Messages in this thread Patch in this message | | | From | Konrad Rzeszutek Wilk <> | Subject | [PATCH 4/4] x86/wakeup/sleep: Use pvops functions for changing GDT entries. | Date | Fri, 5 Apr 2013 16:42:24 -0400 |
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From: "konrad@kernel.org" <konrad@kernel.org>
We check the TSS descriptor before we try to dereference it. Also we document what the value '9' actually means using the AMD64 Architecture Programmer's Manual Volume 2, pg 90: "Hex value 9: Available 64-bit TSS" and pg 91: "The available 32-bit TSS (09h), which is redefined as the available 64-bit TSS."
Without this, on Xen, where the GDT is available as R/O (to protect the hypervisor from the guest modifying it), we end up with a pagetable fault.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> --- arch/x86/power/cpu.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 571176f..6d6e907 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -133,7 +133,10 @@ static void fix_processor_context(void) { int cpu = smp_processor_id(); struct tss_struct *t = &per_cpu(init_tss, cpu); - +#ifdef CONFIG_X86_64 + struct desc_struct *desc = get_cpu_gdt_table(cpu); + tss_desc tss; +#endif set_tss_desc(cpu, t); /* * This just modifies memory; should not be * necessary. But... This is necessary, because @@ -142,7 +145,9 @@ static void fix_processor_context(void) */ #ifdef CONFIG_X86_64 - get_cpu_gdt_table(cpu)[GDT_ENTRY_TSS].type = 9; + memcpy(&tss, &desc[GDT_ENTRY_TSS], sizeof(tss_desc)); + tss.type = 0x9; /* The available 64-bit TSS (see AMD vol 2, pg 91 */ + write_gdt_entry(desc, GDT_ENTRY_TSS, &tss, DESC_TSS); syscall_init(); /* This sets MSR_*STAR and related */ #endif -- 1.8.1.4
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