On 01/08/2015 02:45 AM, Christoffer Dall wrote: > On Wed, Jan 07, 2015 at 05:43:18PM -0800, Mario Smarduch wrote: >> Hi Christoffer, >> before going through your comments, I discovered that >> in 3.18.0-rc2 - a generic __get_user_pages_fast() >> was implemented, now ARM picks this up. This causes >> gfn_to_pfn_prot() to return meaningful 'writable' >> value for a read fault, provided the region is writable. >> >> Prior to that the weak version returned 0 and 'writable' >> had no optimization effect to set pte/pmd - RW on >> a read fault. >> >> As a consequence dirty logging broke in 3.18, I was seeing Correction on this, proper __get_user_pages_fast() behavior exposed a bug in page logging code. >> weird but very intermittent issues. I just put in the >> additional few lines to fix it, prevent pte RW (only R) on >> read faults while logging writable region. >> >> On 01/07/2015 04:38 AM, Christoffer Dall wrote: >>> On Wed, Dec 17, 2014 at 06:07:29PM -0800, Mario Smarduch wrote: >>>> This patch is a followup to v15 patch series, with following changes: >>>> - When clearing/dissolving a huge, PMD mark huge page range dirty, since >>>> the state of whole range is unknown. After the huge page is dissolved >>>> dirty page logging is at page granularity. >>> >>> What is the sequence of events where you could have dirtied another page >>> within the PMD range after the user initially requested dirty page >>> logging? >> >> No there is none. My issue was the start point for tracking dirty pages >> and that would be second call to dirty log read. Not first >> call after initial write protect where any page in range can >> be assumed dirty. I'll remove this, not sure if there would be any >> use case to call dirty log only once. >> > > Calling dirty log once can not give you anything meaningful, right? You > must assume all memory is 'dirty' at this point, no? There is the interval between KVM_MEM_LOG_DIRTY_PAGES and first call to KVM_GET_DIRTY_LOG. Not sure of any use case, maybe enable logging, wait a while do a dirty log read, disable logging. Get an accumulated snapshot of dirty page activity. - Mario > > -Christoffer > -- 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
