x86/dma/amd-gart: Stop resizing dma_debug_entry pool

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.

Signed-off-by: Robin Murphy <[e-mail]>
Acked-by: Thomas Gleixner <[e-mail]>
Tested-by: Qian Cai <[e-mail]>
Signed-off-by: Christoph Hellwig <[e-mail]>

Documentation/x86/x86_64/boot-options.txt

···
       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]
 	[,memaper[=<order>]][,merge][,fullflush][,nomerge]
 	[,noaperture][,calgary]
 
···
     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"

arch/x86/kernel/amd_gart_64.c

···
 
 #ifdef CONFIG_IOMMU_LEAK
 /* 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;
···
 	if (!iommu_gart_bitmap)
 		panic("Cannot allocate iommu bitmap\n");
 
-#ifdef CONFIG_IOMMU_LEAK
-	if (leak_trace) {
-		int ret;
-
-		ret = dma_debug_resize_entries(iommu_pages);
-		if (ret)
-			pr_debug("PCI-DMA: Cannot trace all the entries\n");
-	}
-#endif
-
 	pr_info("PCI-DMA: Reserving %luMB of IOMMU area in the AGP aperture\n",
 	       iommu_size >> 20);
 
···
 {
 	int arg;
 
-#ifdef CONFIG_IOMMU_LEAK
-	if (!strncmp(p, "leak", 4)) {
-		leak_trace = 1;
-		p += 4;
-		if (*p == '=')
-			++p;
-		if (isdigit(*p) && get_option(&p, &arg))
-			iommu_leak_pages = arg;
-	}
-#endif
 	if (isdigit(*p) && get_option(&p, &arg))
 		iommu_size = arg;
 	if (!strncmp(p, "fullflush", 9))