[PATCH 5.11 098/601] KVM: x86: Remove emulators broken checks on CR0/CR3/CR4 loads

Greg Kroah-Hartman
2021-05-12T17:02:21Z

From: Sean Christopherson <seanjc@google.com>

commit d0fe7b6404408835ed60232cb3bf28324b2f95db upstream.

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the checks are redundant, outdated, and in the case of SEV's C-bit,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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/emulate.c | 80 +------------------------------------------------
1 file changed, 3 insertions(+), 77 deletions(-)

--- 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_emul
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
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,