The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From d0fe7b6404408835ed60232cb3bf28324b2f95db Mon Sep 17 00:00:00 2001
From: Sean Christopherson seanjc@google.com Date: Wed, 21 Apr 2021 19:21:20 -0700 Subject: [PATCH] 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Remove the emulator's checks for illegal CR0, CR3, and CR4 values, as the checks are redundant, outdated, and in the case of SEV's C-bit, broken.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 f7970ba6219f..abd9a4db11a8 100644 --- 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,