According to TDX Architecture Specification, 9.8 Interrupt Handling
and APIC Virtualization:
1. Guest TDs must use virtualized x2APIC mode. xAPIC mode(using memory
mapped APIC access) is not allowed.
2. Guest TDs attempts to RDMSR or WRMSR the IA32_APIC_BASE MSR cause a
VE to the guest TD. The guest TD cannot disable the APIC.
Bypass xAPIC initialization and enable x2APIC directly. Set software
enable bit in x2APIC initializaion.
Use uid/apicid mapping to get apicid in setup_tss(). Initially I enabled
x2APIC early so apic_id() could be used. But that brings issue for
multiprocessor support as reading APIC_ID in AP triggers #VE and require
gdt/tss/idt to be initialized early, so setup_gdt_tss() early.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxx>
Reviewed-by: Yu Zhang <yu.c.zhang@xxxxxxxxx>
---
lib/x86/apic.c | 4 ++++
lib/x86/setup.c | 10 +++++++---
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/lib/x86/apic.c b/lib/x86/apic.c
index da8f30134b22..84bfe98c58ff 100644
--- a/lib/x86/apic.c
+++ b/lib/x86/apic.c
@@ -147,6 +147,10 @@ int enable_x2apic(void)
asm ("rdmsr" : "=a"(a), "=d"(d) : "c"(MSR_IA32_APICBASE));
a |= 1 << 10;
asm ("wrmsr" : : "a"(a), "d"(d), "c"(MSR_IA32_APICBASE));
+
+ /* software APIC enabled bit is cleared after reset in TD-guest */
+ x2apic_write(APIC_SPIV, 0x1ff);
+
apic_ops = &x2apic_ops;
return 1;
} else {
diff --git a/lib/x86/setup.c b/lib/x86/setup.c
index fbcd188ebb8f..e834fdfd290c 100644
--- a/lib/x86/setup.c
+++ b/lib/x86/setup.c
@@ -108,8 +108,9 @@ unsigned long setup_tss(u8 *stacktop)
{
u32 id;
tss64_t *tss_entry;
+ static u32 cpus = 0;
- id = apic_id();
+ id = is_tdx_guest() ? id_map[cpus++] : apic_id();
/* Runtime address of current TSS */
tss_entry = &tss[id];
@@ -327,12 +328,15 @@ efi_status_t setup_efi(efi_bootinfo_t *efi_bootinfo)
return status;
}
- reset_apic();
+ /* xAPIC mode isn't allowed in TDX */
+ if (!is_tdx_guest())
+ reset_apic();
setup_gdt_tss();
setup_idt();
load_idt();
mask_pic_interrupts();
- enable_apic();
+ if (!is_tdx_guest())
+ enable_apic();
enable_x2apic();
smp_init();
setup_page_table();
--
2.25.1
