UEFI tests do not update MSR_GS_BASE during bringup, and continue
using the GS_BASE set up by the UEFI implementation for percpu
storage.
Update this MSR during setup_segments64() to allow storing percpu
data at a sane location reserved by the testcase, and ensure that
this happens before any operation that ends up storing to the percpu
space.
Signed-off-by: Varad Gautam <varad.gautam@xxxxxxxx>
---
lib/x86/setup.c | 9 ++++++---
x86/efi/efistart64.S | 7 +++++++
2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/lib/x86/setup.c b/lib/x86/setup.c
index 7dd6677..5d32d3f 100644
--- a/lib/x86/setup.c
+++ b/lib/x86/setup.c
@@ -170,7 +170,8 @@ void setup_multiboot(struct mbi_bootinfo *bi)
#ifdef CONFIG_EFI
/* From x86/efi/efistart64.S */
-extern void setup_segments64(void);
+extern void setup_segments64(u64 gs_base);
+extern u8 stacktop;
static efi_status_t setup_memory_allocator(efi_bootinfo_t *efi_bootinfo)
{
@@ -271,12 +272,14 @@ static void setup_page_table(void)
static void setup_gdt_tss(void)
{
size_t tss_offset;
+ u64 gs_base;
/* 64-bit setup_tss does not use the stacktop argument. */
tss_offset = setup_tss(NULL);
load_gdt_tss(tss_offset);
- setup_segments64();
+ gs_base = (u64)(&stacktop) - (PAGE_SIZE * (pre_boot_apic_id() + 1));
+ setup_segments64(gs_base);
}
efi_status_t setup_efi(efi_bootinfo_t *efi_bootinfo)
@@ -318,8 +321,8 @@ efi_status_t setup_efi(efi_bootinfo_t *efi_bootinfo)
return status;
}
- reset_apic();
setup_gdt_tss();
+ reset_apic();
setup_idt();
load_idt();
mask_pic_interrupts();
diff --git a/x86/efi/efistart64.S b/x86/efi/efistart64.S
index cb08230..1c38355 100644
--- a/x86/efi/efistart64.S
+++ b/x86/efi/efistart64.S
@@ -44,6 +44,13 @@ setup_segments64:
mov %ax, %gs
mov %ax, %ss
+ /* Setup percpu base */
+ MSR_GS_BASE = 0xc0000101
+ mov %rdi, %rax
+ mov $0, %edx
+ mov $MSR_GS_BASE, %ecx
+ wrmsr
+
/*
* Update the code segment by putting it on the stack before the return
* address, then doing a far return: this will use the new code segment
--
2.35.1
