Re: [PATCH 0/5] ARM virt: Add NVDIMM support

[Andrew Jones]

On Tue, Nov 26, 2019 at 09:56:55AM +0100, Igor Mammedov wrote:
> On Mon, 25 Nov 2019 16:25:54 +0000
> Shameerali Kolothum Thodi <address@hidden> wrote:
> > > -    Name (MEMA, 0xBFBFD000)
> > > +    Name (MEMA, 0xFFFF0000)
> > > 
> > > However value here is suspicious. If I recall right it should
> > > point to DMS buffer allocated by firmware somewhere in the guest RAM.  
> > 
> > But then it will be horribly wrong and will result in inconsistent behavior
> > as well, right?
> 
> I'd thinks so. I'm not sure what happens but RAM starts at 0x100000000
> which is above the address you have in MEMA so you shouldn't have
> sensible data there and access probably should raise some sort of error.
> 
> CCing Drew

RAM starts at 0x40000000 (the 1G boundary). So 0xffff0000 is OK, assuming
you want this just below the 3G boundary. With TCG, a data abort exception
will be injected for any access to an unmapped region. With KVM, unless
paging is enabled in the guest, then reads of unmapped regions will return
zero and writes will be ignored.

Thanks,
drew