linux-kernel - [PATCH 1/1] drivers:hv: Allow for MMIO claims that span ACPI

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Message-Id: <1447104632-12560-1-git-send-email-jakeo@microsoft.com>
Date:	Mon,  9 Nov 2015 21:30:32 +0000
From:	jakeo@...rosoft.com
To:	gregkh@...uxfoundation.org, kys@...rosoft.com,
	linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
	olaf@...fle.de, apw@...onical.com, vkuznets@...hat.com
Cc:	Jake Oshins <jakeo@...rosoft.com>
Subject: [PATCH 1/1] drivers:hv: Allow for MMIO claims that span ACPI _CRS records

From: Jake Oshins <jakeo@...rosoft.com>

This patch makes 16GB GPUs work in Hyper-V VMs, since, for
compatibility reasons, the Hyper-V BIOS lists MMIO ranges in 2GB
chunks in its root bus's _CRS object.

Signed-off-by: Jake Oshins <jakeo@...rosoft.com>
---
 drivers/hv/vmbus_drv.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index c89d0e5..aef5fae 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1075,12 +1075,28 @@ static acpi_status vmbus_walk_resources(struct acpi_resource *res, void *ctx)
 	new_res->start = start;
 	new_res->end = end;
 
+	/*
+	 * Stick ranges from higher in address space at the front of the list.
+	 * If two ranges are adjacent, merge them.
+	 */
 	do {
 		if (!*old_res) {
 			*old_res = new_res;
 			break;
 		}
 
+		if (((*old_res)->end + 1) == new_res->start) {
+			(*old_res)->end = new_res->end;
+			kfree(new_res);
+			break;
+		}
+
+		if ((*old_res)->start == new_res->end + 1) {
+			(*old_res)->start = new_res->start;
+			kfree(new_res);
+			break;
+		}
+
 		if ((*old_res)->end < new_res->start) {
 			new_res->sibling = *old_res;
 			if (prev_res)
-- 
1.9.1

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