* Use MOV CR instead of LMSW. LMSW has no decode assist at all on AMD CPUs,
forcing us to fully emulate the instruction.
* Use __attribute__((used)) to fix the comment about ap_start().
* Have ap_start() perform a self-INIT for APs, rather than having boot_cpu()
do it. This is marginally more parallel, and reduces the amount of remote
vCPU management that Xen has to do on behalf of the guest.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Roger Pau Monné <roger....@citrix.com>
CC: Wei Liu <w...@xen.org>
---
tools/firmware/hvmloader/smp.c | 46 ++++++++++++++++++++++++++++--------------
1 file changed, 31 insertions(+), 15 deletions(-)
diff --git a/tools/firmware/hvmloader/smp.c b/tools/firmware/hvmloader/smp.c
index 082b17f13818..80154950ac32 100644
--- a/tools/firmware/hvmloader/smp.c
+++ b/tools/firmware/hvmloader/smp.c
@@ -35,9 +35,9 @@ asm (
" mov %cs,%ax \n"
" mov %ax,%ds \n"
" lgdt gdt_desr-ap_boot_start\n"
- " xor %ax, %ax \n"
- " inc %ax \n"
- " lmsw %ax \n"
+ " mov %cr0, %eax \n"
+ " or $1, %al \n"
+ " mov %eax, %cr0 \n"
" ljmpl $0x08,$1f \n"
"gdt_desr: \n"
" .word gdt_end - gdt - 1 \n"
@@ -50,8 +50,6 @@ asm (
" movl $stack_top,%esp \n"
" movl %esp,%ebp \n"
" call ap_start \n"
- "1: hlt \n"
- " jmp 1b \n"
" \n"
" .align 8 \n"
"gdt: \n"
@@ -68,14 +66,37 @@ asm (
" .text \n"
);
-void ap_start(void); /* non-static avoids unused-function compiler warning */
-/*static*/ void ap_start(void)
+static void __attribute__((used)) ap_start(void)
{
- printf(" - CPU%d ... ", ap_cpuid);
+ unsigned int cpu = ap_cpuid;
+
+ printf(" - CPU%d ... ", cpu);
cacheattr_init();
printf("done.\n");
- wmb();
- ap_callin = 1;
+
+ /*
+ * Call in to the BSP. For APs, take ourselves offline.
+ *
+ * We must not use the stack after calling in to the BSP.
+ */
+ asm volatile (
+ " movb $1, ap_callin \n"
+
+ " test %[icr2], %[icr2] \n"
+ " jz .Lbsp \n"
+
+ " movl %[icr2], %[ICR2] \n"
+ " movl %[init], %[ICR1] \n"
+ "1: hlt \n"
+ " jmp 1b \n"
+
+ ".Lbsp: \n"
+ :
+ : [icr2] "r" (SET_APIC_DEST_FIELD(LAPIC_ID(cpu))),
+ [init] "i" (APIC_DM_INIT),
+ [ICR1] "m" (*(uint32_t *)(LAPIC_BASE_ADDRESS + APIC_ICR)),
+ [ICR2] "m" (*(uint32_t *)(LAPIC_BASE_ADDRESS + APIC_ICR2))
+ : "memory" );
}
static void lapic_wait_ready(void)
@@ -111,11 +132,6 @@ static void boot_cpu(unsigned int cpu)
*/
while ( !ap_callin )
cpu_relax();
-
- /* Take the secondary processor offline. */
- lapic_write(APIC_ICR2, icr2);
- lapic_write(APIC_ICR, APIC_DM_INIT);
- lapic_wait_ready();
}
void smp_initialise(void)
--
2.11.0
