RE: [Qemu-devel] [PATCH 4/7] kvm: Add sanity checks to slot management

[Liu Yu-B13201]

> -----Original Message-----
> From: Jan Kiszka [mailto:address@hidden 
> Sent: Thursday, April 30, 2009 1:31 AM
> To: Hollis Blanchard
> Cc: Liu Yu-B13201; address@hidden; address@hidden
> Subject: Re: [Qemu-devel] [PATCH 4/7] kvm: Add sanity checks 
> to slot management
> 
> Hollis Blanchard wrote:
> > On Wed, 2009-04-29 at 12:38 +0200, Jan Kiszka wrote:
> >> Liu Yu-B13201 wrote:
> >>>> -----Original Message-----
> >>>> From: address@hidden 
> >>>> [mailto:address@hidden 
> >>>> On Behalf Of Jan Kiszka
> >>>> Sent: Sunday, April 12, 2009 1:20 AM
> >>>> To: address@hidden
> >>>> Subject: [Qemu-devel] [PATCH 4/7] kvm: Add sanity checks to 
> >>>> slot management
> >>>>
> >>>> Fail loudly if we run out of memory slot.
> >>>>
> >>>> Make sure that dirty log start/stop works with consistent 
> >>>> memory regions
> >>>> by reporting invalid parameters. This reveals several 
> >>>> inconsistencies in
> >>>> the vga code, patch to fix them follows later in this series.
> >>>>
> >>>> And, for simplicity reasons, also catch and report 
> unaligned memory
> >>>> regions passed to kvm_set_phys_mem (KVM works on page basis).
> >>>>
> >>> Commit d3f8d37fe2d0c24ec8bac9c94d5b0e2dc09c0d2a hurts kvm/powerpc
> >>> The alignment check in kvm_set_phys_mem prevents pci 
> controller and mpic initializing mmio regions.
> >> What is the alignment of those regions then? None? And do 
> regions of
> >> different types overlap even on the same page? Maybe the 
> check reveals
> >> some deeper conflict /wrt KVM. Can you point me to the 
> involved code files?
> > 
> > These PCI controllers make separate calls to
> > cpu_register_physical_memory() for separate callbacks. Reading
> > ppce500_pci_init(), for example:
> > 0xe0008000 -> CFGADDR (4 bytes)
> > 0xe0008004 -> CFGDATA (4 bytes)
> > 0xe0008c00 -> other registers
> > 
> > The loop in cpu_register_physical_memory_offset() handles "subpage"
> > registration. However, kvm_set_phys_mem() is called outside 
> that loop,
> > so it gets the non-page-aligned addresses.
> > 
> 
> Half-blind shot:
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index 32cd636..c2c760e 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -583,6 +583,9 @@ void kvm_set_phys_mem(target_phys_addr_t 
> start_addr,
>      int err;
> 
>      if (start_addr & ~TARGET_PAGE_MASK) {
> +        if (flags >= IO_MEM_UNASSIGNED) {
> +            return;
> +        }
>          fprintf(stderr, "Only page-aligned memory slots 
> supported\n");
>          abort();
>      }
> 
> If it works, it likely needs a cleaner approach to handle all cases.
> 

It works for me.