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 c39cf2c6e54523cced194fb56286af235e420148..5a0f64feafd424948b94f05a994ce8c2dbcecddb 100644 (file)
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -323,6 +323,17 @@ void free_vcpu_struct(struct vcpu *v)
     free_xenheap_page(v);
 }
 
+/* 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;
@@ -342,6 +353,8 @@ int vcpu_initialise(struct vcpu *v)
             return rc;
 
         vmce_init_vcpu(v);
+
+        arch_vcpu_regs_init(v);
     }
     else if ( (rc = xstate_alloc_save_area(v)) != 0 )
         return rc;

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 4cbb688c05b500c80bcc48b3731351ab8389fb31..611545f898fe8734aab013b58f8163b7dec312ff 100644 (file)
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3905,11 +3905,9 @@ 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.rflags = X86_EFLAGS_MBS;
-    v->arch.user_regs.rdx = 0x00000f00;
+
+    arch_vcpu_regs_init(v);
     v->arch.user_regs.rip = 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 61e69004653d468026ba26db98c379f92a18a3ec..ec81d788e36bd01e41d287bddf88a7b6d8219881 100644 (file)
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -633,6 +633,8 @@ 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);