On Tue, 18 Feb 2025 at 15:09, Cyril Bur <cyrilbur@xxxxxxxxxxxxxxx> wrote:
>
> Currently each character of a string is term_putc()ed individually. This
> causes a round trip into opensbi for each char. Very inefficient
> especially since the interface term_putc() does accept a count.
>
> This patch passes a count to term_putc() in the
> SBI_EXT_DBCN_CONSOLE_WRITE path.
>
> Signed-off-by: Cyril Bur <cyrilbur@xxxxxxxxxxxxxxx>
Reviewed-by: Joel Stanley <joel@xxxxxxxxx>
I added Will to cc so he can take a look and apply this for you.
> ---
> riscv/kvm-cpu.c | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/riscv/kvm-cpu.c b/riscv/kvm-cpu.c
> index 0c171da..84d35f7 100644
> --- a/riscv/kvm-cpu.c
> +++ b/riscv/kvm-cpu.c
> @@ -172,21 +172,23 @@ static bool kvm_cpu_riscv_sbi(struct kvm_cpu *vcpu)
> str_start = guest_flat_to_host(vcpu->kvm, addr);
> addr += vcpu->kvm_run->riscv_sbi.args[0] - 1;
> str_end = guest_flat_to_host(vcpu->kvm, addr);
> - if (!str_start || !str_end) {
> + if (!str_start || !str_end || str_start > str_end) {
> vcpu->kvm_run->riscv_sbi.ret[0] =
> SBI_ERR_INVALID_PARAM;
> break;
> }
> + if (vcpu->kvm_run->riscv_sbi.function_id ==
> + SBI_EXT_DBCN_CONSOLE_WRITE) {
> + int length = (str_end - str_start) + 1;
> +
> + length = term_putc(str_start, length, 0);
> + vcpu->kvm_run->riscv_sbi.ret[1] = length;
> + break;
> + }
> + /* This will be SBI_EXT_DBCN_CONSOLE_READ */
> vcpu->kvm_run->riscv_sbi.ret[1] = 0;
> - while (str_start <= str_end) {
> - if (vcpu->kvm_run->riscv_sbi.function_id ==
> - SBI_EXT_DBCN_CONSOLE_WRITE) {
> - term_putc(str_start, 1, 0);
> - } else {
> - if (!term_readable(0))
> - break;
> - *str_start = term_getc(vcpu->kvm, 0);
> - }
> + while (str_start <= str_end && term_readable(0)) {
> + *str_start = term_getc(vcpu->kvm, 0);
> vcpu->kvm_run->riscv_sbi.ret[1]++;
> str_start++;
> }
> --
> 2.34.1
>
