From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Joerg Roedel" <joro@8bytes.org>,
"Jim Mattson" <jmattson@google.com>,
"Sean Christopherson" <sean.j.christopherson@intel.com>
Subject: [PATCH v2 5/5] x86: KVM: svm: remove hardcoded instruction length from intercepts
Date: Tue, 6 Aug 2019 08:01:50 +0200 [thread overview]
Message-ID: <20190806060150.32360-6-vkuznets@redhat.com> (raw)
In-Reply-To: <20190806060150.32360-1-vkuznets@redhat.com>
Various intercepts hard-code the respective instruction lengths to optimize
skip_emulated_instruction(): when next_rip is pre-set we skip
kvm_emulate_instruction(vcpu, EMULTYPE_SKIP). The optimization is, however,
incorrect: different (redundant) prefixes could be used to enlarge the
instruction. We can't really avoid decoding.
svm->next_rip is not used when CPU supports 'nrips' (X86_FEATURE_NRIPS)
feature: next RIP is provided in VMCB. The feature is not really new
(Opteron G3s had it already) and the change should have zero affect.
Remove manual svm->next_rip setting with hard-coded instruction lengths.
The only case where we now use svm->next_rip is EXIT_IOIO: the instruction
length is provided to us by hardware.
Reported-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/svm.c | 15 ++-------------
1 file changed, 2 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 793a60461abe..dce215250d1f 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2905,13 +2905,11 @@ static int nop_on_interception(struct vcpu_svm *svm)
static int halt_interception(struct vcpu_svm *svm)
{
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 1;
return kvm_emulate_halt(&svm->vcpu);
}
static int vmmcall_interception(struct vcpu_svm *svm)
{
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
return kvm_emulate_hypercall(&svm->vcpu);
}
@@ -3699,7 +3697,6 @@ static int vmload_interception(struct vcpu_svm *svm)
nested_vmcb = map.hva;
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
ret = kvm_skip_emulated_instruction(&svm->vcpu);
nested_svm_vmloadsave(nested_vmcb, svm->vmcb);
@@ -3726,7 +3723,6 @@ static int vmsave_interception(struct vcpu_svm *svm)
nested_vmcb = map.hva;
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
ret = kvm_skip_emulated_instruction(&svm->vcpu);
nested_svm_vmloadsave(svm->vmcb, nested_vmcb);
@@ -3740,8 +3736,8 @@ static int vmrun_interception(struct vcpu_svm *svm)
if (nested_svm_check_permissions(svm))
return 1;
- /* Save rip after vmrun instruction */
- kvm_rip_write(&svm->vcpu, kvm_rip_read(&svm->vcpu) + 3);
+ if (!kvm_skip_emulated_instruction(&svm->vcpu))
+ return 1;
if (!nested_svm_vmrun(svm))
return 1;
@@ -3777,7 +3773,6 @@ static int stgi_interception(struct vcpu_svm *svm)
if (vgif_enabled(svm))
clr_intercept(svm, INTERCEPT_STGI);
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
ret = kvm_skip_emulated_instruction(&svm->vcpu);
kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
@@ -3793,7 +3788,6 @@ static int clgi_interception(struct vcpu_svm *svm)
if (nested_svm_check_permissions(svm))
return 1;
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
ret = kvm_skip_emulated_instruction(&svm->vcpu);
disable_gif(svm);
@@ -3818,7 +3812,6 @@ static int invlpga_interception(struct vcpu_svm *svm)
/* Let's treat INVLPGA the same as INVLPG (can be optimized!) */
kvm_mmu_invlpg(vcpu, kvm_rax_read(&svm->vcpu));
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
return kvm_skip_emulated_instruction(&svm->vcpu);
}
@@ -3841,7 +3834,6 @@ static int xsetbv_interception(struct vcpu_svm *svm)
u32 index = kvm_rcx_read(&svm->vcpu);
if (kvm_set_xcr(&svm->vcpu, index, new_bv) == 0) {
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
return kvm_skip_emulated_instruction(&svm->vcpu);
}
@@ -3918,7 +3910,6 @@ static int task_switch_interception(struct vcpu_svm *svm)
static int cpuid_interception(struct vcpu_svm *svm)
{
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
return kvm_emulate_cpuid(&svm->vcpu);
}
@@ -4248,7 +4239,6 @@ static int rdmsr_interception(struct vcpu_svm *svm)
kvm_rax_write(&svm->vcpu, msr_info.data & 0xffffffff);
kvm_rdx_write(&svm->vcpu, msr_info.data >> 32);
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
return kvm_skip_emulated_instruction(&svm->vcpu);
}
}
@@ -4454,7 +4444,6 @@ static int wrmsr_interception(struct vcpu_svm *svm)
return 1;
} else {
trace_kvm_msr_write(ecx, data);
- svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
return kvm_skip_emulated_instruction(&svm->vcpu);
}
}
--
2.20.1
next prev parent reply other threads:[~2019-08-06 6:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 6:01 [PATCH v2 0/5] x86: KVM: svm: get rid of hardcoded instructions lengths Vitaly Kuznetsov
2019-08-06 6:01 ` [PATCH v2 1/5] x86: KVM: svm: don't pretend to advance RIP in case wrmsr_interception() results in #GP Vitaly Kuznetsov
2019-08-06 15:29 ` Sean Christopherson
2019-08-06 6:01 ` [PATCH v2 2/5] x86: KVM: svm: avoid flooding logs when skip_emulated_instruction() fails Vitaly Kuznetsov
2019-08-06 15:40 ` Sean Christopherson
2019-08-07 11:17 ` Vitaly Kuznetsov
2019-08-06 6:01 ` [PATCH v2 3/5] x86: KVM: clear interrupt shadow on EMULTYPE_SKIP Vitaly Kuznetsov
2019-08-06 15:45 ` Sean Christopherson
2019-08-06 6:01 ` [PATCH v2 4/5] x86: KVM: add xsetbv to the emulator Vitaly Kuznetsov
2019-08-06 6:01 ` Vitaly Kuznetsov [this message]
2019-08-06 16:11 ` [PATCH v2 5/5] x86: KVM: svm: remove hardcoded instruction length from intercepts Sean Christopherson
2019-08-07 11:14 ` Vitaly Kuznetsov
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