Messages in this thread | | | Date | Wed, 22 Feb 2023 22:49:26 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 4/6] x86/smpbppt: Remove early_gdt_descr on 64-bit |
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On February 22, 2023 2:12:59 PM PST, Brian Gerst <brgerst@gmail.com> wrote: >Build the GDT descriptor on the stack instead. > >Signed-off-by: Brian Gerst <brgerst@gmail.com> >--- > arch/x86/kernel/acpi/sleep.c | 2 -- > arch/x86/kernel/head_64.S | 19 +++++++------------ > 2 files changed, 7 insertions(+), 14 deletions(-) > >diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c >index 008fda8b1982..6538ddb55f28 100644 >--- a/arch/x86/kernel/acpi/sleep.c >+++ b/arch/x86/kernel/acpi/sleep.c >@@ -114,8 +114,6 @@ int x86_acpi_suspend_lowlevel(void) > #else /* CONFIG_64BIT */ > #ifdef CONFIG_SMP > current->thread.sp = (unsigned long)temp_stack + sizeof(temp_stack); >- early_gdt_descr.address = >- (unsigned long)get_cpu_gdt_rw(smp_processor_id()); > initial_gs = per_cpu_offset(smp_processor_id()); > /* Force the startup into boot mode */ > saved_smpboot_ctrl = xchg(&smpboot_control, 0); >diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S >index f7905ba4b992..0dd57d573a0e 100644 >--- a/arch/x86/kernel/head_64.S >+++ b/arch/x86/kernel/head_64.S >@@ -245,7 +245,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) > #ifdef CONFIG_SMP > /* > * Is this the boot CPU coming up? If so everything is available >- * in initial_gs and early_gdt_descr. >+ * in initial_gs. > */ > movl smpboot_control(%rip), %edx > testl $STARTUP_SECONDARY, %edx >@@ -313,11 +313,6 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) > /* Save it for GS BASE setup */ > movq %rbx, initial_gs(%rip) > >- /* Calculate the GDT address */ >- movq $gdt_page, %rcx >- addq %rbx, %rcx >- movq %rcx, early_gdt_descr_base(%rip) >- > movq %rbx, %rdx > #else > xorl %edx, %edx >@@ -339,7 +334,12 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) > * addresses where we're currently running on. We have to do that here > * because in 32bit we couldn't load a 64bit linear address. > */ >- lgdt early_gdt_descr(%rip) >+ subq $16, %rsp >+ movw $(GDT_SIZE-1), (%rsp) >+ leaq gdt_page(%rdx), %rax >+ movq %rax, 2(%rsp) >+ lgdt (%rsp) >+ addq $16, %rsp > > /* set up data segments */ > xorl %eax,%eax >@@ -754,11 +754,6 @@ SYM_DATA_END(level1_fixmap_pgt) > > .data > .align 16 >- >-SYM_DATA(early_gdt_descr, .word GDT_ENTRIES*8-1) >-SYM_DATA_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page)) >- >- .align 16 > SYM_DATA(smpboot_control, .long 0) > > .align 16
This is known to break at least some hypervisors, probably old by now, but...
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