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[Xen-devel] [PATCH 14/15] paravirtualize IO permission bitmap

To: "H. Peter Anvin" <hpa@xxxxxxxxx>
Subject: [Xen-devel] [PATCH 14/15] paravirtualize IO permission bitmap
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Mon, 23 Mar 2009 11:09:58 -0700
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Christophe Saout <chtephan@xxxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>
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From: Christophe Saout <chtephan@xxxxxxxxxxxxxxxxxxxx>

Impact: make ioperm bitmap work under Xen

A PV Xen guest kernel has no TSS of its own, so the IO permission
bitmap must be paravirtualized.  This patch adds set_io_bitmap
as a paravirt op, and defines a native version which updates the tss,
and a Xen version which uses a hypercall.

This is much easier now that 32 and 64-bit use the same code to
manage the IO bitmap.

Signed-off-by: Christophe Saout <chtephan@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/include/asm/paravirt.h  |    9 +++++++++
 arch/x86/include/asm/processor.h |    4 ++++
 arch/x86/kernel/ioport.c         |   34 ++++++++++++++++++++++++++--------
 arch/x86/kernel/paravirt.c       |    1 +
 arch/x86/kernel/process.c        |   27 +++++++--------------------
 arch/x86/xen/enlighten.c         |   16 ++++++++++++++++
 6 files changed, 63 insertions(+), 28 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index bc384be..fd2c31b 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -156,6 +156,8 @@ struct pv_cpu_ops {
        void (*load_sp0)(struct tss_struct *tss, struct thread_struct *t);
 
        void (*set_iopl_mask)(unsigned mask);
+       void (*set_io_bitmap)(struct thread_struct *thread,
+                             int changed, unsigned long bytes_updated);
 
        void (*wbinvd)(void);
        void (*io_delay)(void);
@@ -996,11 +998,18 @@ static inline void write_idt_entry(gate_desc *dt, int 
entry, const gate_desc *g)
 {
        PVOP_VCALL3(pv_cpu_ops.write_idt_entry, dt, entry, g);
 }
+
 static inline void set_iopl_mask(unsigned mask)
 {
        PVOP_VCALL1(pv_cpu_ops.set_iopl_mask, mask);
 }
 
+static inline void set_io_bitmap(struct thread_struct *thread,
+                                 int changed, unsigned long bytes_updated)
+{
+       PVOP_VCALL3(pv_cpu_ops.set_io_bitmap, thread, changed, bytes_updated);
+}
+
 /* The paravirtualized I/O functions */
 static inline void slow_down_io(void)
 {
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 34c5237..0ed4cba 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -538,6 +538,9 @@ static inline void native_set_iopl_mask(unsigned mask)
 #endif
 }
 
+extern void native_set_io_bitmap(struct thread_struct *thread,
+                                 int changed, unsigned long updated_bytes);
+
 static inline void
 native_load_sp0(struct tss_struct *tss, struct thread_struct *thread)
 {
@@ -579,6 +582,7 @@ static inline void load_sp0(struct tss_struct *tss,
 }
 
 #define set_iopl_mask native_set_iopl_mask
+#define set_io_bitmap native_set_io_bitmap
 #endif /* CONFIG_PARAVIRT */
 
 /*
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 99c4d30..5a12c9f 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -30,14 +30,31 @@ static void set_bitmap(unsigned long *bitmap, unsigned int 
base,
        }
 }
 
+void native_set_io_bitmap(struct thread_struct *t,
+                          int changed, unsigned long bytes_updated)
+{
+       struct tss_struct *tss;
+
+       if (!bytes_updated)
+               return;
+
+       tss = &__get_cpu_var(init_tss);
+
+       /* Update the TSS: */
+       if (t->io_bitmap_ptr)
+               memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+       else
+               memset(tss->io_bitmap, 0xff, bytes_updated);
+}
+
 /*
  * this changes the io permissions bitmap in the current task.
  */
 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
 {
        struct thread_struct *t = &current->thread;
-       struct tss_struct *tss;
        unsigned int i, max_long, bytes, bytes_updated;
+       int changed;
 
        if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
                return -EINVAL;
@@ -58,16 +75,18 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned 
long num, int turn_on)
                memset(bitmap, 0xff, IO_BITMAP_BYTES);
                t->io_bitmap_ptr = bitmap;
                set_thread_flag(TIF_IO_BITMAP);
-       }
+               changed = 1;
+       } else
+               changed = 0;
 
