[x86] Backport KVM nested VMX fixes from 3.3 to fix warnings and
crashes of L1 guests. svn path=/dists/trunk/linux-2.6/; revision=18603
This commit is contained in:
Aurelien Jarno
parent
d5302538cf
commit
943fad2464
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@ -14,6 +14,10 @@ linux-2.6 (3.2.1-2) UNRELEASED; urgency=low
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* Build linux-libc-dev without multiarch if dpkg does not support it,
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to support backports
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[ Aurelien Jarno ]
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* [x86] Backport KVM nested VMX fixes from 3.3 to fix warnings and
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crashes of L1 guests.
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-- Ben Hutchings <ben@decadent.org.uk> Thu, 19 Jan 2012 05:42:57 +0000
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linux-2.6 (3.2.1-1) unstable; urgency=low
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@ -0,0 +1,111 @@
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From: Nadav Har'El <nyh@il.ibm.com>
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Date: Thu, 22 Sep 2011 13:52:56 +0300
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Subject: [PATCH 1/2] KVM: nVMX: Add KVM_REQ_IMMEDIATE_EXIT
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commit d6185f20a0efbf175e12831d0de330e4f21725aa upstream.
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This patch adds a new vcpu->requests bit, KVM_REQ_IMMEDIATE_EXIT.
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This bit requests that when next entering the guest, we should run it only
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for as little as possible, and exit again.
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We use this new option in nested VMX: When L1 launches L2, but L0 wishes L1
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to continue running so it can inject an event to it, we unfortunately cannot
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just pretend to have run L2 for a little while - We must really launch L2,
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otherwise certain one-off vmcs12 parameters (namely, L1 injection into L2)
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will be lost. So the existing code runs L2 in this case.
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But L2 could potentially run for a long time until it exits, and the
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injection into L1 will be delayed. The new KVM_REQ_IMMEDIATE_EXIT allows us
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to request that L2 will be entered, as necessary, but will exit as soon as
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possible after entry.
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Our implementation of this request uses smp_send_reschedule() to send a
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self-IPI, with interrupts disabled. The interrupts remain disabled until the
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guest is entered, and then, after the entry is complete (often including
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processing an injection and jumping to the relevant handler), the physical
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interrupt is noticed and causes an exit.
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On recent Intel processors, we could have achieved the same goal by using
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MTF instead of a self-IPI. Another technique worth considering in the future
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is to use VM_EXIT_ACK_INTR_ON_EXIT and a highest-priority vector IPI - to
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slightly improve performance by avoiding the useless interrupt handler
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which ends up being called when smp_send_reschedule() is used.
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Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
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Signed-off-by: Avi Kivity <avi@redhat.com>
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---
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arch/x86/kvm/vmx.c | 11 +++++++----
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arch/x86/kvm/x86.c | 7 ++++++-
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include/linux/kvm_host.h | 1 +
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3 files changed, 14 insertions(+), 5 deletions(-)
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diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
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index 579a0b5..d75d914 100644
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--- a/arch/x86/kvm/vmx.c
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+++ b/arch/x86/kvm/vmx.c
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@@ -3945,12 +3945,15 @@ static bool nested_exit_on_intr(struct kvm_vcpu *vcpu)
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static void enable_irq_window(struct kvm_vcpu *vcpu)
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{
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u32 cpu_based_vm_exec_control;
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- if (is_guest_mode(vcpu) && nested_exit_on_intr(vcpu))
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- /* We can get here when nested_run_pending caused
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- * vmx_interrupt_allowed() to return false. In this case, do
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- * nothing - the interrupt will be injected later.
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+ if (is_guest_mode(vcpu) && nested_exit_on_intr(vcpu)) {
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+ /*
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+ * We get here if vmx_interrupt_allowed() said we can't
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+ * inject to L1 now because L2 must run. Ask L2 to exit
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+ * right after entry, so we can inject to L1 more promptly.
