KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/drivers/dma/dw/acpi.c b/drivers/dma/dw/acpi.c
new file mode 100644
index 000000000..b6452fffa
--- /dev/null
+++ b/drivers/dma/dw/acpi.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2013,2019 Intel Corporation
+
+#include <linux/acpi.h>
+#include <linux/acpi_dma.h>
+
+#include "internal.h"
+
+static bool dw_dma_acpi_filter(struct dma_chan *chan, void *param)
+{
+	struct dw_dma *dw = to_dw_dma(chan->device);
+	struct dw_dma_chip_pdata *data = dev_get_drvdata(dw->dma.dev);
+	struct acpi_dma_spec *dma_spec = param;
+	struct dw_dma_slave slave = {
+		.dma_dev = dma_spec->dev,
+		.src_id = dma_spec->slave_id,
+		.dst_id = dma_spec->slave_id,
+		.m_master = data->m_master,
+		.p_master = data->p_master,
+	};
+
+	return dw_dma_filter(chan, &slave);
+}
+
+void dw_dma_acpi_controller_register(struct dw_dma *dw)
+{
+	struct device *dev = dw->dma.dev;
+	struct acpi_dma_filter_info *info;
+	int ret;
+
+	if (!has_acpi_companion(dev))
+		return;
+
+	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return;
+
+	dma_cap_zero(info->dma_cap);
+	dma_cap_set(DMA_SLAVE, info->dma_cap);
+	info->filter_fn = dw_dma_acpi_filter;
+
+	ret = acpi_dma_controller_register(dev, acpi_dma_simple_xlate, info);
+	if (ret)
+		dev_err(dev, "could not register acpi_dma_controller\n");
+}
+EXPORT_SYMBOL_GPL(dw_dma_acpi_controller_register);
+
+void dw_dma_acpi_controller_free(struct dw_dma *dw)
+{
+	struct device *dev = dw->dma.dev;
+
+	if (!has_acpi_companion(dev))
+		return;
+
+	acpi_dma_controller_free(dev);
+}
+EXPORT_SYMBOL_GPL(dw_dma_acpi_controller_free);