Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v3)

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 5 Nov 2013 23:55:43 -0200
Marcelo Tosatti <mtosatti@redhat.com> wrote:

> 
> 
> v2: condition enablement of new mapping to new machine types (Paolo)
> v3: fix changelog
> 
> -----
> 
> 
> Align guest physical address and host physical address
> beyond guest 4GB on a 1GB boundary.
> 
> Otherwise 1GB TLBs cannot be cached for the range.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 0c313fe..534e067 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1116,7 +1116,7 @@ FWCfgState *pc_memory_init(MemoryRegion *system_memory,
[...]
> +        /*
> +         *
> +         * 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) {
'gb_align' is one shot usage, it would be better to just add it as an argument
to pc_memory_init(). That would allow to avoid extending PcGuestInfo needlessly,
since gb_align isn't reused.

> +            unsigned long holesize = 0x100000000ULL - below_4g_mem_size;
> +
> +            memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> +                                    0x100000000ULL,
> +                                    above_4g_mem_size - holesize);
> +            memory_region_add_subregion(system_memory, 0x100000000ULL,
>                                      ram_above_4g);
[...]
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 6083839..00afe4a 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -20,6 +20,7 @@ typedef struct PcPciInfo {
>  struct PcGuestInfo {
>      bool has_pci_info;
>      bool isapc_ram_fw;
> +    bool gb_align;
>      FWCfgState *fw_cfg;
>  };
it doesn't apply anymore.