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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 04/11] x86: Fix calculation of %dr6/7 reserved bits
The reserved bit calculations for %dr6 and %dr7 depend on whether the VM has
the Restricted Transnational Memory feature available.
Introduce adjust_dr{6,7}_rsvd() and replace the opencoded logic and constants
(except for DR_STATUS_RESERVED_ONE which is (mis)used elsewhere and will be
removed after future bugfixes). The use of these helpers in set_debugreg()
covers toolstack values for PV guests, but HVM guests need similar treatment.
The use of the guests cpuid policy is less than optimal in the create/restore
paths. However in such cases, the policy will be the guest maximum policy,
which will be more permissive with respect to the RTM feature.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
xen/arch/x86/domain.c | 5 ++++-
xen/arch/x86/hvm/hvm.c | 5 +++--
xen/arch/x86/traps.c | 17 +++++-----------
xen/include/asm-x86/debugreg.h | 44 ++++++++++++++++++++++++++++++++++++------
4 files changed, 50 insertions(+), 21 deletions(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 7ae9789..cee57a8 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -783,6 +783,7 @@ int arch_set_info_guest(
struct vcpu *v, vcpu_guest_context_u c)
{
struct domain *d = v->domain;
+ const struct cpuid_policy *cp = d->arch.cpuid;
unsigned long cr3_gfn;
struct page_info *cr3_page;
unsigned long flags, cr4;
@@ -894,8 +895,10 @@ int arch_set_info_guest(
if ( is_hvm_domain(d) )
{
- for ( i = 0; i < ARRAY_SIZE(v->arch.debugreg); ++i )
+ for ( i = 0; i < ARRAY_SIZE(v->arch.debugreg) - 2; ++i )
v->arch.debugreg[i] = c(debugreg[i]);
+ v->arch.debugreg[6] = adjust_dr6_rsvd(c(debugreg[6]), cp->feat.rtm);
+ v->arch.debugreg[7] = adjust_dr7_rsvd(c(debugreg[7]), cp->feat.rtm);
hvm_set_info_guest(v);
goto out;
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 10415e6..7fddae1 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -977,6 +977,7 @@ unsigned long hvm_cr4_guest_valid_bits(const struct domain
*d, bool restore)
static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
{
+ const struct cpuid_policy *cp = d->arch.cpuid;
int vcpuid;
struct vcpu *v;
struct hvm_hw_cpu ctxt;
@@ -1154,8 +1155,8 @@ static int hvm_load_cpu_ctxt(struct domain *d,
hvm_domain_context_t *h)
v->arch.debugreg[1] = ctxt.dr1;
v->arch.debugreg[2] = ctxt.dr2;
v->arch.debugreg[3] = ctxt.dr3;
- v->arch.debugreg[6] = ctxt.dr6;
- v->arch.debugreg[7] = ctxt.dr7;
+ v->arch.debugreg[6] = adjust_dr6_rsvd(ctxt.dr6, cp->feat.rtm);
+ v->arch.debugreg[7] = adjust_dr7_rsvd(ctxt.dr7, cp->feat.rtm);
v->arch.vgc_flags = VGCF_online;
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 6990c67..e9bfbc7 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2057,6 +2057,7 @@ void activate_debugregs(const struct vcpu *curr)
long set_debugreg(struct vcpu *v, unsigned int reg, unsigned long value)
{
struct vcpu *curr = current;
+ const struct cpuid_policy *cp = curr->domain->arch.cpuid;
switch ( reg )
{
@@ -2086,12 +2087,8 @@ long set_debugreg(struct vcpu *v, unsigned int reg,
unsigned long value)
if ( value != (uint32_t)value )
return -EINVAL;
- /*
- * DR6: Bits 4-11,16-31 reserved (set to 1).
- * Bit 12 reserved (set to 0).
- */
- value &= ~DR_STATUS_RESERVED_ZERO; /* reserved bits => 0 */
- value |= DR_STATUS_RESERVED_ONE; /* reserved bits => 1 */
+ value = adjust_dr6_rsvd(value, cp->feat.rtm);
+
if ( v == curr )
write_debugreg(6, value);
break;
@@ -2106,12 +2103,8 @@ long set_debugreg(struct vcpu *v, unsigned int reg,
unsigned long value)
if ( value != (uint32_t)value )
return -EINVAL;
- /*
- * DR7: Bit 10 reserved (set to 1).
