x86/domain: Initialise vcpu debug registers correctly

In particular, initialising %dr6 with the value 0 is buggy, because on
hardware supporting Transactional Memory, it will cause the sticky RTM bit to
be asserted, even though a debug exception from a transaction hasn't actually
been observed.

Introduce arch_vcpu_regs_init() to set various architectural defaults, and
reuse this in the hvm_vcpu_reset_state() path.

Architecturally, %edx's init state contains the processors model information,
and 0xf looks to be a remnant of the old Intel processors.  We clearly have no
software which cares, seeing as it is wrong for the last decade's worth of
Intel hardware and for all other vendors, so lets use the value 0 for
simplicity.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
x86/domain: Fix build with GCC 4.3.x

GCC 4.3.x can't initialise the user_regs structure like this.

Reported-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
master commit: dfba4d2e91f63a8f40493c4fc2db03fd8287f6cb
master date: 2018-10-24 14:43:05 +0100
master commit: 0a1fa635029d100d4b6b7eddb31d49603217cab7
master date: 2018-10-30 13:26:21 +0000

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 2f4398657635de41ec3bf75e9e6e9e4414c22050..408fc0bc132436126f58e0fd0a097c4dc00510d8 100644 (file)
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -499,6 +499,17 @@ int switch_compat(struct domain *d)
     return rc;
 }
 
+/* Initialise various registers to their architectural INIT/RESET state. */
+void arch_vcpu_regs_init(struct vcpu *v)
+{
+    memset(&v->arch.user_regs, 0, sizeof(v->arch.user_regs));
+    v->arch.user_regs.eflags = X86_EFLAGS_MBS;
+
+    memset(v->arch.debugreg, 0, sizeof(v->arch.debugreg));
+    v->arch.debugreg[6] = X86_DR6_DEFAULT;
+    v->arch.debugreg[7] = X86_DR7_DEFAULT;
+}
+
 int vcpu_initialise(struct vcpu *v)
 {
     struct domain *d = v->domain;
@@ -518,6 +529,8 @@ int vcpu_initialise(struct vcpu *v)
             return rc;
 
         vmce_init_vcpu(v);
+
+        arch_vcpu_regs_init(v);
     }
 
     spin_lock_init(&v->arch.vpmu.vpmu_lock);

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 4cf9b52c6216931a259399f07ce97148732b1aba..ca64f6a5df6a415e4a2b7ddec2ef27e5a2978fab 100644 (file)
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4703,11 +4703,9 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, uint16_t ip)
     }
 
     v->arch.vgc_flags = VGCF_online;
-    memset(&v->arch.user_regs, 0, sizeof(v->arch.user_regs));
-    v->arch.user_regs.eflags = X86_EFLAGS_MBS;
-    v->arch.user_regs.edx = 0x00000f00;
+
+    arch_vcpu_regs_init(v);
     v->arch.user_regs.eip = ip;
-    memset(&v->arch.debugreg, 0, sizeof(v->arch.debugreg));
 
     v->arch.hvm_vcpu.guest_cr[0] = X86_CR0_ET;
     hvm_update_guest_cr(v, 0);

diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index c1378ea539467b768ab50bc5fa6c676eec1febde..e7abaadcbce97f935a894cbecb6668996714c270 100644 (file)
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -673,6 +673,8 @@ static inline void free_vcpu_guest_context(struct vcpu_guest_context *vgc)
     vfree(vgc);
 }
 
+void arch_vcpu_regs_init(struct vcpu *v);
+
 struct vcpu_hvm_context;
 int arch_set_info_hvm_guest(struct vcpu *v, const struct vcpu_hvm_context *ctx);