forked from Minki/linux
2dd887e321
Use READ_ONCE through the code, rather than explicit barriers. Suggested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
89 lines
1.9 KiB
C
89 lines
1.9 KiB
C
/*
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* Xen stolen ticks accounting.
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*/
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#include <linux/kernel.h>
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#include <linux/kernel_stat.h>
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#include <linux/math64.h>
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#include <linux/gfp.h>
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#include <asm/xen/hypervisor.h>
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#include <asm/xen/hypercall.h>
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#include <xen/events.h>
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#include <xen/features.h>
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#include <xen/interface/xen.h>
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#include <xen/interface/vcpu.h>
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#include <xen/xen-ops.h>
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/* runstate info updated by Xen */
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static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
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/* return an consistent snapshot of 64-bit time/counter value */
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static u64 get64(const u64 *p)
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{
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u64 ret;
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if (BITS_PER_LONG < 64) {
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u32 *p32 = (u32 *)p;
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u32 h, l, h2;
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/*
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* Read high then low, and then make sure high is
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* still the same; this will only loop if low wraps
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* and carries into high.
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* XXX some clean way to make this endian-proof?
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*/
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do {
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h = READ_ONCE(p32[1]);
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l = READ_ONCE(p32[0]);
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h2 = READ_ONCE(p32[1]);
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} while(h2 != h);
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ret = (((u64)h) << 32) | l;
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} else
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ret = READ_ONCE(*p);
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return ret;
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}
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/*
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* Runstate accounting
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*/
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void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
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{
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u64 state_time;
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struct vcpu_runstate_info *state;
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BUG_ON(preemptible());
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state = this_cpu_ptr(&xen_runstate);
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/*
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* The runstate info is always updated by the hypervisor on
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* the current CPU, so there's no need to use anything
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* stronger than a compiler barrier when fetching it.
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*/
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do {
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state_time = get64(&state->state_entry_time);
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*res = READ_ONCE(*state);
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} while (get64(&state->state_entry_time) != state_time);
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}
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/* return true when a vcpu could run but has no real cpu to run on */
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bool xen_vcpu_stolen(int vcpu)
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{
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return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
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}
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void xen_setup_runstate_info(int cpu)
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{
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struct vcpu_register_runstate_memory_area area;
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area.addr.v = &per_cpu(xen_runstate, cpu);
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if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
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cpu, &area))
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BUG();
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}
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