From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Chen, Tiejun" <tiejun.chen@intel.com>
Subject: Re: [RFC][PATCH 10/13] tools: extend
	XENMEM_set_memory_map
Date: Fri, 15 May 2015 10:57:15 +0800
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To: Jan Beulich <JBeulich@suse.com>, wei.liu2@citrix.com
Cc: tim@xen.org, kevin.tian@intel.com, ian.campbell@citrix.com, andrew.cooper3@citrix.com, Ian.Jackson@eu.citrix.com, xen-devel@lists.xen.org, stefano.stabellini@citrix.com, yang.z.zhang@intel.com
List-Id: xen-devel@lists.xenproject.org

On 2015/4/20 21:51, Jan Beulich wrote:
>>>> On 10.04.15 at 11:22, <tiejun.chen@intel.com> wrote:
>> --- a/tools/libxl/libxl_dom.c
>> +++ b/tools/libxl/libxl_dom.c
>> @@ -787,6 +787,70 @@ out:
>>       return rc;
>>   }
>>
>> +static int libxl__domain_construct_memmap(libxl_ctx *ctx,
>> +                                          libxl_domain_config *d_config,
>> +                                          uint32_t domid,
>> +                                          struct xc_hvm_build_args *args,
>> +                                          int num_pcidevs,
>> +                                          libxl_device_pci *pcidevs)
>> +{
>> +    unsigned int nr = 0, i;
>> +    /* We always own at least one lowmem entry. */
>> +    unsigned int e820_entries = 1;
>> +    uint64_t highmem_end = 0, highmem_size = args->mem_size - args->lowmem_size;
>> +    struct e820entry *e820 = NULL;
>> +
>> +    /* Add all rdm entries. */
>> +    e820_entries += d_config->num_rdms;
>> +
>> +    /* If we should have a highmem range. */
>> +    if (highmem_size)
>> +    {
>> +        highmem_end = (1ull<<32) + highmem_size;
>> +        e820_entries++;
>> +    }
>> +
>> +    e820 = malloc(sizeof(struct e820entry) * e820_entries);
>> +    if (!e820) {
>> +        return -1;
>> +    }
>> +
>> +    /* Low memory */
>> +    e820[nr].addr = 0x100000;
>> +    e820[nr].size = args->lowmem_size - 0x100000;
>> +    e820[nr].type = E820_RAM;
>
> If you really mean it to be this lax (not covering the low 1Mb), then
> you need to explain why in a comment (and the consuming side
> should also have a similar explanation then).
>

Okay, here may need this,

/* 

  * Low RAM starts at least from 1M to make sure all standard regions 

  * of the PC memory map, like BIOS, VGA memory-mapped I/O and vgabios, 

  * have enough space.
  */
#define GUEST_LOW_MEM_START_DEFAULT 0x100000

On the consuming side, I should clarify that we always preserve 1M.

>> +    nr++;
>> +
>> +    /* RDM mapping */
>> +    for (i = 0; i < d_config->num_rdms; i++) {
>> +        /*
>> +         * We should drop this kind of rdm entry.
>> +         */
>> +        if (d_config->rdms[i].flag == LIBXL_RDM_RESERVE_FLAG_INVALID)
>> +            continue;
>> +
>> +        e820[nr].addr = d_config->rdms[i].start;
>> +        e820[nr].size = d_config->rdms[i].size;
>> +        e820[nr].type = E820_RESERVED;
>> +        nr++;
>> +    }
>
> Is this guaranteed not to produce overlapping entries?
>

Right, I would add this at the beginning,

     if (e820_entries >= E820MAX) {
         LOG(ERROR, "Ooops! Too many entries in the memory map!\n");
         return -1;
     }

Thanks
Tiejun