On Thu, Aug 22, 2024 at 04:10:49PM +0100, Joey Gouly wrote:
POR_EL0 is a register that can be modified by userspace directly, so it must be context switched.
Signed-off-by: Joey Gouly joey.gouly@arm.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will@kernel.org Reviewed-by: Catalin Marinas catalin.marinas@arm.com
arch/arm64/include/asm/cpufeature.h | 6 ++++++ arch/arm64/include/asm/processor.h | 1 + arch/arm64/include/asm/sysreg.h | 3 +++ arch/arm64/kernel/process.c | 28 ++++++++++++++++++++++++++++ 4 files changed, 38 insertions(+)
[...]
+static void permission_overlay_switch(struct task_struct *next) +{
- if (!system_supports_poe())
return;- current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0);
- if (current->thread.por_el0 != next->thread.por_el0) {
write_sysreg_s(next->thread.por_el0, SYS_POR_EL0);/* ISB required for kernel uaccess routines when chaning POR_EL0 */
nit: typo "chaning".
But more substantially, is this just to prevent spurious faults in the context of a new thread using a stale value for POR_EL0?
Will