From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Jim Mattson <jmattson@google.com>,
Maxim Levitsky <mlevitsk@redhat.com>,
Oliver Upton <oupton@google.com>, Peter Shier <pshier@google.com>
Subject: [PATCH v5 04/27] KVM: x86: Allow clearing RFLAGS.RF on forced emulation to test code #DBs
Date: Tue, 30 Aug 2022 23:15:51 +0000 [thread overview]
Message-ID: <20220830231614.3580124-5-seanjc@google.com> (raw)
In-Reply-To: <20220830231614.3580124-1-seanjc@google.com>
Extend force_emulation_prefix to an 'int' and use bit 1 as a flag to
indicate that KVM should clear RFLAGS.RF before emulating, e.g. to allow
tests to force emulation of code breakpoints in conjunction with MOV/POP
SS blocking, which is impossible without KVM intervention as VMX
unconditionally sets RFLAGS.RF on intercepted #UD.
Make the behavior controllable so that tests can also test RFLAGS.RF=1
(again in conjunction with code #DBs).
Note, clearing RFLAGS.RF won't create an infinite #DB loop as the guest's
IRET from the #DB handler will return to the instruction and not the
prefix, i.e. the restart won't force emulation.
Opportunistically convert the permissions to the preferred octal format.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fead0e8cd3e3..7403221c868e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -173,8 +173,13 @@ bool __read_mostly enable_vmware_backdoor = false;
module_param(enable_vmware_backdoor, bool, S_IRUGO);
EXPORT_SYMBOL_GPL(enable_vmware_backdoor);
-static bool __read_mostly force_emulation_prefix = false;
-module_param(force_emulation_prefix, bool, S_IRUGO);
+/*
+ * Flags to manipulate forced emulation behavior (any non-zero value will
+ * enable forced emulation).
+ */
+#define KVM_FEP_CLEAR_RFLAGS_RF BIT(1)
+static int __read_mostly force_emulation_prefix;
+module_param(force_emulation_prefix, int, 0444);
int __read_mostly pi_inject_timer = -1;
module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR);
@@ -7255,6 +7260,8 @@ int handle_ud(struct kvm_vcpu *vcpu)
kvm_read_guest_virt(vcpu, kvm_get_linear_rip(vcpu),
sig, sizeof(sig), &e) == 0 &&
memcmp(sig, kvm_emulate_prefix, sizeof(sig)) == 0) {
+ if (force_emulation_prefix & KVM_FEP_CLEAR_RFLAGS_RF)
+ kvm_set_rflags(vcpu, kvm_get_rflags(vcpu) & ~X86_EFLAGS_RF);
kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig));
emul_type = EMULTYPE_TRAP_UD_FORCED;
}
--
2.37.2.672.g94769d06f0-goog
next prev parent reply other threads:[~2022-08-30 23:17 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-30 23:15 [PATCH v5 00/27] KVM: x86: Event/exception fixes and cleanups Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 01/27] KVM: nVMX: Unconditionally purge queued/injected events on nested "exit" Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 02/27] KVM: VMX: Drop bits 31:16 when shoving exception error code into VMCS Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 03/27] KVM: x86: Don't check for code breakpoints when emulating on exception Sean Christopherson
2022-08-30 23:15 ` Sean Christopherson [this message]
2022-08-30 23:15 ` [PATCH v5 05/27] KVM: x86: Suppress code #DBs on Intel if MOV/POP SS blocking is active Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 06/27] KVM: nVMX: Treat General Detect #DB (DR7.GD=1) as fault-like Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 07/27] KVM: nVMX: Prioritize TSS T-flag #DBs over Monitor Trap Flag Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 08/27] KVM: x86: Treat #DBs from the emulator as fault-like (code and DR7.GD=1) Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 09/27] KVM: x86: Use DR7_GD macro instead of open coding check in emulator Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 10/27] KVM: nVMX: Ignore SIPI that arrives in L2 when vCPU is not in WFS Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 11/27] KVM: nVMX: Unconditionally clear mtf_pending on nested VM-Exit Sean Christopherson
2022-08-30 23:15 ` [PATCH v5 12/27] KVM: VMX: Inject #PF on ENCLS as "emulated" #PF Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 13/27] KVM: x86: Rename kvm_x86_ops.queue_exception to inject_exception Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 14/27] KVM: x86: Make kvm_queued_exception a properly named, visible struct Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 15/27] KVM: x86: Formalize blocking of nested pending exceptions Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 16/27] KVM: x86: Use kvm_queue_exception_e() to queue #DF Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 17/27] KVM: x86: Hoist nested event checks above event injection logic Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 18/27] KVM: x86: Evaluate ability to inject SMI/NMI/IRQ after potential VM-Exit Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 19/27] KVM: nVMX: Add a helper to identify low-priority #DB traps Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 20/27] KVM: nVMX: Document priority of all known events on Intel CPUs Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 21/27] KVM: x86: Morph pending exceptions to pending VM-Exits at queue time Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 22/27] KVM: x86: Treat pending TRIPLE_FAULT requests as pending exceptions Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 23/27] KVM: VMX: Update MTF and ICEBP comments to document KVM's subtle behavior Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 24/27] KVM: x86: Rename inject_pending_events() to kvm_check_and_inject_events() Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 25/27] KVM: selftests: Use uapi header to get VMX and SVM exit reasons/codes Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 26/27] KVM: selftests: Add an x86-only test to verify nested exception queueing Sean Christopherson
2022-08-30 23:16 ` [PATCH v5 27/27] KVM: x86: Allow force_emulation_prefix to be written without a reload Sean Christopherson
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