Ovmf/Xen: port XenBusDxe to other architectures

This patch updates XenBusDxe to use the 16-bit compare and exchange
function that was introduced for this purpose to the
BaseSynchronizationLib. It also provides a new generic implementation
of TestAndClearBit () using the same 16-bit compare and exchange, making
this module fully architecture agnostic.

Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16975 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
Ard Biesheuvel
2015-02-28 20:33:34 +00:00
committed by lersek
parent b94c3ac93d
commit e482753b33
10 changed files with 49 additions and 197 deletions

View File

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/** @file
Implementation of TestAndClearBit using compare-exchange primitive
Copyright (C) 2015, Linaro Ltd.
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution. The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/
#include <Base.h>
#include <Library/SynchronizationLib.h>
INT32
EFIAPI
TestAndClearBit (
IN INT32 Bit,
IN VOID *Address
)
{
UINT16 Word, Read;
UINT16 Mask;
//
// Calculate the effective address relative to 'Address' based on the
// higher order bits of 'Bit'. Use signed shift instead of division to
// ensure we round towards -Inf, and end up with a positive shift in
// 'Bit', even if 'Bit' itself is negative.
//
Address += (Bit >> 4) * sizeof(UINT16);
Mask = 1U << (Bit & 15);
for (Word = *(UINT16 *) Address; Word & Mask; Word = Read) {
Read = InterlockedCompareExchange16 (Address, Word, Word & ~Mask);
if (Read == Word) {
return 1;
}
}
return 0;
}