Will Deacon 195bbcac2e ARM: 7500/1: io: avoid writeback addressing modes for __raw_ accessors ... Data aborts taken to hyp mode do not provide a valid instruction syndrome field in the HSR if the faulting instruction is a memory access using a writeback addressing mode. For hypervisors emulating MMIO accesses to virtual peripherals, taking such an exception requires disassembling the faulting instruction in order to determine the behaviour of the access. Since this requires manually walking the two stages of translation, the world must be stopped to prevent races against page aging in the guest, where the first-stage translation is invalidated after the hypervisor has translated to an IPA and the physical page is reused for something else. This patch avoids taking this heavy performance penalty when running Linux as a guest by ensuring that our I/O accessors do not make use of writeback addressing modes. Cc: Marc Zyngier <marc.zyngier@arm.com> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>		2012-08-25 09:22:32 +01:00
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asm	ARM: 7500/1: io: avoid writeback addressing modes for __raw_ accessors	2012-08-25 09:22:32 +01:00