Re: [PATCH 8/9] Add VMEXIT handler and intercepts v2

[Alexander Graf]

On Sep 10, 2008, at 9:12 PM, Joerg Roedel wrote:
On Fri, Sep 05, 2008 at 09:51:23AM +0200, Alexander Graf wrote:
This adds the #VMEXIT intercept, so we return to the level 1 guest
when something happens in the level 2 guest that should return to
the level 1 guest.

v2 implements HIF handling and cleans up exception interception

Signed-off-by: Alexander Graf <[EMAIL PROTECTED]>
---
arch/x86/kvm/svm.c |  319 ++++++++++++++++++++++++++++++++++++++++++ 
++++++++++
1 files changed, 319 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index c47f039..8318a63 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -74,6 +74,13 @@ module_param(npt, int, S_IRUGO);
static void kvm_reput_irq(struct vcpu_svm *svm);
static void svm_flush_tlb(struct kvm_vcpu *vcpu);

+static int nested_svm_exit_handled(struct vcpu_svm *svm, bool  
kvm_override);
+static int nested_svm_vmexit(struct vcpu_svm *svm);
+static int nested_svm_vmsave(struct vcpu_svm *svm, void  
*nested_vmcb,
+                            void *arg2, void *opaque);
+static int nested_svm_check_exception(struct vcpu_svm *svm,  
unsigned nr,
+                                     bool has_error_code, u32 error_code);
+
static inline struct vcpu_svm *to_svm(struct kvm_vcpu *vcpu)
{
        return container_of(vcpu, struct vcpu_svm, vcpu);
@@ -223,6 +230,11 @@ static void svm_queue_exception(struct  
kvm_vcpu *vcpu, unsigned nr,
{
        struct vcpu_svm *svm = to_svm(vcpu);

+       /* If we are within a nested VM we'd better #VMEXIT and let the
+          guest handle the exception */
+	if (nested_svm_check_exception(svm, nr, has_error_code,  
error_code))
+               return;
+
        svm->vmcb->control.event_inj = nr
                | SVM_EVTINJ_VALID
                | (has_error_code ? SVM_EVTINJ_VALID_ERR : 0)
@@ -1185,6 +1197,43 @@ static int vmmcall_interception(struct  
vcpu_svm *svm, struct kvm_run *kvm_run)
        return 1;
}

+static int nested_svm_check_exception(struct vcpu_svm *svm,  
unsigned nr,
+                                     bool has_error_code, u32 error_code)
+{
+       if (is_nested(svm)) {
+               svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + nr;
+               svm->vmcb->control.exit_code_hi = 0;
+               svm->vmcb->control.exit_info_1 = error_code;
+               svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
+               if (nested_svm_exit_handled(svm, false)) {
+                       nsvm_printk("VMexit -> EXCP 0x%x\n", nr);
+
+                       nested_svm_vmexit(svm);
+                       return 1;
+               }
+       }
+
+       return 0;
+}
+
+static inline int nested_svm_intr(struct vcpu_svm *svm)
+{
+       if (is_nested(svm)) {
+               if (!(svm->vcpu.arch.hflags & HF_HIF_MASK))

HF_HIF_MASK?
Do you really need to check GIF if the vcpu is in guest mode? The  
guest
itself can't influence the GIF so it should always be set.

HIF is not GIF ;-). The HIF is the hidden interrupt flag, aka the IF  
flag the host had when it started VMRUN.



+                       return 0;
+
+               svm->vmcb->control.exit_code = SVM_EXIT_INTR;
+
+               if (nested_svm_exit_handled(svm, false)) {
+                       nsvm_printk("VMexit -> INTR\n");
+                       nested_svm_vmexit(svm);
+                       return 1;
+               }

The VMEXIT is only required if the guest vmcb has set V_INTR_MASKING.
Otherwise we can inject the interrupt directly into the l2 guest. This
is no problem for running KVM-in-KVM because KVM always sets
V_INTR_MASKING. But to keep the implementation close to real hardware
behavior this bit should be checked.

Right now I always force V_INTR_MASK to on in VMRUN, so we don't have  
to look at that case. It might be a good idea to simply implement the  
behavior though ...

[snip]

Alex
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