Re: [Qemu-devel] [PATCH] kvm-all: PAGE_SIZE should be real host page size

[Andrew Jones <drjones@redhat.com>]

On Tue, Nov 10, 2015 at 04:41:16PM +0100, Paolo Bonzini wrote:
> 
> 
> On 10/11/2015 01:23, Andrew Jones wrote:
> > Just noticed this while grepping TARGET_PAGE_SIZE for an unrelated
> > reason. I didn't use qemu_real_host_page_size as kvm_set_phys_mem()
> > does, because we'd need to make sure page_size_init() has run first.
> > 
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > ---
> >  kvm-all.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kvm-all.c b/kvm-all.c
> > index 1bc12737723c3..de9ff5971fb3b 100644
> > --- a/kvm-all.c
> > +++ b/kvm-all.c
> > @@ -45,8 +45,10 @@
> >  #include <sys/eventfd.h>
> >  #endif
> >  
> > -/* KVM uses PAGE_SIZE in its definition of COALESCED_MMIO_MAX */
> > -#define PAGE_SIZE TARGET_PAGE_SIZE
> > +/* KVM uses PAGE_SIZE in its definition of KVM_COALESCED_MMIO_MAX. We
> > + * need to use the real host PAGE_SIZE, as that's what KVM will use.
> > + */
> > +#define PAGE_SIZE getpagesize()
> >  
> >  //#define DEBUG_KVM
> >  
> > 
> 
> Is this a bugfix or just a cleanup?  If the former, on which targets?

It's a bugfix for any targets that have a TARGET_PAGE_SIZE !=
real-host-page-size. For example ARM has TARGET_PAGE_SIZE set to 1024,
even when the host is using 4k or 64k pages. However, I didn't find this
due to a bug, because on ARM I'm not using emulated devices that make
use of the coalesced-mmio feature at this time.

Thanks,
drew

> 
> Paolo
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