mirror of
https://github.com/FEX-Emu/linux.git
synced 2024-12-29 04:45:05 +00:00
a987370f8e
We're using __get_free_pages with to allocate the guest's stage-2
PGD. The standard behaviour of this function is to return a set of
pages where only the head page has a valid refcount.
This behaviour gets us into trouble when we're trying to increment
the refcount on a non-head page:
page:ffff7c00cfb693c0 count:0 mapcount:0 mapping: (null) index:0x0
flags: 0x4000000000000000()
page dumped because: VM_BUG_ON_PAGE((*({ __attribute__((unused)) typeof((&page->_count)->counter) __var = ( typeof((&page->_count)->counter)) 0; (volatile typeof((&page->_count)->counter) *)&((&page->_count)->counter); })) <= 0)
BUG: failure at include/linux/mm.h:548/get_page()!
Kernel panic - not syncing: BUG!
CPU: 1 PID: 1695 Comm: kvm-vcpu-0 Not tainted 4.0.0-rc1+ #3825
Hardware name: APM X-Gene Mustang board (DT)
Call trace:
[<ffff80000008a09c>] dump_backtrace+0x0/0x13c
[<ffff80000008a1e8>] show_stack+0x10/0x1c
[<ffff800000691da8>] dump_stack+0x74/0x94
[<ffff800000690d78>] panic+0x100/0x240
[<ffff8000000a0bc4>] stage2_get_pmd+0x17c/0x2bc
[<ffff8000000a1dc4>] kvm_handle_guest_abort+0x4b4/0x6b0
[<ffff8000000a420c>] handle_exit+0x58/0x180
[<ffff80000009e7a4>] kvm_arch_vcpu_ioctl_run+0x114/0x45c
[<ffff800000099df4>] kvm_vcpu_ioctl+0x2e0/0x754
[<ffff8000001c0a18>] do_vfs_ioctl+0x424/0x5c8
[<ffff8000001c0bfc>] SyS_ioctl+0x40/0x78
CPU0: stopping
A possible approach for this is to split the compound page using
split_page() at allocation time, and change the teardown path to
free one page at a time. It turns out that alloc_pages_exact() and
free_pages_exact() does exactly that.
While we're at it, the PGD allocation code is reworked to reduce
duplication.
This has been tested on an X-Gene platform with a 4kB/48bit-VA host
kernel, and kvmtool hacked to place memory in the second page of
the hardware PGD (PUD for the host kernel). Also regression-tested
on a Cubietruck (Cortex-A7).
[ Reworked to use alloc_pages_exact() and free_pages_exact() and to
return pointers directly instead of by reference as arguments
- Christoffer ]
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
|
||
|---|---|---|
| .. | ||
| boot | ||
| common | ||
| configs | ||
| crypto | ||
| firmware | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mach-asm9260 | ||
| mach-at91 | ||
| mach-axxia | ||
| mach-bcm | ||
| mach-berlin | ||
| mach-clps711x | ||
| mach-cns3xxx | ||
| mach-davinci | ||
| mach-digicolor | ||
| mach-dove | ||
| mach-ebsa110 | ||
| mach-efm32 | ||
| mach-ep93xx | ||
| mach-exynos | ||
| mach-footbridge | ||
| mach-gemini | ||
| mach-highbank | ||
| mach-hisi | ||
| mach-imx | ||
| mach-integrator | ||
| mach-iop13xx | ||
| mach-iop32x | ||
| mach-iop33x | ||
| mach-ixp4xx | ||
| mach-keystone | ||
| mach-ks8695 | ||
| mach-lpc32xx | ||
| mach-mediatek | ||
| mach-meson | ||
| mach-mmp | ||
| mach-moxart | ||
| mach-msm | ||
| mach-mv78xx0 | ||
| mach-mvebu | ||
| mach-mxs | ||
| mach-netx | ||
| mach-nomadik | ||
| mach-nspire | ||
| mach-omap1 | ||
| mach-omap2 | ||
| mach-orion5x | ||
| mach-picoxcell | ||
| mach-prima2 | ||
| mach-pxa | ||
| mach-qcom | ||
| mach-realview | ||
| mach-rockchip | ||
| mach-rpc | ||
| mach-s3c24xx | ||
| mach-s3c64xx | ||
| mach-s5pv210 | ||
| mach-sa1100 | ||
| mach-shmobile | ||
| mach-socfpga | ||
| mach-spear | ||
| mach-sti | ||
| mach-sunxi | ||
| mach-tegra | ||
| mach-u300 | ||
| mach-ux500 | ||
| mach-versatile | ||
| mach-vexpress | ||
| mach-vt8500 | ||
| mach-w90x900 | ||
| mach-zynq | ||
| mm | ||
| net | ||
| nwfpe | ||
| oprofile | ||
| plat-iop | ||
| plat-omap | ||
| plat-orion | ||
| plat-pxa | ||
| plat-samsung | ||
| plat-versatile | ||
| probes | ||
| tools | ||
| vfp | ||
| xen | ||
| Kconfig | ||
| Kconfig-nommu | ||
| Kconfig.debug | ||
| Makefile | ||