[Xen-changelog] [xen stable-4.8] x86/domain: Initialise vcpu debug registers correctly

[patchbot@xxxxxxx]

commit 64fd42fbcb3928454056ef2663d5b248cd8c3a84
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Nov 5 16:17:26 2018 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Nov 5 16:17:26 2018 +0100

    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    
    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@xxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: dfba4d2e91f63a8f40493c4fc2db03fd8287f6cb
    master date: 2018-10-24 14:43:05 +0100
    master commit: 0a1fa635029d100d4b6b7eddb31d49603217cab7
    master date: 2018-10-30 13:26:21 +0000
---
 xen/arch/x86/domain.c        | 13 +++++++++++++
 xen/arch/x86/hvm/hvm.c       |  6 ++----
 xen/include/asm-x86/domain.h |  2 ++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 2f43986576..408fc0bc13 100644
--- 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 4cf9b52c62..ca64f6a5df 100644
--- 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 c1378ea539..e7abaadcbc 100644
--- 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);
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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