On 08/10/22 12:50 am, Sean Christopherson wrote:
On Fri, Oct 07, 2022, Sean Christopherson wrote:
On Thu, Sep 15, 2022, Shivam Kumar wrote:
Let's keep kvm_vcpu_check_dirty_quota(), IMO that's still the least awful name.
[*] https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_all_Yo-2B82LjHSOdyxKzT-40google.com&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=4hVFP4-J13xyn-OcN0apTCh8iKZRosf5OJTQePXBMB8&m=0-XNirx6DRihxIvWzzJHJnErbZelq39geArwcitkIRgMl23nTXBs57QP543DuFnw&s=7zXRbLuhXLpsET-zMv7muSajxOFUoktaL97P3huVuhA&e=
Actually, I take that back. The code snippet itself is also flawed. If userspace
increases the quota (or disables it entirely) between KVM snapshotting the quota
and making the request, then there's no need for KVM to exit to userspace.
So I think this can be:
static void kvm_vcpu_is_dirty_quota_exchausted(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_HAVE_KVM_DIRTY_QUOTA
u64 dirty_quota = READ_ONCE(vcpu->run->dirty_quota);
return dirty_quota && (vcpu->stat.generic.pages_dirtied >= dirty_quota);
#else
return false;
#endif
}
and the usage becomes:
if (kvm_vcpu_is_dirty_quota_exhausted(vcpu))
kvm_make_request(KVM_REQ_DIRTY_QUOTA_EXIT, vcpu);
More thoughts in the x86 patch.
Snapshotting is not a requirement for now anyway. We have plans to
lazily update the quota, i.e. only when it needs to do more dirtying.
This helps us prevent overthrottling of the VM due to skewed cases where
some vcpus are mostly reading and the others are mostly wirting.
So, this looks good from every angle. The name
kvm_vcpu_is_dirty_quota_exchausted, though verbose, looks good to me.
