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 > 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? -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
