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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH RFC v13 12/20] pvh: read_descriptor for PVH guests.
This is in preparation for enabling emulated privops for PVH guests.
This one unfortunately has a bit more of an impedance mismatch:
* For PV, the selector is hard-coded in by passing #name in the
#define. For PVH, we have to do a switch statement.
* For PV, given the desrciptor, it can read the resulting base, limit,
&c directly; for PVH, we have to read the values currently loaded in the vmcs.
This leads to a rather awkward construct where we *both* read the
descriptor, *and* specify a selector, and introduce an intermediate function,
read_descriptor_sel.
Unfortunately, without introducing a rather pointless switch()
statement to the PV path similar to the one in the PVH path, there's
no way to make this less awkward.
Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v13: Removed stray space
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
---
xen/arch/x86/traps.c | 73 ++++++++++++++++++++++++++++++++++++++------
xen/include/asm-x86/desc.h | 4 ++-
2 files changed, 66 insertions(+), 11 deletions(-)
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 1eac9ff..0463697 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1518,6 +1518,49 @@ static int read_descriptor(unsigned int sel,
return 1;
}
+static int read_descriptor_sel(unsigned int sel,
+ enum x86_segment which_sel,
+ struct vcpu *v,
+ const struct cpu_user_regs *regs,
+ unsigned long *base,
+ unsigned long *limit,
+ unsigned int *ar,
+ unsigned int vm86attr)
+{
+ struct segment_register seg;
+ bool_t long_mode;
+
+ if ( !is_pvh_vcpu(v) )
+ return read_descriptor(sel, v, regs, base, limit, ar, vm86attr);
+
+ hvm_get_segment_register(v, x86_seg_cs, &seg);
+ long_mode = seg.attr.fields.l;
+
+ if ( which_sel != x86_seg_cs )
+ hvm_get_segment_register(v, which_sel, &seg);
+
+ /* "ar" is returned packed as in segment_attributes_t. Fix it up. */
+ *ar = seg.attr.bytes;
+ *ar = (*ar & 0xff) | ((*ar & 0xf00) << 4);
+ *ar <<= 8;
+
+ if ( long_mode )
+ {
+ *limit = ~0UL;
+
+ if ( which_sel < x86_seg_fs )
+ {
+ *base = 0UL;
+ return 1;
+ }
+ }
+ else
+ *limit = seg.limit;
+
+ *base = seg.base;
+ return 1;
+}
+
static int read_gate_descriptor(unsigned int gate_sel,
const struct vcpu *v,
unsigned int *sel,
@@ -1845,6 +1888,7 @@ static int is_cpufreq_controller(struct domain *d)
static int emulate_privileged_op(struct cpu_user_regs *regs)
{
+ enum x86_segment which_sel;
struct vcpu *v = current;
unsigned long *reg, eip = regs->eip;
u8 opcode, modrm_reg = 0, modrm_rm = 0, rep_prefix = 0, lock = 0, rex = 0;
@@ -1867,9 +1911,10 @@ static int emulate_privileged_op(struct cpu_user_regs
*regs)
void (*io_emul)(struct cpu_user_regs *) __attribute__((__regparm__(1)));
uint64_t val, msr_content;
- if ( !read_descriptor(regs->cs, v, regs,
- &code_base, &code_limit, &ar,
- _SEGMENT_CODE|_SEGMENT_S|_SEGMENT_DPL|_SEGMENT_P) )
+ if ( !read_descriptor_sel(regs->cs, x86_seg_cs, v, regs,
+ &code_base, &code_limit, &ar,
+ _SEGMENT_CODE|_SEGMENT_S|
+ _SEGMENT_DPL|_SEGMENT_P) )
goto fail;
op_default = op_bytes = (ar & (_SEGMENT_L|_SEGMENT_DB)) ? 4 : 2;
ad_default = ad_bytes = (ar & _SEGMENT_L) ? 8 : op_default;
@@ -1880,6 +1925,7 @@ static int emulate_privileged_op(struct cpu_user_regs
*regs)
/* emulating only opcodes not allowing SS to be default */
data_sel = read_segment_register(v, regs, ds);
+ which_sel = x86_seg_ds;
/* Legacy prefixes. */
for ( i = 0; i < 8; i++, rex == opcode || (rex = 0) )
@@ -1895,23 +1941,29 @@ static int emulate_privileged_op(struct cpu_user_regs
*regs)
continue;
case 0x2e: /* CS override */
data_sel = regs->cs;
+ which_sel = x86_seg_cs;
continue;
case 0x3e: /* DS override */
data_sel = read_segment_register(v, regs, ds);
+ which_sel = x86_seg_ds;
continue;
case 0x26: /* ES override */
data_sel = read_segment_register(v, regs, es);
+ which_sel = x86_seg_es;
continue;
case 0x64: /* FS override */
data_sel = read_segment_register(v, regs, fs);
+ which_sel = x86_seg_fs;
lm_ovr = lm_seg_fs;
continue;
case 0x65: /* GS override */
data_sel = read_segment_register(v, regs, gs);
+ which_sel = x86_seg_gs;
lm_ovr = lm_seg_gs;
continue;
case 0x36: /* SS override */
data_sel = regs->ss;
+ which_sel = x86_seg_ss;
continue;
case 0xf0: /* LOCK */
lock = 1;
@@ -1955,15 +2007,16 @@ static int emulate_privileged_op(struct cpu_user_regs
*regs)
if ( !(opcode & 2) )
{
data_sel = read_segment_register(v, regs, es);
+ which_sel = x86_seg_es;
lm_ovr = lm_seg_none;
}
if ( !(ar & _SEGMENT_L) )
{
- if ( !read_descriptor(data_sel, v, regs,
- &data_base, &data_limit, &ar,
- _SEGMENT_WR|_SEGMENT_S|_SEGMENT_DPL|
- _SEGMENT_P) )
+ if ( !read_descriptor_sel(data_sel, which_sel, v, regs,
+ &data_base, &data_limit, &ar,
+ _SEGMENT_WR|_SEGMENT_S|_SEGMENT_DPL|
+ _SEGMENT_P) )
goto fail;
if ( !(ar & _SEGMENT_S) ||
!(ar & _SEGMENT_P) ||
@@ -1993,9 +2046,9 @@ static int emulate_privileged_op(struct cpu_user_regs
*regs)
}
}
else
- read_descriptor(data_sel, v, regs,
- &data_base, &data_limit, &ar,
- 0);
+ read_descriptor_sel(data_sel, which_sel, v, regs,
+ &data_base, &data_limit, &ar,
+ 0);
data_limit = ~0UL;
ar = _SEGMENT_WR|_SEGMENT_S|_SEGMENT_DPL|_SEGMENT_P;
}
diff --git a/xen/include/asm-x86/desc.h b/xen/include/asm-x86/desc.h
index 354b889..041e9d3 100644
--- a/xen/include/asm-x86/desc.h
+++ b/xen/include/asm-x86/desc.h
@@ -38,7 +38,9 @@
#ifndef __ASSEMBLY__
-#define GUEST_KERNEL_RPL(d) (is_pv_32bit_domain(d) ? 1 : 3)
+/* PVH 32bitfixme : see emulate_gate_op call from do_general_protection */
+#define GUEST_KERNEL_RPL(d) ({ ASSERT(is_pv_domain(d)); \
+ is_pv_32bit_domain(d) ? 1 : 3; })
/* Fix up the RPL of a guest segment selector. */
#define __fixup_guest_selector(d, sel) \
--
1.7.9.5
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