KVM: x86: Return emulator error if RDMSR/WRMSR emulation failed

The return value of emulator_{get|set}_mst_with_filter() is confused,
since msr access error and emulator error are mixed. Although,
KVM_MSR_RET_* doesn't conflict with X86EMUL_IO_NEEDED at present, it is
better to convert msr access error to emulator error if error value is
needed.

So move "r < 0" handling for wrmsr emulation into the set helper function,
then only X86EMUL_* is returned in the helper functions. Also add "r < 0"
check in the get helper function, although KVM doesn't return -errno
today, but assuming that will always hold true is unnecessarily risking.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: https://lore.kernel.org/r/09b2847fc3bcb8937fb11738f0ccf7be7f61d9dd.1661930557.git.houwenlong.hwl@antgroup.com
[sean: wrap changelog less aggressively]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 9367aaa..862498d 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3647,13 +3647,10 @@ static int em_wrmsr(struct x86_emulate_ctxt *ctxt)
                | ((u64)reg_read(ctxt, VCPU_REGS_RDX) << 32);
        r = ctxt->ops->set_msr_with_filter(ctxt, msr_index, msr_data);
 
-       if (r == X86EMUL_IO_NEEDED)
-               return r;
-
-       if (r > 0)
+       if (r == X86EMUL_PROPAGATE_FAULT)
                return emulate_gp(ctxt, 0);
 
-       return r < 0 ? X86EMUL_UNHANDLEABLE : X86EMUL_CONTINUE;
+       return r;
 }
 
 static int em_rdmsr(struct x86_emulate_ctxt *ctxt)
@@ -3664,15 +3661,14 @@ static int em_rdmsr(struct x86_emulate_ctxt *ctxt)
 
        r = ctxt->ops->get_msr_with_filter(ctxt, msr_index, &msr_data);
 
-       if (r == X86EMUL_IO_NEEDED)
-               return r;
-
-       if (r)
+       if (r == X86EMUL_PROPAGATE_FAULT)
                return emulate_gp(ctxt, 0);
 
-       *reg_write(ctxt, VCPU_REGS_RAX) = (u32)msr_data;
-       *reg_write(ctxt, VCPU_REGS_RDX) = msr_data >> 32;
-       return X86EMUL_CONTINUE;
+       if (r == X86EMUL_CONTINUE) {
+               *reg_write(ctxt, VCPU_REGS_RAX) = (u32)msr_data;
+               *reg_write(ctxt, VCPU_REGS_RDX) = msr_data >> 32;
+       }
+       return r;
 }
 
 static int em_store_sreg(struct x86_emulate_ctxt *ctxt, int segment)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ca04f4e..f5ee1ac 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7920,14 +7920,17 @@ static int emulator_get_msr_with_filter(struct x86_emulate_ctxt *ctxt,
        int r;
 
        r = kvm_get_msr_with_filter(vcpu, msr_index, pdata);
+       if (r < 0)
+               return X86EMUL_UNHANDLEABLE;
 
-       if (r && kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_RDMSR, 0,
-                                   complete_emulated_rdmsr, r)) {
-               /* Bounce to user space */
-               return X86EMUL_IO_NEEDED;
+       if (r) {
+               if (kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_RDMSR, 0,
+                                      complete_emulated_rdmsr, r))
+                       return X86EMUL_IO_NEEDED;
+               return X86EMUL_PROPAGATE_FAULT;
        }
 
-       return r;
+       return X86EMUL_CONTINUE;
 }
 
 static int emulator_set_msr_with_filter(struct x86_emulate_ctxt *ctxt,
@@ -7937,14 +7940,17 @@ static int emulator_set_msr_with_filter(struct x86_emulate_ctxt *ctxt,
        int r;
 
        r = kvm_set_msr_with_filter(vcpu, msr_index, data);
+       if (r < 0)
+               return X86EMUL_UNHANDLEABLE;
 
-       if (r && kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_WRMSR, data,
-                                   complete_emulated_msr_access, r)) {
-               /* Bounce to user space */
-               return X86EMUL_IO_NEEDED;
+       if (r) {
+               if (kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_WRMSR, data,
+                                      complete_emulated_msr_access, r))
+                       return X86EMUL_IO_NEEDED;
+               return X86EMUL_PROPAGATE_FAULT;
        }
 
-       return r;
+       return X86EMUL_CONTINUE;
 }
 
 static int emulator_get_msr(struct x86_emulate_ctxt *ctxt,