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Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v4)
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v4) |
Date: |
Thu, 7 Nov 2013 19:53:04 -0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Nov 07, 2013 at 04:24:59PM +0100, Igor Mammedov wrote:
> On Wed, 6 Nov 2013 19:31:19 -0200
> Marcelo Tosatti <address@hidden> wrote:
>
> >
> > v2: condition enablement of new mapping to new machine types (Paolo)
> > v3: fix changelog
> > v4: rebase
> >
> > -----
> >
> >
> > 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 <address@hidden>
> >
> >
> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > index 12c436e..d29196d 100644
> > --- a/hw/i386/pc.c
> > +++ b/hw/i386/pc.c
> > @@ -1156,7 +1156,7 @@ 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, *ram_above_4g_piecetwo;
> > FWCfgState *fw_cfg;
> >
> > linux_boot = (kernel_filename != NULL);
> > @@ -1177,10 +1177,45 @@ 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));
> > - 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.
> > + *
> > + */
> I did some corner cases testing and there is alias overlapping in case
> -m 4096 -mem-path /var/lib/hugetlbfs/global/pagesize-1GB
>
> 0000000100000000-000000011fffffff (prio 0, RW): alias ram-above-4g-piecetwo
> @pc.ram 00000000e0000000-00000000ffffffff
> 0000000100000000-0000000100000000 (prio 0, RW): alias ram-above-4g @pc.ram
> 0000000100000000-0000000100000000
>
> perhaps zero sized ram-above-4g shouldn't be created at all?
Right.
> in addition ram-above-4g-piecetwo starts at half page offset 00000000e0000000
> but guest sees it 4Gb offset,
> wouldn't it cause the same issue patch tries to solve but only for
> ram-above-4g-piecetwo tail sync host/guest offsets
> are not 1Gb aligned?
Piece 1 is aligned. Piece 2 maps from tail of RAM (gpa) to start of hole
(ramblock).
> there is more misalignment with:
> -m 4097 -mem-path /var/lib/hugetlbfs/global/pagesize-1GB
>
> 0000000100000000-00000001000fffff (prio 0, RW): alias ram-above-4g @pc.ram
> 0000000100000000-00000001000fffff
Piece 1 is aligned.
> 0000000100100000-00000001200fffff (prio 0, RW): alias ram-above-4g-piecetwo
> @pc.ram 00000000e0000000-00000000ffffffff
Piece 2 is not. Should allocate one extra MB of RAM to align that. I'll
resend, thanks.
> where ram-above-4g-piecetwo is aligned with 1Gb+1Mb GPA offset, in addition
> to 500Mb offset of HPA.
> which would cause the same issue as above prehaps?
- Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v3), (continued)
[Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v4), Marcelo Tosatti, 2013/11/06
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 <=
[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 availableRe: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v6), Marcelo Tosatti, 2013/11/13
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