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([2601:646:c200:1ef2:1d60:88a3:44d6:6b86]) by smtp.gmail.com with ESMTPSA id t22sm4337465pgm.18.2021.01.12.07.11.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Jan 2021 07:12:00 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions Date: Tue, 12 Jan 2021 07:11:58 -0800 Message-Id: <130DAF1C-06FC-4335-97AD-691B39A2C847@amacapital.net> References: <87eeiq8i7k.fsf@vitty.brq.redhat.com> Cc: Wei Huang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, joro@8bytes.org, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, jmattson@google.com, wanpengli@tencent.com, bsd@redhat.com, dgilbert@redhat.com, wei.huang2@amd.com, mlevitsk@redhat.com In-Reply-To: <87eeiq8i7k.fsf@vitty.brq.redhat.com> To: Vitaly Kuznetsov X-Mailer: iPhone Mail (18C66) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jan 12, 2021, at 4:15 AM, Vitaly Kuznetsov wrote:= >=20 > =EF=BB=BFWei Huang writes: >=20 >> From: Bandan Das >>=20 >> While running VM related instructions (VMRUN/VMSAVE/VMLOAD), some AMD >> CPUs check EAX against reserved memory regions (e.g. SMM memory on host) >> before checking VMCB's instruction intercept. If EAX falls into such >> memory areas, #GP is triggered before VMEXIT. This causes problem under >> nested virtualization. To solve this problem, KVM needs to trap #GP and >> check the instructions triggering #GP. For VM execution instructions, >> KVM emulates these instructions; otherwise it re-injects #GP back to >> guest VMs. >>=20 >> Signed-off-by: Bandan Das >> Co-developed-by: Wei Huang >> Signed-off-by: Wei Huang >> --- >> arch/x86/include/asm/kvm_host.h | 8 +- >> arch/x86/kvm/mmu.h | 1 + >> arch/x86/kvm/mmu/mmu.c | 7 ++ >> arch/x86/kvm/svm/svm.c | 157 +++++++++++++++++++------------- >> arch/x86/kvm/svm/svm.h | 8 ++ >> arch/x86/kvm/vmx/vmx.c | 2 +- >> arch/x86/kvm/x86.c | 37 +++++++- >> 7 files changed, 146 insertions(+), 74 deletions(-) >>=20 >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_h= ost.h >> index 3d6616f6f6ef..0ddc309f5a14 100644 >> --- a/arch/x86/include/asm/kvm_host.h >> +++ b/arch/x86/include/asm/kvm_host.h >> @@ -1450,10 +1450,12 @@ extern u64 kvm_mce_cap_supported; >> * due to an intercepted #UD (see EMULTYPE_TRAP_UD). >> * Used to test the full emulator from userspace. >> * >> - * EMULTYPE_VMWARE_GP - Set when emulating an intercepted #GP for VMware= >> + * EMULTYPE_PARAVIRT_GP - Set when emulating an intercepted #GP for VMwa= re >> * backdoor emulation, which is opt in via module param. >> * VMware backoor emulation handles select instructions >> - * and reinjects the #GP for all other cases. >> + * and reinjects #GP for all other cases. This also >> + * handles other cases where #GP condition needs to be >> + * handled and emulated appropriately >> * >> * EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in= which >> * case the CR2/GPA value pass on the stack is valid. >> @@ -1463,7 +1465,7 @@ extern u64 kvm_mce_cap_supported; >> #define EMULTYPE_SKIP (1 << 2) >> #define EMULTYPE_ALLOW_RETRY_PF (1 << 3) >> #define EMULTYPE_TRAP_UD_FORCED (1 << 4) >> -#define EMULTYPE_VMWARE_GP (1 << 5) >> +#define EMULTYPE_PARAVIRT_GP (1 << 5) >> #define EMULTYPE_PF (1 << 6) >>=20 >> int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type); >> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h >> index 581925e476d6..1a2fff4e7140 100644 >> --- a/arch/x86/kvm/mmu.h >> +++ b/arch/x86/kvm/mmu.h >> @@ -219,5 +219,6 @@ int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu); >>=20 >> int kvm_mmu_post_init_vm(struct kvm *kvm); >> void kvm_mmu_pre_destroy_vm(struct kvm *kvm); >> +bool kvm_is_host_reserved_region(u64 gpa); >=20 > Just a suggestion: "kvm_gpa_in_host_reserved()" maybe?=20 >=20 >>=20 >> #endif >> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c >> index 6d16481aa29d..c5c4aaf01a1a 100644 >> --- a/arch/x86/kvm/mmu/mmu.c >> +++ b/arch/x86/kvm/mmu/mmu.c >> @@ -50,6 +50,7 @@ >> #include >> #include >> #include >> +#include >> #include "trace.h" >>=20 >> extern bool itlb_multihit_kvm_mitigation; >> @@ -5675,6 +5676,12 @@ void kvm_mmu_slot_set_dirty(struct kvm *kvm, >> } >> EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty); >>=20 >> +bool kvm_is_host_reserved_region(u64 gpa) >> +{ >> + return e820__mbapped_raw_any(gpa-1, gpa+1, E820_TYPE_RESERVED); >> +} >=20 > While _e820__mapped_any()'s doc says '.. checks if any part of the > range is mapped ..' it seems to me that the real check is > [start, end) so we should use 'gpa' instead of 'gpa-1', no? Why do you need to check GPA at all?