How to enable hardware translation when progbufsize too small

[lz-bro]

Hardware translation requires a program buffer size of at least 4. Can we use a register_write_direct function instead of two instructions csrrsi zero, dcsr, dcsr_mprven and csrrci zero, dcsr, dcsr_mprven ?

riscv-openocd/src/target/riscv/riscv-013.c

Lines 2008 to 2013 in f82c5a7

	if (info->progbufsize < 4 && riscv_virt2phys_mode_is_hw(target)) {
	LOG_TARGET_ERROR(target, "software address translation "
	"is not available on this target. It requires a "
	"program buffer size of at least 4. (progbufsize=%d) "
	"Use `riscv set_enable_virtual off` to continue.", info->progbufsize);
	}

riscv-openocd/src/target/riscv/riscv-013.c

Lines 3120 to 3126 in f82c5a7

	* modify_privilege function used only for program buffer memory access.
	* Privilege modification requires progbuf size to be at least 5 */
	if (!has_sufficient_progbuf(target, 5)) {
	LOG_TARGET_WARNING(target, "Can't modify privilege to provide "
	"hardware translation: program buffer too small.");
	return ERROR_OK;
	}

riscv-openocd/src/target/riscv/riscv-013.c

Lines 4191 to 4206 in f82c5a7

	static int riscv_program_load_mprv(struct riscv_program *p, enum gdb_regno d,
	enum gdb_regno b, int offset, unsigned int size, bool mprven)
	{
	if (mprven && riscv_program_csrrsi(p, GDB_REGNO_ZERO, CSR_DCSR_MPRVEN,
	GDB_REGNO_DCSR) != ERROR_OK)
	return ERROR_FAIL;
	if (riscv_program_load(p, d, b, offset, size) != ERROR_OK)
	return ERROR_FAIL;
	if (mprven && riscv_program_csrrci(p, GDB_REGNO_ZERO, CSR_DCSR_MPRVEN,
	GDB_REGNO_DCSR) != ERROR_OK)
	return ERROR_FAIL;
	return ERROR_OK;
	}

[en-sc]

@lz-bro, AFAIK dcsr modification can be moved out of program buffer and into modify_privilege().
However, I'd like to ask you to avoid using register_read/write_direct() functions. I believe it's safer to use the standard riscv_reg_get/riscv_reg_set functions -- there is no need to bypass the register cache.

[lz-bro]

@lz-bro, AFAIK dcsr modification can be moved out of program buffer and into modify_privilege(). However, I'd like to ask you to avoid using register_read/write_direct() functions. I believe it's safer to use the standard riscv_reg_get/riscv_reg_set functions -- there is no need to bypass the register cache.

I found that the register_read/write_direct() was used by modify_privilege(), and even the riscv-013. c