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authorAndy Lutomirski <luto@kernel.org>2017-02-22 07:36:16 -0800
committerRadim Krčmář <rkrcmar@redhat.com>2017-03-01 17:03:22 +0100
commitb7ceaec112aa35aa287325754d8c52b8304892cd (patch)
treeaf5014f643adf8db9d82178bfb22f68062ed41c2
parente3736c3eb3a6f7c0966923b629c9f92b558aa9c7 (diff)
downloadop-kernel-dev-b7ceaec112aa35aa287325754d8c52b8304892cd.zip
op-kernel-dev-b7ceaec112aa35aa287325754d8c52b8304892cd.tar.gz
x86/asm: Tidy up TSS limit code
In an earlier version of the patch ("x86/kvm/vmx: Defer TR reload after VM exit") that introduced TSS limit validity tracking, I confused which helper was which. On reflection, the names I chose sucked. Rename the helpers to make it more obvious what's going on and add some comments. While I'm at it, clear __tss_limit_invalid when force-reloading as well as when contitionally reloading, since any TR reload fixes the limit. Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
-rw-r--r--arch/x86/include/asm/desc.h18
-rw-r--r--arch/x86/kernel/ioport.c8
-rw-r--r--arch/x86/kernel/process.c6
3 files changed, 21 insertions, 11 deletions
diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index cb8f914..1548ca9 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -205,6 +205,8 @@ static inline void native_load_tr_desc(void)
asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
}
+DECLARE_PER_CPU(bool, __tss_limit_invalid);
+
static inline void force_reload_TR(void)
{
struct desc_struct *d = get_cpu_gdt_table(smp_processor_id());
@@ -220,18 +222,20 @@ static inline void force_reload_TR(void)
write_gdt_entry(d, GDT_ENTRY_TSS, &tss, DESC_TSS);
load_TR_desc();
+ this_cpu_write(__tss_limit_invalid, false);
}
-DECLARE_PER_CPU(bool, need_tr_refresh);
-
-static inline void refresh_TR(void)
+/*
+ * Call this if you need the TSS limit to be correct, which should be the case
+ * if and only if you have TIF_IO_BITMAP set or you're switching to a task
+ * with TIF_IO_BITMAP set.
+ */
+static inline void refresh_tss_limit(void)
{
DEBUG_LOCKS_WARN_ON(preemptible());
- if (unlikely(this_cpu_read(need_tr_refresh))) {
+ if (unlikely(this_cpu_read(__tss_limit_invalid)))
force_reload_TR();
- this_cpu_write(need_tr_refresh, false);
- }
}
/*
@@ -250,7 +254,7 @@ static inline void invalidate_tss_limit(void)
if (unlikely(test_thread_flag(TIF_IO_BITMAP)))
force_reload_TR();
else
- this_cpu_write(need_tr_refresh, true);
+ this_cpu_write(__tss_limit_invalid, true);
}
static inline void native_load_gdt(const struct desc_ptr *dtr)
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index b01bc8517..875d3d2 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -47,8 +47,14 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
t->io_bitmap_ptr = bitmap;
set_thread_flag(TIF_IO_BITMAP);
+ /*
+ * Now that we have an IO bitmap, we need our TSS limit to be
+ * correct. It's fine if we are preempted after doing this:
+ * with TIF_IO_BITMAP set, context switches will keep our TSS
+ * limit correct.
+ */
preempt_disable();
- refresh_TR();
+ refresh_tss_limit();
preempt_enable();
}
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 7780efa..0b30259 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -65,8 +65,8 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
};
EXPORT_PER_CPU_SYMBOL(cpu_tss);
-DEFINE_PER_CPU(bool, need_tr_refresh);
-EXPORT_PER_CPU_SYMBOL_GPL(need_tr_refresh);
+DEFINE_PER_CPU(bool, __tss_limit_invalid);
+EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid);
/*
* this gets called so that we can store lazy state into memory and copy the
@@ -218,7 +218,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
* Make sure that the TSS limit is correct for the CPU
* to notice the IO bitmap.
*/
- refresh_TR();
+ refresh_tss_limit();
} else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
/*
* Clear any possible leftover bits:
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