pmp_addr_max);
>> +}
>> +
>>  #endif
>>
>>  #endif
>> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
>> index a91703b4..4425f36b 100644
>> --- a/lib/sbi/sbi_hart.c
>> +++ b/lib/sbi/sbi_hart.c
>> @@ -433,18 +433,24 @@ static int sbi_hart_smepmp_configure(struct sbi_scratch *scratch,
>>   return 0;
>>  }
>>
>> -static int sbi_hart_oldpmp_configure(struct sbi_scratch *scratch,
>> -      unsigned int pmp_count,
>> -      unsigned int pmp_log2gran,
>> -      unsigned long pmp_addr_max)
>> +int sbi_hart_oldpmp_configure(struct sbi_scratch *scratch,
>> +       unsigned int pmp_start,
>> +       unsigned int pmp_count,
>> +       unsigned int pmp_log2gran,
>> +       unsigned long pmp_addr_max,
>> +       bool (*skip)(struct sbi_domain_memregion *reg,
>> +    void *data),
>> +       void *data)
>>  {
>>   struct sbi_domain_memregion *reg;
>>   struct sbi_domain *dom = sbi_domain_thishart_ptr();
>> - unsigned int pmp_idx = 0;
>> + unsigned int pmp_idx = pmp_start;
>>   unsigned int pmp_flags;
>>   unsigned long pmp_addr;
>>
>>   sbi_domain_for_each_memregion(dom, reg) {
>> + if (skip && skip(reg, data))
>> + continue;
>>   if (!is_valid_pmp_idx(pmp_count, pmp_idx))
>>   return SBI_EFAIL;
>>
>> @@ -534,6 +540,7 @@ int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
>>   unsigned int pmp_bits, pmp_log2gran;
>>   unsigned int pmp_count = sbi_hart_pmp_count(scratch);
>>   unsigned long pmp_addr_max;
>> + const struct sbi_platform *plat = sbi_platform_ptr(scratch);
>>
>>   if (!pmp_count)
>>   return 0;
>> @@ -542,12 +549,16 @@ int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
>>   pmp_bits = sbi_hart_pmp_addrbits(scratch) - 1;
>>   pmp_addr_max = (1UL << pmp_bits) | ((1UL << pmp_bits) - 1);
>>
>> - if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP))
>> + if (sbi_platform_pmp_override(plat))
>> + rc = sbi_platform_pmp_configure(plat, pmp_count,
>> + pmp_log2gran, pmp_addr_max);
>> + else if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP))
>>   rc = sbi_hart_smepmp_configure(scratch, pmp_count,
>>   pmp_log2gran, pmp_addr_max);
>>   else
>> - rc = sbi_hart_oldpmp_configure(scratch, pmp_count,
>> - pmp_log2gran, pmp_addr_max);
>> + rc = sbi_hart_oldpmp_configure(scratch, 0, pmp_count,
>> + pmp_log2gran, pmp_addr_max,
>> + NULL, NULL);
>>
>>   /*
>>   * As per section 3.7.2 of privileged specification v1.12,
>> --
>> 2.34.1
>>