- * Bits 11-12,14-15 reserved (set to 0).
- */
- value &= ~DR_CONTROL_RESERVED_ZERO; /* reserved bits => 0 */
- value |= DR_CONTROL_RESERVED_ONE; /* reserved bits => 1 */
+ value = adjust_dr7_rsvd(value, cp->feat.rtm);
+
/*
* Privileged bits:
* GD (bit 13): must be 0.
diff --git a/xen/include/asm-x86/debugreg.h b/xen/include/asm-x86/debugreg.h
index 8e6a656..8df566b 100644
--- a/xen/include/asm-x86/debugreg.h
+++ b/xen/include/asm-x86/debugreg.h
@@ -10,9 +10,18 @@
#define DR_STATUS 6
#define DR_CONTROL 7
-/* Define a few things for the status register. We can use this to determine
- which debugging register was responsible for the trap. The other bits
- are either reserved or not of interest to us. */
+/*
+ * DR6 status bits.
+ * N.B. For backwards compatibility, X86_DR6_RTM has inverted polarity.
+ */
+#define X86_DR6_B0 (1u << 0) /* Breakpoint 0 triggered */
+#define X86_DR6_B1 (1u << 1) /* Breakpoint 1 triggered */
+#define X86_DR6_B2 (1u << 2) /* Breakpoint 2 triggered */
+#define X86_DR6_B3 (1u << 3) /* Breakpoint 3 triggered */
+#define X86_DR6_BD (1u << 13) /* Debug register accessed */
+#define X86_DR6_BS (1u << 14) /* Single step */
+#define X86_DR6_BT (1u << 15) /* Task switch */
+#define X86_DR6_RTM (1u << 16) /* #DB/#BP in RTM region */
#define DR_TRAP0 (0x1) /* db0 */
#define DR_TRAP1 (0x2) /* db1 */
@@ -21,7 +30,6 @@
#define DR_STEP (0x4000) /* single-step */
#define DR_SWITCH (0x8000) /* task switch */
#define DR_NOT_RTM (0x10000) /* clear: #BP inside RTM region */
-#define DR_STATUS_RESERVED_ZERO (~0xffffeffful) /* Reserved, read as zero */
#define DR_STATUS_RESERVED_ONE 0xffff0ff0ul /* Reserved, read as one */
#define X86_DR6_DEFAULT 0xffff0ff0ul /* Default %dr6 value. */
@@ -63,8 +71,6 @@
We can slow the instruction pipeline for instructions coming via the
gdt or the ldt if we want to. I am not sure why this is an advantage */
-#define DR_CONTROL_RESERVED_ZERO (~0xffff27fful) /* Reserved, read as zero */
-#define DR_CONTROL_RESERVED_ONE (0x00000400ul) /* Reserved, read as one */
#define DR_LOCAL_EXACT_ENABLE (0x00000100ul) /* Local exact enable */
#define DR_GLOBAL_EXACT_ENABLE (0x00000200ul) /* Global exact enable */
#define DR_RTM_ENABLE (0x00000800ul) /* RTM debugging enable */
@@ -84,4 +90,30 @@
long set_debugreg(struct vcpu *, unsigned int reg, unsigned long value);
void activate_debugregs(const struct vcpu *);
+static inline unsigned long adjust_dr6_rsvd(unsigned long dr6, bool rtm)
+{
+ /*
+ * DR6: Bits 4-11,17-31 reserved (set to 1).
+ * Bit 16 reserved (set to 1) if RTM unavailable.
+ * Bit 12 reserved (set to 0).
+ */
+ dr6 |= 0xfffe0ff0 | (rtm ? 0 : X86_DR6_RTM);
+ dr6 &= 0xffffefff;
+
+ return dr6;
+}
+
+static inline unsigned long adjust_dr7_rsvd(unsigned long dr7, bool rtm)
+{
+ /*
+ * DR7: Bit 10 reserved (set to 1).
+ * Bit 11 reserved (set to 0) if RTM unavailable.
+ * Bits 12,14-15 reserved (set to 0).
+ */
+ dr7 |= 0x00000400;
+ dr7 &= 0xffff23ff & (rtm ? 0 : ~DR_RTM_ENABLE);
+
+ return dr7;
+}
+
#endif /* _X86_DEBUGREG_H */
--
2.1.4
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