[PATCH 8/9] x86/vmx: Support removing MSRs from the host/guest load/save lists

[Andrew Cooper <andrew.cooper3@citrix.com>]

Up until this point, the MSR load/save lists have only ever accumulated
content.  Introduce vmx_del_msr() as a companion to vmx_add_msr().

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Jun Nakajima <jun.nakajima@intel.com>
CC: Kevin Tian <kevin.tian@intel.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/hvm/vmx/vmcs.c        | 68 ++++++++++++++++++++++++++++++++++++++
 xen/include/asm-x86/hvm/vmx/vmcs.h |  1 +
 2 files changed, 69 insertions(+)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 7bf19a0..e1a8f95 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1465,6 +1465,74 @@ int vmx_add_msr(struct vcpu *v, uint32_t msr, uint64_t val,
     return rc;
 }
 
+int vmx_del_msr(struct vcpu *v, uint32_t msr, enum vmx_msr_list_type type)
+{
+    struct arch_vmx_struct *arch_vmx = &v->arch.hvm_vmx;
+    struct vmx_msr_entry *start = NULL, *ent, *end;
+    unsigned int substart, subend, total;
+
+    ASSERT(v == current || !vcpu_runnable(v));
+
+    switch ( type )
+    {
+    case VMX_MSR_HOST:
+        start    = arch_vmx->host_msr_area;
+        substart = 0;
+        subend   = arch_vmx->host_msr_count;
+        total    = subend;
+        break;
+
+    case VMX_MSR_GUEST:
+        start    = arch_vmx->msr_area;
+        substart = 0;
+        subend   = arch_vmx->msr_save_count;
+        total    = arch_vmx->msr_load_count;
+        break;
+
+    case VMX_MSR_GUEST_LOADONLY:
+        start    = arch_vmx->msr_area;
+        substart = arch_vmx->msr_save_count;
+        subend   = arch_vmx->msr_load_count;
+        total    = subend;
+        break;
+
+    default:
+        ASSERT_UNREACHABLE();
+    }
+
+    if ( !start )
+        return -ESRCH;
+
+    end = start + total;
+    ent = locate_msr_entry(start + substart, start + subend, msr);
+
+    if ( (ent == end) || (ent->index != msr) )
+        return -ESRCH;
+
+    memmove(ent, ent + 1, sizeof(*ent) * (end - ent));
+
+    vmx_vmcs_enter(v);
+
+    switch ( type )
+    {
+    case VMX_MSR_HOST:
+        __vmwrite(VM_EXIT_MSR_LOAD_COUNT, arch_vmx->host_msr_count--);
+        break;
+
+    case VMX_MSR_GUEST:
+        __vmwrite(VM_EXIT_MSR_STORE_COUNT, arch_vmx->msr_save_count--);
+
+        /* Fallthrough */
+    case VMX_MSR_GUEST_LOADONLY:
+        __vmwrite(VM_ENTRY_MSR_LOAD_COUNT, arch_vmx->msr_load_count--);
+        break;
+    }
+
+    vmx_vmcs_exit(v);
+
+    return 0;
+}
+
 void vmx_set_eoi_exit_bitmap(struct vcpu *v, u8 vector)
 {
     if ( !test_and_set_bit(vector, v->arch.hvm_vmx.eoi_exit_bitmap) )
diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h b/xen/include/asm-x86/hvm/vmx/vmcs.h
index b0fccd2..cfd174c 100644
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
@@ -548,6 +548,7 @@ enum vmx_msr_list_type {
 
 int vmx_add_msr(struct vcpu *v, uint32_t msr, uint64_t val,
                 enum vmx_msr_list_type type);
+int vmx_del_msr(struct vcpu *v, uint32_t msr, enum vmx_msr_list_type type);
 
 static inline int vmx_add_guest_msr(struct vcpu *v, uint32_t msr, uint64_t val)
 {
-- 
2.1.4


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