From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wanpeng Li Subject: Re: [PATCH v2 3/3] KVM: x86: #GP when attempts to write reserved bits of Variable Range MTRRs Date: Mon, 1 Sep 2014 08:22:08 +0800 Message-ID: <20140901002208.GA11180@kernel> References: <1408439080-57721-1-git-send-email-wanpeng.li@linux.intel.com> <1408439080-57721-3-git-send-email-wanpeng.li@linux.intel.com> <5400AEBA.2080405@redhat.com> Reply-To: Wanpeng Li Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Marcelo Tosatti , Gleb Natapov , Zhang Yang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Paolo Bonzini , Jan Kiszka Return-path: Received: from mga11.intel.com ([192.55.52.93]:59231 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752177AbaIAAU2 (ORCPT ); Sun, 31 Aug 2014 20:20:28 -0400 Content-Disposition: inline In-Reply-To: <5400AEBA.2080405@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Fri, Aug 29, 2014 at 06:47:54PM +0200, Paolo Bonzini wrote: >Il 19/08/2014 11:04, Wanpeng Li ha scritto: >> Section 11.11.2.3 of the SDM mentions "All other bits in the IA32_MTRR_PHYSBASEn >> and IA32_MTRR_PHYSMASKn registers are reserved; the processor generates a >> general-protection exception(#GP) if software attempts to write to them". This >> patch do it in kvm. >> >> Signed-off-by: Wanpeng Li > >This breaks if the guest maxphyaddr is higher than the host's (which >sometimes happens depending on your hardware and how QEMU is >configured). > >You need to use cpuid_maxphyaddr, like this > >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >index a375dfc42f6a..916e89515210 100644 >--- a/arch/x86/kvm/x86.c >+++ b/arch/x86/kvm/x86.c >@@ -1726,7 +1726,7 @@ static bool valid_mtrr_type(unsigned t) > static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data) > { > int i; >- u64 mask = 0; >+ u64 mask; > > if (!msr_mtrr_valid(msr)) > return false; >@@ -1750,8 +1750,7 @@ static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data) > /* variable MTRRs */ > WARN_ON(!(msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR)); > >- for (i = 63; i > boot_cpu_data.x86_phys_bits; i--) >- mask |= (1ULL << i); >+ mask = (~0ULL) << cpuid_maxphyaddr(vcpu); > if ((msr & 1) == 0) { > /* MTRR base */ > if (!valid_mtrr_type(data & 0xff)) > > Got it, thanks Paolo and Jan. Regards, Wanpeng Li >Jan, can you see if this patch fixes the SeaBIOS triple fault you reported? > >Paolo > >> --- >> arch/x86/kvm/x86.c | 18 +++++++++++++++--- >> 1 file changed, 15 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index fb3ea7a..b85da5f 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -1726,6 +1726,7 @@ static bool valid_mtrr_type(unsigned t) >> static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data) >> { >> int i; >> + u64 mask = 0; >> >> if (!msr_mtrr_valid(msr)) >> return false; >> @@ -1749,10 +1750,21 @@ static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data) >> /* variable MTRRs */ >> WARN_ON(!(msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR)); >> >> - if ((msr & 1) == 0) >> + for (i = 63; i > boot_cpu_data.x86_phys_bits; i--) >> + mask |= (1ULL << i); >> + if ((msr & 1) == 0) { >> /* MTRR base */ >> - return valid_mtrr_type(data & 0xff); >> - /* MTRR mask */ >> + if (!valid_mtrr_type(data & 0xff)) >> + return false; >> + mask |= 0xf00; >> + } else >> + /* MTRR mask */ >> + mask |= 0x7ff; >> + if (data & mask) { >> + kvm_inject_gp(vcpu, 0); >> + return false; >> + } >> + >> return true; >> } >> >>