x86/vmx: Don't leak host syscall MSR state into HVM guests

hvm_hw_cpu->msr_flags is in fact the VMX dirty bitmap of MSRs needing to be
restored when switching into guest context.  It should never have been part of
the migration state to start with, and Xen must not make any decisions based
on the value seen during restore.

Identify it as obsolete in the header files, consistently save it as zero and
ignore it on restore.

The MSRs must be considered dirty during VMCS creation to cause the proper
defaults of 0 to be visible to the guest.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
master commit: 2f1add6e1c8789d979daaafa3d80ddc1bc375783
master date: 2017-02-21 11:06:39 +0000

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 41392a12bde951c5362c8bc39fdf4f0a90a5bf0e..b0715e633ac05930c8e810ef5a1307d85d30dbae 100644 (file)
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -356,7 +356,7 @@ static void svm_save_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data)
     data->msr_cstar        = vmcb->cstar;
     data->msr_syscall_mask = vmcb->sfmask;
     data->msr_efer         = v->arch.hvm_vcpu.guest_efer;
-    data->msr_flags        = -1ULL;
+    data->msr_flags        = 0;
 }
 
 

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 6131a239cafd4075fd10db9000fc8817b846ce9f..ea2c665b873e2c0c229a8a56520326e39bbc13d6 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1124,6 +1124,9 @@ static int construct_vmcs(struct vcpu *v)
             vmx_disable_intercept_for_msr(v, MSR_IA32_BNDCFGS, MSR_TYPE_R | MSR_TYPE_W);
     }
 
+    /* All guest MSR state is dirty. */
+    v->arch.hvm_vmx.msr_state.flags = ((1u << VMX_MSR_COUNT) - 1);
+
     /* I/O access bitmap. */
     __vmwrite(IO_BITMAP_A, __pa(d->arch.hvm_domain.io_bitmap));
     __vmwrite(IO_BITMAP_B, __pa(d->arch.hvm_domain.io_bitmap) + PAGE_SIZE);

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 3d19b76f70ab2cf7b28206b8c4734d993aa5948f..9d958e882dcf5a3624756e25286b3937c9ce9a6d 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -737,13 +737,12 @@ static int vmx_vmcs_restore(struct vcpu *v, struct hvm_hw_cpu *c)
 static void vmx_save_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data)
 {
     struct vmx_msr_state *guest_state = &v->arch.hvm_vmx.msr_state;
-    unsigned long guest_flags = guest_state->flags;
 
     data->shadow_gs = v->arch.hvm_vmx.shadow_gs;
     data->msr_cstar = v->arch.hvm_vmx.cstar;
 
     /* save msrs */
-    data->msr_flags        = guest_flags;
+    data->msr_flags        = 0;
     data->msr_lstar        = guest_state->msrs[VMX_INDEX_MSR_LSTAR];
     data->msr_star         = guest_state->msrs[VMX_INDEX_MSR_STAR];
     data->msr_syscall_mask = guest_state->msrs[VMX_INDEX_MSR_SYSCALL_MASK];
@@ -754,7 +753,7 @@ static void vmx_load_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data)
     struct vmx_msr_state *guest_state = &v->arch.hvm_vmx.msr_state;
 
     /* restore msrs */
-    guest_state->flags = data->msr_flags & 7;
+    guest_state->flags = ((1u << VMX_MSR_COUNT) - 1);
     guest_state->msrs[VMX_INDEX_MSR_LSTAR]        = data->msr_lstar;
     guest_state->msrs[VMX_INDEX_MSR_STAR]         = data->msr_star;
     guest_state->msrs[VMX_INDEX_MSR_SYSCALL_MASK] = data->msr_syscall_mask;

diff --git a/xen/include/public/arch-x86/hvm/save.h b/xen/include/public/arch-x86/hvm/save.h
index 8d73b51f061e1ad4e5c725d2302a918c635cee6e..419a3b23d44e73f155769ade82a07b20ca73391e 100644 (file)
--- a/xen/include/public/arch-x86/hvm/save.h
+++ b/xen/include/public/arch-x86/hvm/save.h
@@ -135,7 +135,7 @@ struct hvm_hw_cpu {
     uint64_t shadow_gs;
 
     /* msr content saved/restored. */
-    uint64_t msr_flags;
+    uint64_t msr_flags; /* Obsolete, ignored. */
     uint64_t msr_lstar;
     uint64_t msr_star;
     uint64_t msr_cstar;
@@ -249,7 +249,7 @@ struct hvm_hw_cpu_compat {
     uint64_t shadow_gs;
 
     /* msr content saved/restored. */
-    uint64_t msr_flags;
+    uint64_t msr_flags; /* Obsolete, ignored. */
     uint64_t msr_lstar;
     uint64_t msr_star;
     uint64_t msr_cstar;