On Tue, Oct 17, 2017 at 06:44:28PM +0100, James Morse wrote: > The Software Delegated Exception Interface (SDEI) is an ARM standard > for registering callbacks from the platform firmware into the OS. > This is typically used to implement RAS notifications. > > Such notifications enter the kernel at the registered entry-point > with the register values of the interrupted CPU context. Because this > is not a CPU exception, it cannot reuse the existing entry code. > (crucially we don't implicitly know which exception level we interrupted), > > Add an sdei-entry.S asm file to set us up for calling into C code. If > the event interrupted code that had interrupts masked, we always return > to that location. Otherwise we pretend this was an IRQ, and use SDEI's > complete_and_resume call to return to vbar_el1 + offset. > > This allows the kernel to deliver signals to user space processes. For > KVM this triggers the world switch, a quick spin round vcpu_run, then > back into the guest, unless there are pending signals. > > Add sdei_mask_local_cpu() calls to the smp_send_stop() code, this covers > the panic() code-path, which doesn't invoke cpuhotplug notifiers. > > Because we can interrupt entry-from/exit-to another EL, we can't trust the > value in sp_el0 or x29, even if we interrupted the kernel, in this case > the code in entry.S will save/restore sp_el0 and use the value in > __entry_task. > > When we have VMAP stacks we can interrupt the stack-overflow test, which > stirs x0 into sp, meaning we have to have our own VMAP stack. > > Signed-off-by: James Morse <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]> > +static __kprobes unsigned long _sdei_handler(struct pt_regs *regs, > + struct sdei_registered_event *arg) > +{ > + u32 mode; > + int i, err = 0; > + const int clobbered_registers = 4; > + u64 elr = read_sysreg(elr_el1); > + u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */ > + unsigned long vbar = read_sysreg(vbar_el1); > + > + /* Retrieve the missing registers values */ > + for (i = 0; i < clobbered_registers; i++) { > + /* from within the handler, this call always succeeds */ > + sdei_api_event_context(i, ®s->regs[i]); > + } > + > + /* > + * We didn't take an exception to get here, set PAN. UAO will be cleared > + * by sdei_event_handler()s set_fs(USER_DS) call. > + */ > + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, > + CONFIG_ARM64_PAN)); We have a similar asm in __cpu_suspend_exit(), so there's precedent. As a separate patch (not part of this series), we should move them into a macro, e.g. __uaccess_disable_hw_pan() (enabling as well for consistency). -- Catalin _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
