On Sat, Jun 08, 2013 at 11:15:37AM +0800, Xiao Guangrong wrote:
> From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
>
> Currently, memory synchronization is missed in emulator_fix_hypercall,
> please see the commit 758ccc89b83
> (KVM: x86: drop calling kvm_mmu_zap_all in emulator_fix_hypercall)
>
> This patch fixes it by introducing kvm_vcpus_hang_on_page_start() and
> kvm_vcpus_hang_on_page_end which unmap the patched page from guest
> and use kvm_flush_remote_tlbs() as the serializing instruction to
> ensure the memory coherence
> [ The SDM said that INVEPT, INVVPID and MOV (to control register, with
> the exception of MOV CR8) are the serializing instructions. ]
>
> The mmu-lock is held during host patches the page so that it stops vcpus
> to fix its further page fault
>
I have a patch to implement is much simple and in generic way, not
relying on MMU internals.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6402951..49774ab 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5517,7 +5517,7 @@ out:
}
EXPORT_SYMBOL_GPL(kvm_emulate_hypercall);
-static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
+static int emulator_fix_hypercall_cb(void *ctxt)
{
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
char instruction[3];
@@ -5528,6 +5528,14 @@ static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
return emulator_write_emulated(ctxt, rip, instruction, 3, NULL);
}
+static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
+{
+ struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
+ return kvm_exec_with_stopped_vcpu(vcpu->kvm,
+ emulator_fix_hypercall_cb, ctxt);
+}
+
+
/*
* Check if userspace requested an interrupt window, and that the
* interrupt window is open.
@@ -5761,6 +5769,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
kvm_deliver_pmi(vcpu);
if (kvm_check_request(KVM_REQ_SCAN_IOAPIC, vcpu))
vcpu_scan_ioapic(vcpu);
+ if (kvm_check_request(KVM_REQ_STOP_VCPU, vcpu)){
+ mutex_lock(&vcpu->kvm->lock);
+ mutex_unlock(&vcpu->kvm->lock);
+ }
}
if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e3aae6d..6c9361a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -125,6 +125,7 @@ static inline bool is_error_page(struct page *page)
#define KVM_REQ_EPR_EXIT 20
#define KVM_REQ_SCAN_IOAPIC 21
#define KVM_REQ_GLOBAL_CLOCK_UPDATE 22
+#define KVM_REQ_STOP_VCPU 23
#define KVM_USERSPACE_IRQ_SOURCE_ID 0
#define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1
@@ -576,6 +577,7 @@ void kvm_flush_remote_tlbs(struct kvm *kvm);
void kvm_reload_remote_mmus(struct kvm *kvm);
void kvm_make_mclock_inprogress_request(struct kvm *kvm);
void kvm_make_scan_ioapic_request(struct kvm *kvm);
+int kvm_exec_with_stopped_vcpu(struct kvm *kvm, int (*cb)(void *), void *data);
long kvm_arch_dev_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1580dd4..531e765 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -222,6 +222,18 @@ void kvm_make_scan_ioapic_request(struct kvm *kvm)
make_all_cpus_request(kvm, KVM_REQ_SCAN_IOAPIC);
}
+int kvm_exec_with_stopped_vcpu(struct kvm *kvm, int (*cb)(void *), void *data)
+{
+ int r;
+
+ mutex_lock(&kvm->lock);
+ make_all_cpus_request(kvm, KVM_REQ_STOP_VCPU);
+ r = cb(data);
+ mutex_unlock(&kvm->lock);
+
+ return r;
+}
+
int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
{
struct page *page;
--
Gleb.
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