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*/
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+ kvm_make_request(KVM_REQ_IMMEDIATE_EXIT, vcpu);
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return;
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+ }
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cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
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cpu_based_vm_exec_control |= CPU_BASED_VIRTUAL_INTR_PENDING;
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
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index 4c938da..e24edbc 100644
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--- a/arch/x86/kvm/x86.c
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+++ b/arch/x86/kvm/x86.c
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@@ -5648,6 +5648,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
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int r;
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bool req_int_win = !irqchip_in_kernel(vcpu->kvm) &&
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vcpu->run->request_interrupt_window;
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+ bool req_immediate_exit = 0;
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if (vcpu->requests) {
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if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
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@@ -5687,7 +5688,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
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record_steal_time(vcpu);
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if (kvm_check_request(KVM_REQ_NMI, vcpu))
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process_nmi(vcpu);
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-
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+ req_immediate_exit =
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+ kvm_check_request(KVM_REQ_IMMEDIATE_EXIT, vcpu);
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}
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r = kvm_mmu_reload(vcpu);
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@@ -5738,6 +5740,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
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srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
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+ if (req_immediate_exit)
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+ smp_send_reschedule(vcpu->cpu);
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+
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kvm_guest_enter();
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if (unlikely(vcpu->arch.switch_db_regs)) {
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diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
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index d526231..9fedeb3 100644
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--- a/include/linux/kvm_host.h
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+++ b/include/linux/kvm_host.h
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@@ -50,6 +50,7 @@
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#define KVM_REQ_APF_HALT 12
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#define KVM_REQ_STEAL_UPDATE 13
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#define KVM_REQ_NMI 14
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+#define KVM_REQ_IMMEDIATE_EXIT 15
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#define KVM_USERSPACE_IRQ_SOURCE_ID 0
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--
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1.7.8.3
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73
debian/patches/bugfix/x86/KVM-nVMX-Fix-warning-causing-idt-vectoring-info-beha.patch
vendored
Normal file
73
debian/patches/bugfix/x86/KVM-nVMX-Fix-warning-causing-idt-vectoring-info-beha.patch
vendored
Normal file
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@ -0,0 +1,73 @@
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From: Nadav Har'El <nyh@il.ibm.com>
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Date: Thu, 22 Sep 2011 13:53:26 +0300
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Subject: [PATCH 2/2] KVM: nVMX: Fix warning-causing idt-vectoring-info
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behavior
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commit 51cfe38ea50aa631f58ed8c340ed6f0143c325a8 upstream.
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When L0 wishes to inject an interrupt while L2 is running, it emulates an exit
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to L1 with EXIT_REASON_EXTERNAL_INTERRUPT. This was explained in the original
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nVMX patch 23, titled "Correct handling of interrupt injection".
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Unfortunately, it is possible (though rare) that at this point there is valid
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idt_vectoring_info in vmcs02. For example, L1 injected some interrupt to L2,
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and when L2 tried to run this interrupt's handler, it got a page fault - so
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it returns the original interrupt vector in idt_vectoring_info. The problem
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is that if this is the case, we cannot exit to L1 with EXTERNAL_INTERRUPT
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like we wished to, because the VMX spec guarantees that idt_vectoring_info
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and exit_reason_external_interrupt can never happen together. This is not
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just specified in the spec - a KVM L1 actually prints a kernel warning
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"unexpected, valid vectoring info" if we violate this guarantee, and some
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users noticed these warnings in L1's logs.
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In order to better emulate a processor, which would never return the external
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interrupt and the idt-vectoring-info together, we need to separate the two
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injection steps: First, complete L1's injection into L2 (i.e., enter L2,
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injecting to it the idt-vectoring-info); Second, after entry into L2 succeeds
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and it exits back to L0, exit to L1 with the EXIT_REASON_EXTERNAL_INTERRUPT.
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Most of this is already in the code - the only change we need is to remain
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in L2 (and not exit to L1) in this case.
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Note that the previous patch ensures (by using KVM_REQ_IMMEDIATE_EXIT) that
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although we do enter L2 first, it will exit immediately after processing its
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injection, allowing us to promptly inject to L1.
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Note how we test vmcs12->idt_vectoring_info_field; This isn't really the
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vmcs12 value (we haven't exited to L1 yet, so vmcs12 hasn't been updated),
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but rather the place we save, at the end of vmx_vcpu_run, the vmcs02 value
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of this field. This was explained in patch 25 ("Correct handling of idt
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vectoring info") of the original nVMX patch series.
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Thanks to Dave Allan and to Federico Simoncelli for reporting this bug,
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to Abel Gordon for helping me figure out the solution, and to Avi Kivity
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for helping to improve it.
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Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
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Signed-off-by: Avi Kivity <avi@redhat.com>
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---
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arch/x86/kvm/vmx.c | 7 ++++---
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1 files changed, 4 insertions(+), 3 deletions(-)
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diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
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index d75d914..6e28d58 100644
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--- a/arch/x86/kvm/vmx.c
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+++ b/arch/x86/kvm/vmx.c
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@@ -4080,11 +4080,12 @@ static void vmx_set_nmi_mask(struct kvm_vcpu *vcpu, bool masked)
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static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
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{
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if (is_guest_mode(vcpu) && nested_exit_on_intr(vcpu)) {
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- struct vmcs12 *vmcs12;
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- if (to_vmx(vcpu)->nested.nested_run_pending)
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+ struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
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+ if (to_vmx(vcpu)->nested.nested_run_pending ||
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+ (vmcs12->idt_vectoring_info_field &
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+ VECTORING_INFO_VALID_MASK))
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return 0;
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nested_vmx_vmexit(vcpu);
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- vmcs12 = get_vmcs12(vcpu);
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vmcs12->vm_exit_reason = EXIT_REASON_EXTERNAL_INTERRUPT;
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vmcs12->vm_exit_intr_info = 0;
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/* fall through to normal code, but now in L1, not L2 */
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--
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1.7.8.3
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@ -0,0 +1,2 @@
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+ bugfix/x86/KVM-nVMX-Add-KVM_REQ_IMMEDIATE_EXIT.patch
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+ bugfix/x86/KVM-nVMX-Fix-warning-causing-idt-vectoring-info-beha.patch
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