Re: [PATCH v4 0/3] Add eager FP and RISC-V vector context switching support

On 5/13/26 08:42, Anup Patel wrote:
> On Wed, May 13, 2026 at 12:44 PM <[email protected]> wrote:
>>
>> Hi Anup,
>>         Thank you for taking out time and reviewing the patches.
>> Following your review comments, I have made following changes. Also I have
>> tested the changes.
>>
>> The changes include:
>>         - Dropping CONFIG_SBI_MAX_VLENB and sbi_vector_domain_init()
>>         - struct sbi_vector_context vec_ctx is now struct * in
>>           'struct hart_context'
>>         - changing READ_CSR and WRITE_CSR to vcsr_read and vcsr_write
> 
> I think you misunderstood my previous comment. We already
> have csr_read() and csr_write() defined in riscv_asm.h so use
> these macros instead of introducing  vcsr_read() and vcsr_write().
> 
>>
>> I have covered all your comments, please can you have a look and let me know.
>>
> 
> Regards,
> Anup

Hi Anup,
        Thanks,

There is subtle difference between csr_read/write and vcsr_read/write in
the context that this explicitly enables and isolates the RISC-V Vector
(V) extension during compilation. This allows the program to read
vector-specific Control and Status Registers (such as vlenb, vl, or
vtype) without requiring the entire project to be compiled with global
vector support.

Vector Architecture Override: The directive .option arch, +v dynamically
tells the assembler that the Vector extension is supported for this
specific instruction block. A standard csr_read lacks this, causing
compilation to fail if vector registers are accessed without global
-march vector flags.
Context Protection: The .option push and .option pop directives
safeguard the build environment. They save the original compiler
options, temporarily inject the vector extension, and immediately
restore the original settings so subsequent code is unaffected.
Memory Serialization: The inclusion of the "memory" clobber acts as a
optimization barrier. It prevents the compiler from reordering memory
reads or writes around the CSR operation, which is critical for vector
state updates.

So should I update it to normal csr_read/write instead?

Thanks
Dave

-- 
opensbi mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/opensbi