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The PL031 RTC tracks the difference between the guest RTC and the host RTC using a tick_offset field. For migration, however, we currently always migrate the offset between the guest and the vm_clock, even if the RTC clock is not the same as the vm_clock; this was an attempt to retain migration backwards compatibility. Unfortunately this results in the RTC behaving oddly across a VM state save and restore -- since the VM clock stands still across save-then-restore, regardless of how much real world time has elapsed, the guest RTC ends up out of sync with the host RTC in the restored VM. Fix this by migrating the raw tick_offset. To retain migration compatibility as far as possible, we have a new property migrate-tick-offset; by default this is 'true' and we will migrate the true tick offset in a new subsection; if the incoming data has no subsection we fall back to the old vm_clock-based offset information, so old->new migration compatibility is preserved. For complete new->old migration compatibility, the property is set to 'false' for 4.0 and earlier machine types (this will only affect 'virt-4.0' and below, as none of the other pl031-using machines are versioned). Reported-by: Russell King <rmk@armlinux.org.uk> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Message-id: 20190709143912.28905-1-peter.maydell@linaro.org
47 lines
1.1 KiB
C
47 lines
1.1 KiB
C
/*
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* ARM AMBA PrimeCell PL031 RTC
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*
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* Copyright (c) 2007 CodeSourcery
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Contributions after 2012-01-13 are licensed under the terms of the
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* GNU GPL, version 2 or (at your option) any later version.
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*/
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#ifndef HW_TIMER_PL031_H
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#define HW_TIMER_PL031_H
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#include "hw/sysbus.h"
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#define TYPE_PL031 "pl031"
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#define PL031(obj) OBJECT_CHECK(PL031State, (obj), TYPE_PL031)
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typedef struct PL031State {
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SysBusDevice parent_obj;
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MemoryRegion iomem;
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QEMUTimer *timer;
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qemu_irq irq;
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/*
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* Needed to preserve the tick_count across migration, even if the
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* absolute value of the rtc_clock is different on the source and
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* destination.
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*/
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uint32_t tick_offset_vmstate;
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uint32_t tick_offset;
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bool tick_offset_migrated;
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bool migrate_tick_offset;
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uint32_t mr;
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uint32_t lr;
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uint32_t cr;
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uint32_t im;
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uint32_t is;
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} PL031State;
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#endif
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