On Sun, Feb 02, 2025 at 06:43:04PM -0600, Rob Herring (Arm) wrote:
[...]
> +static void __debug_save_brbe(u64 *brbcr_el1)
> +{
> + *brbcr_el1 = 0;
> +
> + /* Check if the BRBE is enabled */
> + if (!(read_sysreg_el1(SYS_BRBCR) & (BRBCR_ELx_E0BRE | BRBCR_ELx_ExBRE)))
> + return;
> +
> + /*
> + * Prohibit branch record generation while we are in guest.
> + * Since access to BRBCR_EL1 is trapped, the guest can't
> + * modify the filtering set by the host.
> + */
> + *brbcr_el1 = read_sysreg_el1(SYS_BRBCR);
> + write_sysreg_el1(0, SYS_BRBCR);
> +}
Should flush branch record and use isb() before exit host kernel?
I see inconsistence between the function above and BRBE's disable
function. Here it clears E0BRE / ExBRE bits for disabling BRBE, but the
BRBE driver sets the PAUSED bit in BRBFCR_EL1 for disabling BRBE.
Thanks,
Leo
