similar to: Migration b/w nodes with different security models

Move the PAGE_POISON value to page_poison.c and add a function to enable callers from a kernel module to get the poison value if the page poisoning feature is in use. This also avoids callers directly checking PAGE_POISON regardless of whether the feature is enabled. Signed-off-by: Wei Wang <wei.w.wang at intel.com> Cc: Andrew Morton <akpm at linux-foundation.org> Cc: Michal Hocko

On Tue, Apr 21, 2020 at 12:29 AM David Hildenbrand <david at redhat.com> wrote: > > >>> 2. Can we assume that the guest will always rewrite the page after the > >>> deflate in the case of init_on_free or poison? > >> > >> Depends on what we think is the right way to do - IOW if we think "some > >> other content" as mentioned

>>> What is the expectation there? I assume we are saying either >>> poison_val or unmodified? If so I would think the inflate case makes >>> much more sense as that is where the madvise is called that will >>> discard the data. If so it would be pretty easy to just add a check >>> for the poison value to the same spot we check >>>

On Mon, Apr 27, 2020 at 8:09 AM David Hildenbrand <david at redhat.com> wrote: > > On 27.04.20 16:58, Alexander Duyck wrote: > > On Mon, Apr 27, 2020 at 1:08 AM David Hildenbrand <david at redhat.com> wrote: > >> > >> On 24.04.20 18:24, Alexander Duyck wrote: > >>> From: Alexander Duyck <alexander.h.duyck at linux.intel.com> >

On Tue, Apr 21, 2020 at 8:18 AM David Hildenbrand <david at redhat.com> wrote: > > >> > >> That leaves us with either > >> > >> 1. "Pages hinted via VIRTIO_BALLOON_F_FREE_PAGE_HINT might get replaced > >> by zero page. However, as soon as the page is written by the guest (even > >> before the hinting request was processed by the

On Tue, Jan 27, 2015 at 7:23 PM, Sanjoy Das <sanjoy at playingwithpointers.com> wrote: > Hi David, > > I spent some time thinking about poison semantics this way, but here > is where I always get stuck: > > Consider the IR fragment > > %x = zext i32 %maybe_poison to i64 > %y = lshr i64 %x 32 > %ptr = gep %global, %y > store 42 to %ptr > > If

Hello, on libvirt 1.2.4 and two nodes with E5-2620 and E5-2650, I am not able to migrate vm with cpu=host-passthrough with error: internal error: can't get vmdef the only difference between sender and receiver` cpus is the frequency and identification string. Is this behaviour expected?

On Thu, Apr 16, 2020 at 04:52:42PM -0700, Alexander Duyck wrote: > On Thu, Apr 16, 2020 at 3:13 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > On Thu, Apr 16, 2020 at 12:30:38PM -0700, Alexander Duyck wrote: > > > From: Alexander Duyck <alexander.h.duyck at linux.intel.com> > > > > > > If we have free page hinting or page reporting

On Mon, Apr 20, 2020 at 6:28 AM David Hildenbrand <david at redhat.com> wrote: > > >>> Now we are talking about what's safe to do with the page. > >>> > >>> If POISON flag is set by hypervisor but clear by guest, > >>> or poison_val is 0, then it's clear it's safe to blow > >>> away the page if we can figure out

On 01/28/2015 07:02 AM, Sean Silva wrote: > Could you maybe provide an example where replacing `%always_poison` > with `undef` will change the meaning? At least for me, the thing that > I'm most unclear about is how poison differs from undef. I will second this request for much the same reason. > > -- Sean Silva > > On Wed, Jan 28, 2015 at 2:50 AM, David Majnemer >

On 12/01/2017 11:49 PM, Michael S. Tsirkin wrote: > On Wed, Nov 29, 2017 at 09:55:26PM +0800, Wei Wang wrote: >> The guest free pages should not be discarded by the live migration thread >> when page poisoning is enabled with PAGE_POISONING_NO_SANITY=n, because >> skipping the transfer of such poisoned free pages will trigger false >> positive when new pages are

