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Re: [Qemu-devel] [PATCH] extend limit of physical sections number
From: |
Amos Kong |
Subject: |
Re: [Qemu-devel] [PATCH] extend limit of physical sections number |
Date: |
Tue, 19 Nov 2013 19:11:07 +0800 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sat, Sep 28, 2013 at 12:49:20AM +0800, Amos Kong wrote:
> # qemu -drive file=/disk0,if=none,id=v0,format=qcow2 \
> -device virtio-blk-pci,drive=v0,id=v00,multifunction=on,addr=0x04.0
> ....
>
> Launching guest with more than 32 virtio-blk disks,
> qemu will crash, because there are too many BARs.
>
> This patch brings the limit of non-tcg up by a factor
> of 8 (32767 / 4096), i.e. 32*8 = 256.
I re-tested with latest guest kernel (3.10.0-rc5),
crash still occurred after applied this patch.
1. phys_section_add: assert(next_map.sections_nb < TARGET_PAGE_SIZE);
crash
2. phys_section_add: assert(next_map.sections_nb < SHRT_MAX);
crash
3. without this assert of next_map.sections_nb in phys_section_add
crash occurred at register_subpage():
assert(existing->mr->subpage || existing->mr == &io_mem_unassigned);
> Signed-off-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Amos Kong <address@hidden>
> ---
> exec.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index 5aef833..f639c01 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -763,11 +763,18 @@ void phys_mem_set_alloc(void *(*alloc)(ram_addr_t))
>
> static uint16_t phys_section_add(MemoryRegionSection *section)
> {
> - /* The physical section number is ORed with a page-aligned
> - * pointer to produce the iotlb entries. Thus it should
> - * never overflow into the page-aligned value.
> - */
> - assert(next_map.sections_nb < TARGET_PAGE_SIZE);
> + if (tcg_enabled()) {
> + /* The physical section number is ORed with a page-aligned
> + * pointer to produce the iotlb entries. Thus it should
> + * never overflow into the page-aligned value.
> + */
> + assert(next_map.sections_nb < TARGET_PAGE_SIZE);
> + } else {
> + /* For KVM or Xen we can use the full range of the ptr field
> + * in PhysPageEntry.
> + */
> + assert(next_map.sections_nb < SHRT_MAX);
> + }
>
> if (next_map.sections_nb == next_map.sections_nb_alloc) {
> next_map.sections_nb_alloc = MAX(next_map.sections_nb_alloc * 2,
> --
> 1.8.3.1
>
--
Amos.