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When a CPU is running a process, the ASID for that process is
held in a per-CPU variable (the "active ASIDs" array). When
the ASID allocator handles a rollover, it copies the active
ASIDs into a "reserved ASIDs" array to ensure that a process
currently running on another CPU will continue to run unaffected.
The active array is zero-ed to indicate that a rollover occurred.
Because of this mechanism, a reserved ASID is only remembered for
a single rollover. A subsequent rollover will completely refill
the reserved ASIDs array.
In a severely oversubscribed environment where a CPU can be
prevented from running for extended periods of time (think virtual
machines), the above has a horrible side effect:
[P{a} denotes process P running with ASID a]
CPU-0 CPU-1
A{x} [active = <x 0>]
[suspended] runs B{y} [active = <x y>]
[rollover:
active = <0 0>
reserved = <x y>]
runs B{y} [active = <0 y>
reserved = <x y>]
[rollover:
active = <0 0>
reserved = <0 y>]
runs C{x} [active = <0 x>]
[resumes]
runs A{x}
At that stage, both A and C have the same ASID, with deadly
consequences.
The fix is to preserve reserved ASIDs across rollovers if
the CPU doesn't have an active ASID when the rollover occurs.
Cc: <stable@vger.kernel.org> # 3.9
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Catalin Carinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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| .. | ||
| boot | ||
| common | ||
| configs | ||
| crypto | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mach-at91 | ||
| mach-bcm | ||
| mach-bcm2835 | ||
| mach-clps711x | ||
| mach-cns3xxx | ||
| mach-davinci | ||
| mach-dove | ||
| mach-ebsa110 | ||
| mach-ep93xx | ||
| mach-exynos | ||
| mach-footbridge | ||
| mach-gemini | ||
| mach-highbank | ||
| mach-imx | ||
| mach-integrator | ||
| mach-iop13xx | ||
| mach-iop32x | ||
| mach-iop33x | ||
| mach-ixp4xx | ||
| mach-kirkwood | ||
| mach-ks8695 | ||
| mach-lpc32xx | ||
| mach-mmp | ||
| mach-msm | ||
| mach-mv78xx0 | ||
| mach-mvebu | ||
| mach-mxs | ||
| mach-netx | ||
| mach-nomadik | ||
| mach-omap1 | ||
| mach-omap2 | ||
| mach-orion5x | ||
| mach-picoxcell | ||
| mach-prima2 | ||
| mach-pxa | ||
| mach-realview | ||
| mach-rpc | ||
| mach-s3c24xx | ||
| mach-s3c64xx | ||
| mach-s5p64x0 | ||
| mach-s5pc100 | ||
| mach-s5pv210 | ||
| mach-sa1100 | ||
| mach-shark | ||
| mach-shmobile | ||
| mach-socfpga | ||
| mach-spear | ||
| mach-sunxi | ||
| mach-tegra | ||
| mach-u300 | ||
| mach-ux500 | ||
| mach-versatile | ||
| mach-vexpress | ||
| mach-virt | ||
| mach-vt8500 | ||
| mach-w90x900 | ||
| mach-zynq | ||
| mm | ||
| net | ||
| nwfpe | ||
| oprofile | ||
| plat-iop | ||
| plat-omap | ||
| plat-orion | ||
| plat-pxa | ||
| plat-samsung | ||
| plat-versatile | ||
| tools | ||
| vfp | ||
| xen | ||
| Kconfig | ||
| Kconfig-nommu | ||
| Kconfig.debug | ||
| Makefile | ||