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On POWER9 and newer, rather than the complex HMI synchronisation and subcore state, have each thread un-apply the guest TB offset before calling into the early HMI handler. This allows the subcore state to be avoided, including subcore enter / exit guest, which includes an expensive divide that shows up slightly in profiles. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211123095231.1036501-54-npiggin@gmail.com
51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Hypervisor Maintenance Interrupt (HMI) handling.
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*
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* Copyright 2015 IBM Corporation
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* Author: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
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*/
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#undef DEBUG
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#include <linux/types.h>
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#include <linux/compiler.h>
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#include <asm/paca.h>
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#include <asm/hmi.h>
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#include <asm/processor.h>
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void wait_for_subcore_guest_exit(void)
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{
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int i;
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/*
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* NULL bitmap pointer indicates that KVM module hasn't
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* been loaded yet and hence no guests are running, or running
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* on POWER9 or newer CPU.
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*
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* If no KVM is in use, no need to co-ordinate among threads
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* as all of them will always be in host and no one is going
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* to modify TB other than the opal hmi handler.
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*
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* POWER9 and newer don't need this synchronisation.
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*
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* Hence, just return from here.
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*/
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if (!local_paca->sibling_subcore_state)
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return;
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for (i = 0; i < MAX_SUBCORE_PER_CORE; i++)
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while (local_paca->sibling_subcore_state->in_guest[i])
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cpu_relax();
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}
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void wait_for_tb_resync(void)
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{
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if (!local_paca->sibling_subcore_state)
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return;
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while (test_bit(CORE_TB_RESYNC_REQ_BIT,
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&local_paca->sibling_subcore_state->flags))
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cpu_relax();
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}
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