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Re: [Qemu-ppc] [PATCH] spapr: Correct RAM size calculation for HPT resiz
Re: [Qemu-ppc] [PATCH] spapr: Correct RAM size calculation for HPT resizing
Wed, 11 Oct 2017 11:04:53 +1100
On Tue, Oct 10, 2017 at 05:21:53PM +0200, Laurent Vivier wrote:
> On 10/10/2017 16:44, Greg Kurz wrote:
> > On Wed, 11 Oct 2017 00:21:59 +1100
> > David Gibson <address@hidden> wrote:
> >> In order to prevent the guest from forcing the allocation of large amounts
> >> of qemu memory (or host kernel memory, in the case of KVM HV), we limit
> >> the size of Hashed Page Table (HPT) it is allowed to allocated, based on
> >> its RAM size.
> >> However, the current calculation is not correct: it only adds up the size
> >> of plugged memory, ignoring the base memory size. This patch corrects it.
> >> While we're there, use get_plugged_memory_size() instead of directly
> >> calling pc_existing_dimms_capacity(). The only difference is that it
> >> will abort on failure, which is right: a failure here indicates something
> >> wrong within qemu.
> >> Signed-off-by: David Gibson <address@hidden>
> >> ---
> >> hw/ppc/spapr_hcall.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> >> index 8d72bb7c1c..06af1b15c0 100644
> >> --- a/hw/ppc/spapr_hcall.c
> >> +++ b/hw/ppc/spapr_hcall.c
> >> @@ -494,7 +494,7 @@ static target_ulong h_resize_hpt_prepare(PowerPCCPU
> >> *cpu,
> >> return H_PARAMETER;
> >> }
> >> - current_ram_size = pc_existing_dimms_capacity(&error_fatal);
> >> + current_ram_size = ram_size + get_plugged_memory_size();
> > current_ram_size is initialized earlier in this function:
> > uint64_t current_ram_size = MACHINE(spapr)->ram_size;
> > which is is initialized to ram_size in vl.c. Why not doing:
> > current_ram_size += get_plugged_memory_size();
> > ?
> I agree, it seems like the original intend of the first patch...
Yes, I think so. However, splitting the calculation like that
demonstrably misread someone reading the code (i.e. me), so I'm going
to just ditch the initializerin the new spin.
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
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