[PATCH v3 5/7] x86/dma/amd-gart: Stop resizing dma_debug_entry pool

From: Robin Murphy
Date: Mon Dec 10 2018 - 09:01:06 EST

dma-debug is now capable of adding new entries to its pool on-demand if
the initial preallocation was insufficient, so the IOMMU_LEAK logic no
longer needs to explicitly change the pool size. This does lose it the
ability to save a couple of megabytes of RAM by reducing the pool size
below its default, but it seems unlikely that that is a realistic
concern these days (or indeed that anyone is actively debugging AGP
drivers' DMA usage any more). Getting rid of dma_debug_resize_entries()
will make room for further streamlining in the dma-debug code itself.

Removing the call reveals quite a lot of cruft which has been useless
for nearly a decade since commit 19c1a6f5764d ("x86 gart: reimplement
IOMMU_LEAK feature by using DMA_API_DEBUG"), including the entire
'iommu=leak' parameter, which controlled nothing except whether
dma_debug_resize_entries() was called or not.

CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Borislav Petkov <bp@xxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: x86@xxxxxxxxxx
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>

v3: Add Christoph's review tag

Documentation/x86/x86_64/boot-options.txt | 5 +----
arch/x86/kernel/amd_gart_64.c | 23 -----------------------
2 files changed, 1 insertion(+), 27 deletions(-)

diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
index ad6d2a80cf05..abc53886655e 100644
--- a/Documentation/x86/x86_64/boot-options.txt
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -209,7 +209,7 @@ IOMMU (input/output memory management unit)
mapping with memory protection, etc.
Kernel boot message: "PCI-DMA: Using Calgary IOMMU"

- iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>]
+ iommu=[<size>][,noagp][,off][,force][,noforce]

@@ -228,9 +228,6 @@ IOMMU (input/output memory management unit)
allowed Overwrite iommu off workarounds for specific chipsets.
fullflush Flush IOMMU on each allocation (default).
nofullflush Don't use IOMMU fullflush.
- leak Turn on simple iommu leak tracing (only when
- CONFIG_IOMMU_LEAK is on). Default number of leak pages
- is 20.
memaper[=<order>] Allocate an own aperture over RAM with size 32MB<<order.
(default: order=1, i.e. 64MB)
merge Do scatter-gather (SG) merging. Implies "force"
diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index 3f9d1b4019bb..aa7706bf4d25 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -155,9 +155,6 @@ static void flush_gart(void)

/* Debugging aid for drivers that don't free their IOMMU tables */
-static int leak_trace;
-static int iommu_leak_pages = 20;
static void dump_leak(void)
static int dump;
@@ -774,16 +771,6 @@ int __init gart_iommu_init(void)
if (!iommu_gart_bitmap)
panic("Cannot allocate iommu bitmap\n");

- if (leak_trace) {
- int ret;
- ret = dma_debug_resize_entries(iommu_pages);
- if (ret)
- pr_debug("PCI-DMA: Cannot trace all the entries\n");
- }
* Out of IOMMU space handling.
* Reserve some invalid pages at the beginning of the GART.
@@ -853,16 +840,6 @@ void __init gart_parse_options(char *p)
int arg;

- if (!strncmp(p, "leak", 4)) {
- leak_trace = 1;
- p += 4;
- if (*p == '=')
- ++p;
- if (isdigit(*p) && get_option(&p, &arg))
- iommu_leak_pages = arg;
- }
if (isdigit(*p) && get_option(&p, &arg))
iommu_size = arg;
if (!strncmp(p, "fullflush", 9))