Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v5)

[Igor Mammedov]

On Sun, 10 Nov 2013 18:47:53 -0200
Marcelo Tosatti <address@hidden> wrote:

[...]

> @@ -1177,10 +1182,50 @@ FWCfgState *pc_memory_init(MemoryRegion 
> *system_memory,
>      e820_add_entry(0, below_4g_mem_size, E820_RAM);
>      if (above_4g_mem_size > 0) {
>          ram_above_4g = g_malloc(sizeof(*ram_above_4g));
it is a memory leak when "ram-above-4g" is not created

> -        memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> -                                 below_4g_mem_size, above_4g_mem_size);
> -        memory_region_add_subregion(system_memory, 0x100000000ULL,
> +        /*
> +         *
> +         * If 1GB hugepages are used to back guest RAM, map guest address
> +         * space in the range [ramsize,ramsize+holesize] to the ram block
> +         * range [holestart, 4GB]
> +         *
> +         *                      0      h     4G     
> [ramsize,ramsize+holesize]
> +         *
> +         * guest-addr-space     [      ]     [      ][xxx]
> +         *                                /----------/
> +         * contiguous-ram-block [      ][xxx][     ]
> +         *
> +         * So that memory beyond 4GB is aligned on a 1GB boundary,
> +         * at the host physical address space.
> +         *
> +         */
> +        if (guest_info->gb_align) {
> +            uint64_t holesize = 0x100000000ULL - below_4g_mem_size;
> +            uint64_t piecetwosize = holesize - align_offset;
> +
> +            assert(piecetwosize <= holesize);
> +
> +            if ((above_4g_mem_size - piecetwosize) > 0) {
here is integer overflow,
reproducable with:  -mem-path /var/lib/hugetlbfs/global/pagesize-1GB -m 3600


> +                memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g",
> +                                         ram, 0x100000000ULL,
> +                                         above_4g_mem_size - piecetwosize);
> +                memory_region_add_subregion(system_memory, 0x100000000ULL,
> +                                         ram_above_4g);
> +            }
> +
> +            ram_above_4g_piecetwo = g_malloc(sizeof(*ram_above_4g_piecetwo));
> +            memory_region_init_alias(ram_above_4g_piecetwo, NULL,
> +                                     "ram-above-4g-piecetwo", ram,
> +                                     0x100000000ULL - holesize, 
> piecetwosize);
> +            memory_region_add_subregion(system_memory,
> +                                        0x100000000ULL +
> +                                        above_4g_mem_size - piecetwosize,
is there a guaranty that "ram-above-4g-piecetwo" will be mapped immediately
after "ram-above-4g" without any gap?

if there is no then you might need to change how e820_add_entry() for high ram
is handled and possibly CMOS value as well. 

> +                                        ram_above_4g_piecetwo);
> +        } else {
> +            memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> +                                    below_4g_mem_size, above_4g_mem_size);
> +            memory_region_add_subregion(system_memory, 0x100000000ULL,
>                                      ram_above_4g);
> +        }
>          e820_add_entry(0x100000000ULL, above_4g_mem_size, E820_RAM);
>      }
[...]
-- 
Regards,
  Igor