KVM: x86: Remove emulator's broken checks on CR0/CR3/CR4 loads

Remove the emulator's checks for illegal CR0, CR3, and CR4 values, as
the checks are redundant, outdated, and in the case of SEV's C-bit,
broken.  The emulator manually calculates MAXPHYADDR from CPUID and
neglects to mask off the C-bit.  For all other checks, kvm_set_cr*() are
a superset of the emulator checks, e.g. see CR4.LA57.

Fixes: a780a3ea6282 ("KVM: X86: Fix reserved bits check for MOV to CR3")
Cc: Babu Moger <babu.moger@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210422022128.3464144-2-seanjc@google.com>
Cc: stable@vger.kernel.org
[Unify check_cr_read and check_cr_write. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index f7970ba..abd9a4d 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4220,7 +4220,7 @@ static bool valid_cr(int nr)
        }
 }
 
-static int check_cr_read(struct x86_emulate_ctxt *ctxt)
+static int check_cr_access(struct x86_emulate_ctxt *ctxt)
 {
        if (!valid_cr(ctxt->modrm_reg))
                return emulate_ud(ctxt);
@@ -4228,80 +4228,6 @@ static int check_cr_read(struct x86_emulate_ctxt *ctxt)
        return X86EMUL_CONTINUE;
 }
 
-static int check_cr_write(struct x86_emulate_ctxt *ctxt)
-{
-       u64 new_val = ctxt->src.val64;
-       int cr = ctxt->modrm_reg;
-       u64 efer = 0;
-
-       static u64 cr_reserved_bits[] = {
-               0xffffffff00000000ULL,
-               0, 0, 0, /* CR3 checked later */
-               CR4_RESERVED_BITS,
-               0, 0, 0,
-               CR8_RESERVED_BITS,
-       };
-
-       if (!valid_cr(cr))
-               return emulate_ud(ctxt);
-
-       if (new_val & cr_reserved_bits[cr])
-               return emulate_gp(ctxt, 0);
-
-       switch (cr) {
-       case 0: {
-               u64 cr4;
-               if (((new_val & X86_CR0_PG) && !(new_val & X86_CR0_PE)) ||
-                   ((new_val & X86_CR0_NW) && !(new_val & X86_CR0_CD)))
-                       return emulate_gp(ctxt, 0);
-
-               cr4 = ctxt->ops->get_cr(ctxt, 4);
-               ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
-
-               if ((new_val & X86_CR0_PG) && (efer & EFER_LME) &&
-                   !(cr4 & X86_CR4_PAE))
-                       return emulate_gp(ctxt, 0);
-
-               break;
-               }
-       case 3: {
-               u64 rsvd = 0;
-
-               ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
-               if (efer & EFER_LMA) {
-                       u64 maxphyaddr;
-                       u32 eax, ebx, ecx, edx;
-
-                       eax = 0x80000008;
-                       ecx = 0;
-                       if (ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx,
-                                                &edx, true))
-                               maxphyaddr = eax & 0xff;
-                       else
-                               maxphyaddr = 36;
-                       rsvd = rsvd_bits(maxphyaddr, 63);
-                       if (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_PCIDE)
-                               rsvd &= ~X86_CR3_PCID_NOFLUSH;
-               }
-
-               if (new_val & rsvd)
-                       return emulate_gp(ctxt, 0);
-
-               break;
-               }
-       case 4: {
-               ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
-
-               if ((efer & EFER_LMA) && !(new_val & X86_CR4_PAE))
-                       return emulate_gp(ctxt, 0);
-
-               break;
-               }
-       }
-
-       return X86EMUL_CONTINUE;
-}
-
 static int check_dr7_gd(struct x86_emulate_ctxt *ctxt)
 {
        unsigned long dr7;
@@ -4841,10 +4767,10 @@ static const struct opcode twobyte_table[256] = {
        D(ImplicitOps | ModRM | SrcMem | NoAccess), /* 8 * reserved NOP */
        D(ImplicitOps | ModRM | SrcMem | NoAccess), /* NOP + 7 * reserved NOP */
        /* 0x20 - 0x2F */
-       DIP(ModRM | DstMem | Priv | Op3264 | NoMod, cr_read, check_cr_read),
+       DIP(ModRM | DstMem | Priv | Op3264 | NoMod, cr_read, check_cr_access),
        DIP(ModRM | DstMem | Priv | Op3264 | NoMod, dr_read, check_dr_read),
        IIP(ModRM | SrcMem | Priv | Op3264 | NoMod, em_cr_write, cr_write,
-                                               check_cr_write),
+                                               check_cr_access),
        IIP(ModRM | SrcMem | Priv | Op3264 | NoMod, em_dr_write, dr_write,
                                                check_dr_write),
        N, N, N, N,