Commit 32c9c801 authored Nov 27, 2017 by Jan Kiszka Committed by Thomas Gleixner Jan 14, 2018

x86/apic: Install an empty physflat_init_apic_ldr



As the comment already stated, there is no need for setting up LDR (and
DFR) in physflat mode as it remains unused (see SDM, 10.6.2.1).
flat_init_apic_ldr only served as a placeholder for a nop operation so
far, causing no harm.

That will change when running over the Jailhouse hypervisor. Here we
must not touch LDR in a way that destroys the mapping originally set up
by the Linux root cell. Jailhouse enforces this setting in order to
efficiently validate any IPI requests sent by a cell.

Avoid a needless clash caused by flat_init_apic_ldr by installing a true
nop handler.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: jailhouse-dev@googlegroups.com
Link: https://lkml.kernel.org/r/f9867d294cdae4d45ed89d3a2e6adb524f4f6794.1511770314.git.jan.kiszka@siemens.com

parent c92a9a46

arch/x86/kernel/apic/apic_flat_64.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -218,6 +218,15 @@ static int physflat_acpi_madt_oem_check(char oem_id, char oem_table_id)
		return 0;
		}

		static void physflat_init_apic_ldr(void)
		{
		/*
		* LDR and DFR are not involved in physflat mode, rather:
		* "In physical destination mode, the destination processor is
		* specified by its local APIC ID [...]." (Intel SDM, 10.6.2.1)
		*/
		}

		static void physflat_send_IPI_allbutself(int vector)
		{
		default_send_IPI_mask_allbutself_phys(cpu_online_mask, vector);
		@@ -251,8 +260,7 @@ static struct apic apic_physflat __ro_after_init = {
		.dest_logical = 0,
		.check_apicid_used = NULL,

		/* not needed, but shouldn't hurt: */
		.init_apic_ldr = flat_init_apic_ldr,
		.init_apic_ldr = physflat_init_apic_ldr,

		.ioapic_phys_id_map = NULL,
		.setup_apic_routing = NULL,