[PATCH] KVM: x86: dynamically allocate large struct in em_fxrstor

[Nick Desaulniers]

Fixes the warning:

arch/x86/kvm/emulate.c:4018:12: warning: stack frame size of 1080 bytes in
function
      'em_fxrstor' [-Wframe-larger-than=]
static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
           ^

Found with CONFIG_FRAME_WARN set to 1024.

Signed-off-by: Nick Desaulniers <nick.desaulni...@gmail.com>
---
 arch/x86/kvm/emulate.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 0816ab2e8adc..1d7c9ceeff56 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4017,30 +4017,38 @@ static int fxrstor_fixup(struct x86_emulate_ctxt *ctxt,
 
 static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
 {
-       struct fxregs_state fx_state;
+       struct fxregs_state *fx_state;
        int rc;
 
        rc = check_fxsr(ctxt);
        if (rc != X86EMUL_CONTINUE)
                return rc;
 
-       rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
+       fx_state = kmalloc(sizeof(*fx_state), GFP_KERNEL);
+       if (!fx_state)
+               return -ENOMEM;
+
+       rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, fx_state, 512);
        if (rc != X86EMUL_CONTINUE)
-               return rc;
+               goto out;
 
-       if (fx_state.mxcsr >> 16)
-               return emulate_gp(ctxt, 0);
+       if (fx_state->mxcsr >> 16) {
+               rc = emulate_gp(ctxt, 0);
+               goto out;
+       }
 
        ctxt->ops->get_fpu(ctxt);
 
        if (ctxt->mode < X86EMUL_MODE_PROT64)
-               rc = fxrstor_fixup(ctxt, &fx_state);
+               rc = fxrstor_fixup(ctxt, fx_state);
 
        if (rc == X86EMUL_CONTINUE)
-               rc = asm_safe("fxrstor %[fx]", : [fx] "m"(fx_state));
+               rc = asm_safe("fxrstor %[fx]", : [fx] "m"(*fx_state));
 
        ctxt->ops->put_fpu(ctxt);
 
+out:
+       kfree(fx_state);
        return rc;
 }
 
-- 
2.11.0