> -----Original Message----- > From: Alex Williamson <alex.williamson@xxxxxxxxxx> > Sent: 01 June 2021 15:14 > To: Thanos Makatos <thanos.makatos@xxxxxxxxxxx> > Cc: vfio-users@xxxxxxxxxx; John Levon <john.levon@xxxxxxxxxxx>; Swapnil > Ingle <swapnil.ingle@xxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx > Subject: Re: semantics of VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP > > On Tue, 1 Jun 2021 13:48:22 +0000 > Thanos Makatos <thanos.makatos@xxxxxxxxxxx> wrote: > > > (sending here as I can't find a relevant list in > > https://urldefense.proofpoint.com/v2/url?u=http-3A__vger.kernel.org_vg > > er- > 2Dlists.html&d=DwICAg&c=s883GpUCOChKOHiocYtGcg&r=XTpYsh5Ps2zJvtw > 6og > > > tti46atk736SI4vgsJiUKIyDE&m=E6G0G_Z_M2cIQvruwQk6NRrha3NkW8gdO11 > pPUm8vg > > k&s=-7KcTuEYFphAcU1aya0t_Jh4aP9jVPq2N2YxVu9Lu84&e= ) > > $ ./scripts/get_maintainer.pl include/uapi/linux/vfio.h Alex Williamson > <alex.williamson@xxxxxxxxxx> (maintainer:VFIO DRIVER) Cornelia Huck > <cohuck@xxxxxxxxxx> (reviewer:VFIO DRIVER) kvm@xxxxxxxxxxxxxxx (open > list:VFIO DRIVER) linux-kernel@xxxxxxxxxxxxxxx (open list) > > > I'm trying to understand the semantics of > > VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP. My (very rough) > understanding > > so far is that once a page gets pinned then it's considered dirty and > > if the page is still pinned then it remains dirty even after we're > > done serving VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP. Is my > > understanding correct? > > This is the current type1 implementation, but the semantics only require that > a page is reported dirty if it's actually been written. > Without support for tracking DMA writes, we assume that any page > accessible to the device is constantly dirty. This will be refined over time as > software and hardware support improves, but we currently error on the side > of assuming all pinned pages are always dirty. > Thanks, Makes sense, thanks. > > Alex
