Re: [PATCH v7 67/72] x86/smpboot: Load TSS and getcpu GDT entry before loading IDT
On Tue, Sep 08, 2020 at 07:20:42PM +0200, Borislav Petkov wrote:
> On Mon, Sep 07, 2020 at 03:16:08PM +0200, Joerg Roedel wrote:
> > +void cpu_init_exception_handling(void)
> > +{
> > + struct tss_struct *tss = this_cpu_ptr(_tss_rw);
> > + int cpu = raw_smp_processor_id();
> > +
> > + /* paranoid_entry() gets the CPU number from the GDT */
> > + setup_getcpu(cpu);
> > +
> > + /* IST vectors need TSS to be set up. */
> > + tss_setup_ist(tss);
> > + tss_setup_io_bitmap(tss);
> > + set_tss_desc(cpu, _cpu_entry_area(cpu)->tss.x86_tss);
> > +
> > + load_TR_desc();
>
> Aha, this is what you mean here in your 0th message. I'm guessing it is
> ok to do those things twice in start_secondary...
Yes, I think its best to do it twice, so that cpu_init() stays the CPU
state barrier it should be, independent of what happens before.
Joerg
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Re: [PATCH v7 67/72] x86/smpboot: Load TSS and getcpu GDT entry before loading IDT
On Mon, Sep 07, 2020 at 03:16:08PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel
>
> The IDT on 64bit contains vectors which use paranoid_entry() and/or IST
> stacks. To make these vectors work the TSS and the getcpu GDT entry need
> to be set up before the IDT is loaded.
>
> Signed-off-by: Joerg Roedel
> ---
> arch/x86/include/asm/processor.h | 1 +
> arch/x86/kernel/cpu/common.c | 23 +++
> arch/x86/kernel/smpboot.c| 2 +-
> 3 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/processor.h
> b/arch/x86/include/asm/processor.h
> index d8a82e650810..5ac507586769 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -696,6 +696,7 @@ extern void load_direct_gdt(int);
> extern void load_fixmap_gdt(int);
> extern void load_percpu_segment(int);
> extern void cpu_init(void);
> +extern void cpu_init_exception_handling(void);
> extern void cr4_init(void);
>
> static inline unsigned long get_debugctlmsr(void)
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 1d65365363a1..a9527c0c38fb 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1854,6 +1854,29 @@ static inline void tss_setup_io_bitmap(struct
> tss_struct *tss)
> #endif
> }
>
> +/*
> + * Setup everything needed to handle exceptions from the IDT, including the
> IST
> + * exceptions which use paranoid_entry()
> + */
> +void cpu_init_exception_handling(void)
> +{
> + struct tss_struct *tss = this_cpu_ptr(_tss_rw);
> + int cpu = raw_smp_processor_id();
> +
> + /* paranoid_entry() gets the CPU number from the GDT */
> + setup_getcpu(cpu);
> +
> + /* IST vectors need TSS to be set up. */
> + tss_setup_ist(tss);
> + tss_setup_io_bitmap(tss);
> + set_tss_desc(cpu, _cpu_entry_area(cpu)->tss.x86_tss);
> +
> + load_TR_desc();
Aha, this is what you mean here in your 0th message. I'm guessing it is
ok to do those things twice in start_secondary...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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[PATCH v7 67/72] x86/smpboot: Load TSS and getcpu GDT entry before loading IDT
From: Joerg Roedel
The IDT on 64bit contains vectors which use paranoid_entry() and/or IST
stacks. To make these vectors work the TSS and the getcpu GDT entry need
to be set up before the IDT is loaded.
Signed-off-by: Joerg Roedel
---
arch/x86/include/asm/processor.h | 1 +
arch/x86/kernel/cpu/common.c | 23 +++
arch/x86/kernel/smpboot.c| 2 +-
3 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index d8a82e650810..5ac507586769 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -696,6 +696,7 @@ extern void load_direct_gdt(int);
extern void load_fixmap_gdt(int);
extern void load_percpu_segment(int);
extern void cpu_init(void);
+extern void cpu_init_exception_handling(void);
extern void cr4_init(void);
static inline unsigned long get_debugctlmsr(void)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 1d65365363a1..a9527c0c38fb 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1854,6 +1854,29 @@ static inline void tss_setup_io_bitmap(struct tss_struct
*tss)
#endif
}
+/*
+ * Setup everything needed to handle exceptions from the IDT, including the IST
+ * exceptions which use paranoid_entry()
+ */
+void cpu_init_exception_handling(void)
+{
+ struct tss_struct *tss = this_cpu_ptr(_tss_rw);
+ int cpu = raw_smp_processor_id();
+
+ /* paranoid_entry() gets the CPU number from the GDT */
+ setup_getcpu(cpu);
+
+ /* IST vectors need TSS to be set up. */
+ tss_setup_ist(tss);
+ tss_setup_io_bitmap(tss);
+ set_tss_desc(cpu, _cpu_entry_area(cpu)->tss.x86_tss);
+
+ load_TR_desc();
+
+ /* Finally load the IDT */
+ load_current_idt();
+}
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index f5ef689dd62a..de776b2e6046 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -227,7 +227,7 @@ static void notrace start_secondary(void *unused)
load_cr3(swapper_pg_dir);
__flush_tlb_all();
#endif
- load_current_idt();
+ cpu_init_exception_handling();
cpu_init();
x86_cpuinit.early_percpu_clock_init();
preempt_disable();
--
2.28.0
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