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

[patchbot@xxxxxxx]

commit dfba4d2e91f63a8f40493c4fc2db03fd8287f6cb
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon May 28 14:18:17 2018 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Oct 24 14:43:05 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>
---
 xen/arch/x86/domain.c        | 14 ++++++++++++++
 xen/arch/x86/hvm/hvm.c       |  6 ++----
 xen/include/asm-x86/domain.h |  2 ++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 9371efc8c7..6f19fbfe69 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -323,6 +323,18 @@ 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)
+{
+    v->arch.user_regs = (typeof(v->arch.user_regs)){
+        .rflags = 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 arch_vcpu_create(struct vcpu *v)
 {
     struct domain *d = v->domain;
@@ -342,6 +354,8 @@ int arch_vcpu_create(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 af13de3745..56a8de8034 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3850,11 +3850,9 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, 
uint16_t ip)
     vcpu_setup_fpu(v, v->arch.xsave_area, NULL, FCW_RESET);
 
     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.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 e7b82279e7..503f8ff2de 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -669,6 +669,8 @@ 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#master

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