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Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6)
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6) |
Date: |
Wed, 13 Nov 2013 18:39:27 -0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Wed, Nov 13, 2013 at 05:58:32PM -0200, Marcelo Tosatti wrote:
> On Wed, Nov 13, 2013 at 06:13:15PM +0100, Paolo Bonzini wrote:
> > > assert(piecetwosize <= holesize);
> > >
> > > piecetwosize = MIN(above_4g_mem_size, piecetwosize);
> > > if ((above_4g_mem_size - piecetwosize) > 0) {
> > > 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);
> > > } else {
> > > g_free(ram_above_4g);
> > > }
> > > 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,
> > > ram_above_4g_piecetwo);
> >
> > There is still a small problem in that the 2MB rounding must not be
> > done for old machine types.
> >
> > I did a really careful review of the code and everything else looks okay
> > to me. However, it grew by accretion from v1 and now it took me really a
> > long time to figure it out... I adjusted it a bit and the result seems
> > easier to understand to me.
> >
> > Here's the hw/i386/pc.c part of the patch (the patch from v6 is unreadable):
> >
> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > index 12c436e..f2fd138 100644
> > --- a/hw/i386/pc.c
> > +++ b/hw/i386/pc.c
> > @@ -1156,8 +1156,10 @@ FWCfgState *pc_memory_init(MemoryRegion
> > *system_memory,
> > {
> > int linux_boot, i;
> > MemoryRegion *ram, *option_rom_mr;
> > - MemoryRegion *ram_below_4g, *ram_above_4g;
> > + MemoryRegion *ram_below_4g, *ram_above_4g_pieceone,
> > *ram_above_4g_piecetwo;
> > FWCfgState *fw_cfg;
> > + uint64_t holesize, pieceonesize, piecetwosize;
> > + uint64_t memsize, align_offset;
> >
> > linux_boot = (kernel_filename != NULL);
> >
> > @@ -1165,26 +1167,74 @@ FWCfgState *pc_memory_init(MemoryRegion
> > *system_memory,
> > * aliases to address portions of it, mostly for backwards
> > compatibility
> > * with older qemus that used qemu_ram_alloc().
> > */
> > + memsize = below_4g_mem_size + above_4g_mem_size;
> > + holesize = 0x100000000ULL - below_4g_mem_size;
> > +
> > + /* If 1GB hugepages are used to back guest RAM, we want the
> > + * physical address 4GB to map to 4GB in the RAM, so that
> > + * memory beyond 4GB is aligned on a 1GB boundary, at the
> > + * host physical address space. Thus, the ram block range
> > + * [holestart, 4GB] is mapped to the last holesize bytes of RAM:
> > + *
> > + * 0 h 4G memsize-holesize
> > + *
> > + * contiguous-ram-block [xxxxxx][yyy][zzzzz]
> > + * '-----------.
> > + * guest-addr-space [xxxxxx] [zzzzz][yyy]
> > + *
> > + * This is only done in new-enough machine types, and of course
> > + * it is only necessary if the [zzzzz] block exists at all.
> > + */
> > + if (guest_info->gb_align && above_4g_mem_size > holesize) {
> > + /* Round the allocation up to 2 MB to use more hugepages.
To align to 2MB boundary, the number of hugepages is the same.
> > + * Remove the slack from the [yyy] piece so that pieceonesize
> > + * (and thus the start of piecetwo) remains aligned.
> > + */
> > + align_offset = ROUND_UP(memsize, 1UL << 21) - memsize;
> > + piecetwosize = holesize - align_offset;
> > + } else {
> > + /* There's no "piece one", all memory above 4G starts
Piece two.
> > + * at below_4g_mem_size in the RAM block. Also no need
> > + * to align anything.
> > + */
> > + align_offset = 0;
> > + piecetwosize = above_4g_mem_size;
> > + }
> > +
> > ram = g_malloc(sizeof(*ram));
> > - memory_region_init_ram(ram, NULL, "pc.ram",
> > - below_4g_mem_size + above_4g_mem_size);
> > + memory_region_init_ram(ram, NULL, "pc.ram", memsize + align_offset);
> > vmstate_register_ram_global(ram);
> > *ram_memory = ram;
> > +
> > ram_below_4g = g_malloc(sizeof(*ram_below_4g));
> > memory_region_init_alias(ram_below_4g, NULL, "ram-below-4g", ram,
> > 0, below_4g_mem_size);
> > memory_region_add_subregion(system_memory, 0, ram_below_4g);
> > +
> > + pieceonesize = above_4g_mem_size - piecetwosize;
> > + if (pieceonesize) {
> > + ram_above_4g_pieceone = g_malloc(sizeof(*ram_above_4g_pieceone));
> > + memory_region_init_alias(ram_above_4g_pieceone, NULL,
> > + "ram-above-4g-pieceone", ram,
> > + 0x100000000ULL, pieceonesize);
> > + memory_region_add_subregion(system_memory, 0x100000000ULL,
> > + ram_above_4g_pieceone);
> > + }
>
> Can you change the name of aliases and subregions without breaking
> migration?
>
> Its much simpler, i'm fine with it.
Test with Q35?
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v4), (continued)
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v4), Igor Mammedov, 2013/11/07
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v4), Marcelo Tosatti, 2013/11/07
- [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v5), Marcelo Tosatti, 2013/11/10
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v5), Igor Mammedov, 2013/11/12
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v5), Marcelo Tosatti, 2013/11/12
- [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6), Marcelo Tosatti, 2013/11/12
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6), Igor Mammedov, 2013/11/13
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6), Paolo Bonzini, 2013/11/13
- Message not available
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6),
Marcelo Tosatti <=
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6), Paolo Bonzini, 2013/11/13
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6), Michael S. Tsirkin, 2013/11/13