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Re: [Xen-devel] [PATCH] Add memory hotadd to pvops dom0

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Add memory hotadd to pvops dom0
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Sat, 19 Dec 2009 22:40:51 -0800
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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On 12/19/2009 06:47 AM, Jiang, Yunhong wrote:
+#define XENPF_mem_hotadd    59
+struct xenpf_mem_hotadd {
+       uint64_t spfn;
+       uint64_t epfn;
+       uint32_t pxm;
+       uint32_t flags;
  struct xen_platform_op {
        uint32_t cmd;
        uint32_t interface_version; /* XENPF_INTERFACE_VERSION */
@@ -362,6 +371,7 @@ struct xen_platform_op {
                struct xenpf_pcpuinfo          pcpu_info;
                struct xenpf_cpu_ol            cpu_ol;
                struct xenpf_cpu_hotadd        cpu_add;
+               struct xenpf_mem_hotadd        mem_add;
                uint8_t                        pad[128];
Should the size of the pad be decreased?
This is defined by xen hypervisor, and is intended for extenstion in future, I 

But Konrad's point is that if you have padding to reserve space for future expansion, shouldn't you decrease the padding when you actually increase the structure? Otherwise, if you can arbitrarily grow the structure, why do you need padding?


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