On Fri, Apr 17, 2020 at 11:07:38AM +0200, David Hildenbrand wrote: > On 17.04.20 10:50, Michael S. Tsirkin wrote: > > On Fri, Apr 17, 2020 at 09:49:03AM +0200, David Hildenbrand wrote: > >> On 17.04.20 08:28, Michael S. Tsirkin wrote: > >>> On Thu, Apr 16, 2020 at 04:52:42PM -0700, Alexander Duyck wrote: > >>>> On Thu, Apr 16, 2020 at 3:13 PM Michael S.

> > // Members are initialized to poison at object creation. >> p = alloca {i8, i32} // p[0], p[4~7] are poison >> p[0] is an i8, so it shouldn't be poison? > > My interpretation of standard is that reading uninitialized char can also yield trap representation. If uninitialized, char variable has indeterminate value, and C/C++ does not seem to forbid reading trap

On Thu, Apr 16, 2020 at 3:13 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > On Thu, Apr 16, 2020 at 12:30:38PM -0700, Alexander Duyck wrote: > > From: Alexander Duyck <alexander.h.duyck at linux.intel.com> > > > > If we have free page hinting or page reporting enabled we should disable it > > if the pages are poisoned or initialized on free and we

On Tue, Feb 3, 2015 at 3:15 AM, Nuno Lopes <nuno.lopes at ist.utl.pt> wrote: > Hi, > > > > Thanks David for putting up this proposal together! > > I like the idea of having poison values behave more like undef (i.e., per > bit, with run-time behavior). > > One of the problems this proposal solves is speculation of 'a && b' into > 'a &

On Mon, Dec 11, 2017 at 02:38:45PM +0800, Wei Wang wrote: > On 12/01/2017 11:49 PM, Michael S. Tsirkin wrote: > > On Wed, Nov 29, 2017 at 09:55:26PM +0800, Wei Wang wrote: > > > The guest free pages should not be discarded by the live migration thread > > > when page poisoning is enabled with PAGE_POISONING_NO_SANITY=n, because > > > skipping the transfer of

On Mon, Dec 11, 2017 at 02:38:45PM +0800, Wei Wang wrote: > On 12/01/2017 11:49 PM, Michael S. Tsirkin wrote: > > On Wed, Nov 29, 2017 at 09:55:26PM +0800, Wei Wang wrote: > > > The guest free pages should not be discarded by the live migration thread > > > when page poisoning is enabled with PAGE_POISONING_NO_SANITY=n, because > > > skipping the transfer of

In the section about poison values, the LLVM language reference manual says: "Values other than phi nodes depend on their operands." This implies that a select instruction's output can be poisoned by its not-selected argument value. If select were poisoned only by its selected argument, we would expect this fact to be mentioned specifically, as it is for phi. Next I'll

On 27.04.20 16:58, Alexander Duyck wrote: > On Mon, Apr 27, 2020 at 1:08 AM David Hildenbrand <david at redhat.com> wrote: >> >> On 24.04.20 18:24, Alexander Duyck wrote: >>> From: Alexander Duyck <alexander.h.duyck at linux.intel.com> >>> >>> We should disable free page reporting if page poisoning is enabled in the >>> kernel but we

On Thu, Jan 31, 2013 at 12:11 AM, Marcelo Tosatti <mtosatti at redhat.com> wrote: > On Wed, Jan 30, 2013 at 11:21:08AM +0300, Andrey Korolyov wrote: >> On Wed, Jan 30, 2013 at 3:15 AM, Marcelo Tosatti <mtosatti at redhat.com> wrote: >> > On Tue, Jan 29, 2013 at 02:35:02AM +0300, Andrey Korolyov wrote: >> >> On Mon, Jan 28, 2013 at 5:56 PM, Andrey Korolyov