On 05/21/2012 02:17 PM, Hao, Xudong wrote: > > -----Original Message----- > > From: Avi Kivity [mailto:avi@xxxxxxxxxx] > > Sent: Monday, May 21, 2012 6:48 PM > > To: Hao, Xudong > > Cc: Marcelo Tosatti; Xudong Hao; kvm@xxxxxxxxxxxxxxx; > > linux-kernel@xxxxxxxxxxxxxxx; Shan, Haitao; Zhang, Xiantao > > Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping > > > > On 05/21/2012 01:35 PM, Hao, Xudong wrote: > > > > > > > > That doesn't answer the question. An atomic operation is now > > non-atomic. > > > > > > > > You can calculate shadow_accessed_bit and keep on using clear_bit(), or > > > > switch to cmpxchg64(), but don't just drop the dirty bit here. > > > > > > > > > > I know your meaning. How about this changes: > > > > > > ... > > > young = 1; > > > + if (enable_ept_ad_bits) > > > + clear_bit(ffs(shadow_accessed_mask), (unsigned long > > *)spte); > > > > ffs() returns an off-by-one result, so this needs to be adjusted. > > Yes, it need to decrease 1, I'll send v3 version for patch4, any other comments? I think it's fine. > > IIRC > > bsfl is slow, but this shouldn't be a problem here. > > > > I do not know the story... > No story, bsf is a relatively slow instruction, but it shouldn't affect us here; this isn't a fast path and in any case it's only a few cycles. -- error compiling committee.c: too many arguments to function -- 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
