diff options
| author | Sean Christopherson | 2022-07-15 23:00:13 +0000 |
|---|---|---|
| committer | Paolo Bonzini | 2022-07-28 13:22:20 -0400 |
| commit | 94bda2f4cd868046094351b06b87d7d1053e990d (patch) | |
| tree | 589bc00c4153f613d418ef544661f09b05fffbc4 /arch/x86/kvm | |
| parent | 01e69cef63f88d809181f62f03a01d7295f2d5a4 (diff) | |
KVM: x86: Reject loading KVM if host.PAT[0] != WB
Reject KVM if entry '0' in the host's IA32_PAT MSR is not programmed to
writeback (WB) memtype. KVM subtly relies on IA32_PAT entry '0' to be
programmed to WB by leaving the PAT bits in shadow paging and NPT SPTEs
as '0'. If something other than WB is in PAT[0], at _best_ guests will
suffer very poor performance, and at worst KVM will crash the system by
breaking cache-coherency expecations (e.g. using WC for guest memory).
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220715230016.3762909-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/x86.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f389691d8c04..12199c40f2bc 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9141,6 +9141,7 @@ static struct notifier_block pvclock_gtod_notifier = { int kvm_arch_init(void *opaque) { struct kvm_x86_init_ops *ops = opaque; + u64 host_pat; int r; if (kvm_x86_ops.hardware_enable) { @@ -9179,6 +9180,20 @@ int kvm_arch_init(void *opaque) goto out; } + /* + * KVM assumes that PAT entry '0' encodes WB memtype and simply zeroes + * the PAT bits in SPTEs. Bail if PAT[0] is programmed to something + * other than WB. Note, EPT doesn't utilize the PAT, but don't bother + * with an exception. PAT[0] is set to WB on RESET and also by the + * kernel, i.e. failure indicates a kernel bug or broken firmware. + */ + if (rdmsrl_safe(MSR_IA32_CR_PAT, &host_pat) || + (host_pat & GENMASK(2, 0)) != 6) { + pr_err("kvm: host PAT[0] is not WB\n"); + r = -EIO; + goto out; + } + r = -ENOMEM; x86_emulator_cache = kvm_alloc_emulator_cache(); |