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| author | Andy Lutomirski <luto@kernel.org> | 2017-03-22 22:32:34 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-03-23 08:25:08 +0100 |
| commit | b23adb7d3f7d1d7cce03db9704de67a99ceeda38 (patch) | |
| tree | 942b72751d6b244a0f5f9a6764261cf2cb26672f /arch/x86/kernel/cpu/common.c | |
| parent | x86/gdt: Get rid of the get_*_gdt_*_vaddr() helpers (diff) | |
| download | linux-b23adb7d3f7d1d7cce03db9704de67a99ceeda38.tar.xz linux-b23adb7d3f7d1d7cce03db9704de67a99ceeda38.zip | |
x86/xen/gdt: Use X86_FEATURE_XENPV instead of globals for the GDT fixup
Xen imposes special requirements on the GDT. Rather than using a
global variable for the pgprot, just use an explicit special case
for Xen -- this makes it clearer what's going on. It also debloats
64-bit kernels very slightly.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/e9ea96abbfd6a8c87753849171bb5987ecfeb523.1490218061.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 28 |
1 files changed, 17 insertions, 11 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index f6e20e2dbfa5..8ee32119144d 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -448,21 +448,27 @@ void load_percpu_segment(int cpu) load_stack_canary_segment(); } -/* - * On 64-bit the GDT remapping is read-only. - * A global is used for Xen to change the default when required. - */ +/* Setup the fixmap mapping only once per-processor */ +static inline void setup_fixmap_gdt(int cpu) +{ #ifdef CONFIG_X86_64 -pgprot_t pg_fixmap_gdt_flags = PAGE_KERNEL_RO; + /* On 64-bit systems, we use a read-only fixmap GDT. */ + pgprot_t prot = PAGE_KERNEL_RO; #else -pgprot_t pg_fixmap_gdt_flags = PAGE_KERNEL; + /* + * On native 32-bit systems, the GDT cannot be read-only because + * our double fault handler uses a task gate, and entering through + * a task gate needs to change an available TSS to busy. If the GDT + * is read-only, that will triple fault. + * + * On Xen PV, the GDT must be read-only because the hypervisor requires + * it. + */ + pgprot_t prot = boot_cpu_has(X86_FEATURE_XENPV) ? + PAGE_KERNEL_RO : PAGE_KERNEL; #endif -/* Setup the fixmap mapping only once per-processor */ -static inline void setup_fixmap_gdt(int cpu) -{ - __set_fixmap(get_cpu_gdt_ro_index(cpu), get_cpu_gdt_paddr(cpu), - pg_fixmap_gdt_flags); + __set_fixmap(get_cpu_gdt_ro_index(cpu), get_cpu_gdt_paddr(cpu), prot); } /* Load the original GDT from the per-cpu structure */ |