[PATCH RFC 08/18] x86/mm/pat: use cpa_split_data structure to pass split parameters

["Mike Rapoport (Microsoft)" <rppt@kernel.org>]

Keeping all split parameters in a struct between
should_split_large_page() and split_large_page() allows maintaining the
split state that is initially established in cpa_handle_large_page(),
then this state is updated in should_split_large_page() and finally
consumed by split_large_page().

Start passing parameters between should_split_large_page() and
split_large_page() in cpa_split_data structure.

As the first step only pass the existing parameters in the new
structure.

No functional change intended.

Assisted-by: Copilot:claude-opus-4.8
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 49 ++++++++++++++++++++++++++++----------------
 1 file changed, 31 insertions(+), 18 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index a9d270e986ff..c2a72cd8b832 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -53,6 +53,15 @@ struct cpa_data {
 	struct page	**pages;
 };
 
+/*
+ * context for checking for a split a large page and splitting it if required.
+ */
+struct cpa_split_data {
+	unsigned long	address;
+	pte_t		*kpte;
+	struct ptdesc	*ptdesc;
+};
+
 enum cpa_warn {
 	CPA_CONFLICT,
 	CPA_PROTECT,
@@ -869,12 +878,14 @@ static pgprot_t pgprot_clear_protnone_bits(pgprot_t prot)
 	return prot;
 }
 
-static int __should_split_large_page(pte_t *kpte, unsigned long address,
-				     struct cpa_data *cpa)
+static int __should_split_large_page(struct cpa_data *cpa,
+				     struct cpa_split_data *sd)
 {
 	unsigned long numpages, pmask, psize, lpaddr, pfn, old_pfn;
 	pgprot_t old_prot, new_prot, req_prot, chk_prot;
+	unsigned long address = sd->address;
 	enum pgtable_level level;
+	pte_t *kpte = sd->kpte;
 	pte_t new_pte, *tmp;
 	bool nx, rw;
 
@@ -1016,8 +1027,8 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
 	return 0;
 }
 
-static int should_split_large_page(pte_t *kpte, unsigned long address,
-				   struct cpa_data *cpa)
+static int should_split_large_page(struct cpa_data *cpa,
+				   struct cpa_split_data *sd)
 {
 	int do_split;
 
@@ -1025,7 +1036,7 @@ static int should_split_large_page(pte_t *kpte, unsigned long address,
 		return 1;
 
 	spin_lock(&pgd_lock);
-	do_split = __should_split_large_page(kpte, address, cpa);
+	do_split = __should_split_large_page(cpa, sd);
 	spin_unlock(&pgd_lock);
 
 	return do_split;
@@ -1067,13 +1078,14 @@ static void split_set_pte(struct cpa_data *cpa, pte_t *pte, unsigned long pfn,
 	set_pte(pte, pfn_pte(pfn, ref_prot));
 }
 
-static int
-__split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
-		   struct ptdesc *ptdesc)
+static int __split_large_page(struct cpa_data *cpa, struct cpa_split_data *sd)
 {
 	unsigned long lpaddr, lpinc, ref_pfn, pfn, pfninc = 1;
+	struct ptdesc *ptdesc = sd->ptdesc;
 	struct page *base = ptdesc_page(ptdesc);
 	pte_t *pbase = (pte_t *)page_address(base);
+	unsigned long address = sd->address;
+	pte_t *kpte = sd->kpte;
 	unsigned int i, level;
 	pgprot_t ref_prot;
 	bool nx, rw;
@@ -1174,19 +1186,16 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
 	return 0;
 }
 
-static int split_large_page(struct cpa_data *cpa, pte_t *kpte,
-			    unsigned long address)
+static int split_large_page(struct cpa_data *cpa, struct cpa_split_data *sd)
 {
-	struct ptdesc *ptdesc;
-
 	spin_unlock(&cpa_lock);
-	ptdesc = pagetable_alloc(GFP_KERNEL, 0);
+	sd->ptdesc = pagetable_alloc(GFP_KERNEL, 0);
 	spin_lock(&cpa_lock);
-	if (!ptdesc)
+	if (!sd->ptdesc)
 		return -ENOMEM;
 
-	if (__split_large_page(cpa, kpte, address, ptdesc))
-		pagetable_free(ptdesc);
+	if (__split_large_page(cpa, sd))
+		pagetable_free(sd->ptdesc);
 
 	return 0;
 }
@@ -1194,13 +1203,17 @@ static int split_large_page(struct cpa_data *cpa, pte_t *kpte,
 static int cpa_handle_large_page(struct cpa_data *cpa, pte_t *kpte,
 				  unsigned long address)
 {
+	struct cpa_split_data sd = {
+		.address = address,
+		.kpte = kpte,
+	};
 	int do_split, err;
 
 	/*
 	 * Check, whether we can keep the large page intact
 	 * and just change the pte:
 	 */
-	do_split = should_split_large_page(kpte, address, cpa);
+	do_split = should_split_large_page(cpa, &sd);
 	/*
 	 * When the range fits into the existing large page, no split is
 	 * required.
@@ -1213,7 +1226,7 @@ static int cpa_handle_large_page(struct cpa_data *cpa, pte_t *kpte,
 	/*
 	 * We have to split the large page:
 	 */
-	err = split_large_page(cpa, kpte, address);
+	err = split_large_page(cpa, &sd);
 	if (err)
 		return err;
 

-- 
2.53.0