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Date: Mon, 22 Oct 2012 14:58:23 +0200 From: Avi Kivity <avi@...hat.com> To: Jan Kiszka <jan.kiszka@...mens.com> CC: Gleb Natapov <gleb@...hat.com>, Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>, Marcelo Tosatti <mtosatti@...hat.com>, LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org> Subject: Re: [PATCH] KVM: x86: fix vcpu->mmio_fragments overflow On 10/22/2012 02:55 PM, Jan Kiszka wrote: >> Since the userspace change is needed the idea is dead, but if we could >> implement it I do not see how it can hurt the latency if it would be the >> only mechanism to use coalesced mmio buffer. Checking that the ring buffer >> is empty is cheap and if it is not empty it means that kernel just saved >> you a lot of 8 bytes exists so even after iterating over all the entries there >> you still saved a lot of time. > > When taking an exit for A, I'm not interesting in flushing stuff for B > unless I have a dependency. Thus, buffers would have to be per device > before extending their use. Any mmio exit has to flush everything. For example a DMA caused by an e1000 write has to see any writes to the framebuffer, in case the guest is transmitting its framebuffer to the outside world. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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