linux-kernel - [PATCH v3] PCI: Equalize hotplug memory and io for non/occupied slots

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Message-Id: <1537900746-3043-1-git-send-email-jonathan.derrick@intel.com>
Date:   Tue, 25 Sep 2018 12:39:06 -0600
From:   Jon Derrick <jonathan.derrick@...el.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sinan Kaya <okaya@...nel.org>, Christoph Hellwig <hch@....de>,
        Keith Busch <keith.busch@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jon Derrick <jonathan.derrick@...el.com>
Subject: [PATCH v3] PCI: Equalize hotplug memory and io for non/occupied slots

Currently, a hotplug bridge will be given hpmemsize additional memory
and hpiosize additional io if available, in order to satisfy any future
hotplug allocation requirements.

These calculations don't consider the current memory/io size of the
hotplug bridge/slot, so hotplug bridges/slots which have downstream
devices will be allocated their current allocation in addition to the
hpmemsize value.

This makes for possibly undesirable results with a mix of unoccupied and
occupied slots (ex, with hpmemsize=2M):

02:03.0 PCI bridge: <-- Occupied
	Memory behind bridge: d6200000-d64fffff [size=3M]
02:04.0 PCI bridge: <-- Unoccupied
	Memory behind bridge: d6500000-d66fffff [size=2M]

This change considers the current allocation size when using the
hpmemsize/hpiosize parameters to make the reservations predictable for
the mix of unoccupied and occupied slots:

02:03.0 PCI bridge: <-- Occupied
	Memory behind bridge: d6200000-d63fffff [size=2M]
02:04.0 PCI bridge: <-- Unoccupied
	Memory behind bridge: d6400000-d65fffff [size=2M]

Signed-off-by: Jon Derrick <jonathan.derrick@...el.com>
---
v2->v3: Made the IO and mem size calculations nearly equivalent

 drivers/pci/setup-bus.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 79b1824..ed96043 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -811,6 +811,8 @@ static struct resource *find_free_bus_resource(struct pci_bus *bus,
 static resource_size_t calculate_iosize(resource_size_t size,
 		resource_size_t min_size,
 		resource_size_t size1,
+		resource_size_t add_size,
+		resource_size_t children_add_size,
 		resource_size_t old_size,
 		resource_size_t align)
 {
@@ -823,15 +825,18 @@ static resource_size_t calculate_iosize(resource_size_t size,
 #if defined(CONFIG_ISA) || defined(CONFIG_EISA)
 	size = (size & 0xff) + ((size & ~0xffUL) << 2);
 #endif
-	size = ALIGN(size + size1, align);
+	size = size + size1;
 	if (size < old_size)
 		size = old_size;
+
+	size = ALIGN(max(size, add_size) + children_add_size, align);
 	return size;
 }
 
 static resource_size_t calculate_memsize(resource_size_t size,
 		resource_size_t min_size,
-		resource_size_t size1,
+		resource_size_t add_size,
+		resource_size_t children_add_size,
 		resource_size_t old_size,
 		resource_size_t align)
 {
@@ -841,7 +846,8 @@ static resource_size_t calculate_memsize(resource_size_t size,
 		old_size = 0;
 	if (size < old_size)
 		size = old_size;
-	size = ALIGN(size + size1, align);
+
+	size = ALIGN(max(size, add_size) + children_add_size, align);
 	return size;
 }
 
@@ -930,12 +936,10 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
 		}
 	}
 
-	size0 = calculate_iosize(size, min_size, size1,
+	size0 = calculate_iosize(size, min_size, size1, 0, 0,
 			resource_size(b_res), min_align);
-	if (children_add_size > add_size)
-		add_size = children_add_size;
-	size1 = (!realloc_head || (realloc_head && !add_size)) ? size0 :
-		calculate_iosize(size, min_size, add_size + size1,
+	size1 = (!realloc_head || (realloc_head && !add_size && !children_add_size)) ? size0 :
+		calculate_iosize(size, min_size, size1, add_size, children_add_size,
 			resource_size(b_res), min_align);
 	if (!size0 && !size1) {
 		if (b_res->start || b_res->end)
@@ -1079,12 +1083,10 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 
 	min_align = calculate_mem_align(aligns, max_order);
 	min_align = max(min_align, window_alignment(bus, b_res->flags));
-	size0 = calculate_memsize(size, min_size, 0, resource_size(b_res), min_align);
+	size0 = calculate_memsize(size, min_size, 0, 0, resource_size(b_res), min_align);
 	add_align = max(min_align, add_align);
-	if (children_add_size > add_size)
-		add_size = children_add_size;
-	size1 = (!realloc_head || (realloc_head && !add_size)) ? size0 :
-		calculate_memsize(size, min_size, add_size,
+	size1 = (!realloc_head || (realloc_head && !add_size && !children_add_size)) ? size0 :
+		calculate_memsize(size, min_size, add_size, children_add_size,
 				resource_size(b_res), add_align);
 	if (!size0 && !size1) {
 		if (b_res->start || b_res->end)
-- 
1.8.3.1