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, 73 insertions, 0 deletions

diff --git a/drivers/scsi/sd_dif.c b/drivers/scsi/sd_dif.c
new file mode 100644
index 000000000..ff4217fef
--- /dev/null
+++ b/drivers/scsi/sd_dif.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sd_dif.c - SCSI Data Integrity Field
+ *
+ * Copyright (C) 2007, 2008 Oracle Corporation
+ * Written by: Martin K. Petersen <martin.petersen@oracle.com>
+ */
+
+#include <linux/blk-integrity.h>
+#include <linux/t10-pi.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_dbg.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_driver.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_ioctl.h>
+#include <scsi/scsicam.h>
+
+#include "sd.h"
+
+/*
+ * Configure exchange of protection information between OS and HBA.
+ */
+void sd_dif_config_host(struct scsi_disk *sdkp, struct queue_limits *lim)
+{
+	struct scsi_device *sdp = sdkp->device;
+	u8 type = sdkp->protection_type;
+	struct blk_integrity *bi = &lim->integrity;
+	int dif, dix;
+
+	memset(bi, 0, sizeof(*bi));
+
+	dif = scsi_host_dif_capable(sdp->host, type);
+	dix = scsi_host_dix_capable(sdp->host, type);
+
+	if (!dix && scsi_host_dix_capable(sdp->host, 0)) {
+		dif = 0; dix = 1;
+	}
+
+	if (!dix)
+		return;
+
+	/* Enable DMA of protection information */
+	if (scsi_host_get_guard(sdkp->device->host) & SHOST_DIX_GUARD_IP)
+		bi->csum_type = BLK_INTEGRITY_CSUM_IP;
+	else
+		bi->csum_type = BLK_INTEGRITY_CSUM_CRC;
+
+	if (type != T10_PI_TYPE3_PROTECTION)
+		bi->flags |= BLK_INTEGRITY_REF_TAG;
+
+	bi->metadata_size = sizeof(struct t10_pi_tuple);
+	bi->pi_tuple_size = bi->metadata_size;
+
+	if (dif && type) {
+		bi->flags |= BLK_INTEGRITY_DEVICE_CAPABLE;
+
+		if (!sdkp->ATO)
+			return;
+
+		if (type == T10_PI_TYPE3_PROTECTION)
+			bi->tag_size = sizeof(u16) + sizeof(u32);
+		else
+			bi->tag_size = sizeof(u16);
+	}
+
+	sd_first_printk(KERN_NOTICE, sdkp,
+			"Enabling DIX %s, application tag size %u bytes\n",
+			blk_integrity_profile_name(bi), bi->tag_size);
+}