> From: Akshay Karle [mailto:akshay.a.karle@xxxxxxxxx] > Subject: Re: [RFC 1/2] kvm: host-side changes for tmem on KVM > > >> @@ -669,7 +670,6 @@ static struct zv_hdr *zv_create(struct x > >> int chunks = (alloc_size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT; > >> int ret; > >> > >> - BUG_ON(!irqs_disabled()); > > > > Can you explain why? > > Zcache is by default used in the non-virtualized environment for page compression. Whenever > a page is to be evicted from the page cache the spin_lock_irq is held on the page mapping. > To ensure that this is done, the BUG_ON(!irqs_disabled()) was used. > But now the situation is different, we are using zcache functions for kvm VM's. > So if any page of the guest is to be evicted the irqs should be disabled in just that > guest and not the host, so we removed the BUG_ON(!irqs_disabled()); line. I think irqs may still need to be disabled (in your code by the caller) since the tmem code (in tmem.c) takes spinlocks with this assumption. I'm not sure since I don't know what can occur with scheduling a kvm guest during an interrupt... can a different vcpu of the same guest be scheduled on this same host pcpu? Dan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