        /*
-        * do it in the per-thread copy and in the TSS ...
+        * do it in the per-thread copy
         *
-        * Disable preemption via get_cpu() - we must not switch away
+        * Disable preemption - we must not switch away
         * because the ->io_bitmap_max value must match the bitmap
         * contents:
         */
-       tss = &per_cpu(init_tss, get_cpu());
+       preempt_disable();
 
        set_bitmap(t->io_bitmap_ptr, from, num, !turn_on);
 
@@ -85,10 +104,9 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned 
long num, int turn_on)
 
        t->io_bitmap_max = bytes;
 
-       /* Update the TSS: */
-       memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+       set_io_bitmap(t, changed, bytes_updated);
 
-       put_cpu();
+       preempt_enable();
 
        return 0;
 }
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index aa34423..1c15178 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -398,6 +398,7 @@ struct pv_cpu_ops pv_cpu_ops = {
        .swapgs = native_swapgs,
 
        .set_iopl_mask = native_set_iopl_mask,
+       .set_io_bitmap = native_set_io_bitmap,
        .io_delay = native_io_delay,
 
        .start_context_switch = paravirt_nop,
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ac25491..174ab04 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -71,16 +71,12 @@ void exit_thread(void)
        unsigned long *bp = t->io_bitmap_ptr;
 
        if (bp) {
-               struct tss_struct *tss = &per_cpu(init_tss, get_cpu());
-
+               preempt_disable();
                t->io_bitmap_ptr = NULL;
                clear_thread_flag(TIF_IO_BITMAP);
-               /*
-                * Careful, clear this in the TSS too:
-                */
-               memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
+               set_io_bitmap(t, 1, t->io_bitmap_max);
                t->io_bitmap_max = 0;
-               put_cpu();
+               preempt_enable();
                kfree(bp);
        }
 
@@ -211,19 +207,10 @@ void __switch_to_xtra(struct task_struct *prev_p, struct 
task_struct *next_p,
                        hard_enable_TSC();
        }
 
-       if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
-               /*
-                * Copy the relevant range of the IO bitmap.
-                * Normally this is 128 bytes or less:
-                */
-               memcpy(tss->io_bitmap, next->io_bitmap_ptr,
-                      max(prev->io_bitmap_max, next->io_bitmap_max));
-       } else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
-               /*
-                * Clear any possible leftover bits:
-                */
-               memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
-       }
+       if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP) ||
+           test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))
+               set_io_bitmap(next, 1,
+                             max(prev->io_bitmap_max, next->io_bitmap_max));
 }
 
 int sys_fork(struct pt_regs *regs)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 213e1ba..61ce3ae 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -568,6 +568,21 @@ static void xen_set_iopl_mask(unsigned mask)
        HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
 }
 
+static void xen_set_io_bitmap(struct thread_struct *thread,
+                              int changed, unsigned long bytes_updated)
+{
+       struct physdev_set_iobitmap set_iobitmap;
+
+       if (!changed)
+               return;
+
+       set_xen_guest_handle(set_iobitmap.bitmap,
+                            (char *)thread->io_bitmap_ptr);
+       set_iobitmap.nr_ports = thread->io_bitmap_ptr ? IO_BITMAP_BITS : 0;
+       WARN_ON(HYPERVISOR_physdev_op(PHYSDEVOP_set_iobitmap,
+                                     &set_iobitmap));
+}
+
 static void xen_io_delay(void)
 {
 }
@@ -861,6 +876,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = {
        .load_sp0 = xen_load_sp0,
 
        .set_iopl_mask = xen_set_iopl_mask,
+       .set_io_bitmap = xen_set_io_bitmap,
        .io_delay = xen_io_delay,
 
        /* Xen takes care of %gs when switching to usermode for us */
-- 
1.6.0.6


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