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Re: [Qemu-ppc] [PATCH] spapr: Correct RAM size calculation for HPT resiz
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-ppc] [PATCH] spapr: Correct RAM size calculation for HPT resizing |
Date: |
Tue, 10 Oct 2017 17:21:53 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 |
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...
Thanks,
Laurent