[PATCH RFC v2 26/50] samples/kvm: Remove fixed address and length module parameters

[Ackerley Tng via B4 Relay <devnull+ackerleytng.google.com@kernel.org>]

From: Ackerley Tng <ackerleytng@google.com>

Remove the addr and len module parameters from the sample memory
provider.

The prototype doesn't require pre-carved out memory ranges, since
MPS_NEW_CHILD already allows carving out memory on the fly. Being able to
carve out memory on the fly makes testing easier.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 samples/Kconfig                   | 12 +++------
 samples/kvm/mem_provider_sample.c | 53 +++++++++------------------------------
 2 files changed, 15 insertions(+), 50 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 3c870bca076af..a06eafb5d7ba4 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -331,15 +331,9 @@ config SAMPLE_KVM_MEM_PROVIDER
 	depends on MEM_PROVIDER && CONTIG_ALLOC && X86_64 && m
 	help
 	  This builds a sample memory provider (include/linux/mem_provider.h).
-	  Its files can back a guest_memfd and be mapped by iommufd.  Loaded
-	  with addr= and len=, it lends a fixed physical range that has no
-	  struct page, for example memory hidden with memmap= on the command
-	  line.  Without them, it allocates a contiguous region with
-	  alloc_contig_pages().
-
-	  It shows how a memory owner moves pages between VMs, takes them
-	  back or makes them read only, and how guest_memfd and iommufd
-	  follow each change.
+	  Its files can back a guest_memfd and be mapped by iommufd.
+	  It allocates a contiguous region with alloc_contig_pages()
+	  and carves out child provider files on the fly.
 
 	  If unsure, say N.
 
diff --git a/samples/kvm/mem_provider_sample.c b/samples/kvm/mem_provider_sample.c
index f7ecb2ea1d75d..574c712a11389 100644
--- a/samples/kvm/mem_provider_sample.c
+++ b/samples/kvm/mem_provider_sample.c
@@ -8,17 +8,9 @@
  * guest's devices.  The module calls neither KVM nor iommufd: it answers
  * "what is page N" and revokes a range when the answer changes.
  *
- * The region is either:
- *
- *  - a fixed range given with addr= and len=, which has no struct page, for
- *    example memory hidden from the kernel with memmap= on the command line;
- *  - or, without those parameters, a range from alloc_contig_pages().
- *
  * The control device /dev/mem_provider_sample creates provider files.
- * SETUP makes one file over the whole region.  NEW_CHILD carves part of the
- * region into a child file, and MOVE, DONATE and RECLAIM change which child
- * has which page.  A page can also be taken away or made read only.  See
- * mem_provider_sample.h.
+ * NEW_CHILD carves part of the region into a child file. A page can also
+ * be taken away. See mem_provider_sample.h.
  *
  * Confidential VMs are not supported.
  */
@@ -38,15 +30,6 @@
 
 #include "mem_provider_sample.h"
 
-static unsigned long long addr;
-module_param(addr, ullong, 0444);
-MODULE_PARM_DESC(addr,
-		 "Physical base of a region with no struct page (optional)");
-
-static unsigned long long len;
-module_param(len, ullong, 0444);
-MODULE_PARM_DESC(len, "Size in bytes of that region (optional)");
-
 /*
  * One provider file.
  *
@@ -314,32 +297,26 @@ static struct page *mps_alloc_region(unsigned long npages)
 
 /* ---- Root and children -------------------------------------------------- */
 
-/* Create the root on the first NEW_CHILD, from addr=/len= or of @size. */
+/* Create the root on the first NEW_CHILD of @size. */
 static int mps_root_ensure(u64 size)
 {
-	struct page *pages = NULL;
+	struct page *pages;
 	unsigned long npages;
 
 	lockdep_assert_held(&mps_root.lock);
 	if (mps_root.npages)
 		return 0;
 
-	if (addr && len) {
-		mps_root.base_pfn = addr >> PAGE_SHIFT;
-		npages = len >> PAGE_SHIFT;
-	} else {
-		if (!size || !PAGE_ALIGNED(size))
-			return -EINVAL;
-		npages = size >> PAGE_SHIFT;
-		pages = mps_alloc_region(npages);
-		if (!pages)
-			return -ENOMEM;
-		mps_root.base_pfn = page_to_pfn(pages);
-	}
+	if (!size || !PAGE_ALIGNED(size))
+		return -EINVAL;
+	npages = size >> PAGE_SHIFT;
+	pages = mps_alloc_region(npages);
+	if (!pages)
+		return -ENOMEM;
+	mps_root.base_pfn = page_to_pfn(pages);
 	mps_root.allocated = bitmap_zalloc(npages, GFP_KERNEL);
 	if (!mps_root.allocated) {
-		if (pages)
-			free_contig_range(page_to_pfn(pages), npages);
+		free_contig_range(page_to_pfn(pages), npages);
 		return -ENOMEM;
 	}
 	mps_root.cma_pages = pages;
@@ -489,12 +466,6 @@ static int __init mps_init(void)
 {
 	int ret;
 
-	if ((addr || len) &&
-	    (!addr || !len || !PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len))) {
-		pr_err("mem_provider_sample: addr= and len= must both be set and page aligned\n");
-		return -EINVAL;
-	}
-
 	mutex_init(&mps_root.lock);
 	INIT_LIST_HEAD(&mps_root.children);
 

-- 
2.56.0.257.gf7497c7d27-goog