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SubjectRe: [PATCH RESEND] kvm:x86:Fix error handling in the function kvm_lapic_sync_to_vapic
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On 10/01/2016 06:28, Nicholas Krause wrote:
> This fixes error handling in the function kvm_lapic_sync_to_vapic
> to check the value of the call to kvm_write_guest_cached to see if
> it failed by returning a error code and if so execute WARN_ON to
> allow the user to see in their logs the failure when executing the
> function kvm_lapic_sync_to_vapic.
>
> Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
> ---
> arch/x86/kvm/lapic.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 2a5ca97..f3946c0 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1935,7 +1935,7 @@ static void apic_sync_pv_eoi_to_guest(struct kvm_vcpu *vcpu,
> void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu)
> {
> u32 data, tpr;
> - int max_irr, max_isr;
> + int max_irr, max_isr, ret;
> struct kvm_lapic *apic = vcpu->arch.apic;
>
> apic_sync_pv_eoi_to_guest(vcpu, apic);
> @@ -1952,8 +1952,9 @@ void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu)
> max_isr = 0;
> data = (tpr & 0xff) | ((max_isr & 0xf0) << 8) | (max_irr << 24);
>
> - kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.apic->vapic_cache, &data,
> - sizeof(u32));
> + ret = kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.apic->vapic_cache, &data,
> + sizeof(u32));
> + WARN_ON(ret);
> }
>
> int kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr)
>

Again... no. The error can be triggered by the guest. Incorrect
behavior of the guest should *never* result in a WARN in the host.

Paolo

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