Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Arvind Sankar <nivedita@alum.mit.edu>
To:     Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Ard Biesheuvel <ardb@kernel.org>, linux-efi@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 3/4] x86/mm/pat: Propagate all errors out of populate_pud
Date:   Tue,  3 Mar 2020 15:54:44 -0500
Message-Id: <20200303205445.3965393-4-nivedita@alum.mit.edu>
In-Reply-To: <20200303205445.3965393-1-nivedita@alum.mit.edu>
References: <20200303205445.3965393-1-nivedita@alum.mit.edu>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

populate_pud tries to return the number of pages mapped so far if
populate_pmd fails. This is of dubious utility, since if populate_pmd
did any work before failing, the returned number of pages will be
inconsistent with cpa->pfn, and the loop in __change_page_attr_set_clr
will retry with that inconsistent state. Further, if the number of pages
mapped before failure is zero, that will trigger the BUG_ON in
__change_page_attr_set_clr.

Just return all errors up the stack and let the original caller deal
with it.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 arch/x86/mm/pat/set_memory.c | 43 ++++++++++++++++--------------------
 1 file changed, 19 insertions(+), 24 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index a1003bc9fdf6..2f98423ef69a 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1247,9 +1247,9 @@ static void populate_pte(struct cpa_data *cpa,
 	}
 }
 
-static long populate_pmd(struct cpa_data *cpa,
-			 unsigned long start, unsigned long end,
-			 unsigned num_pages, pud_t *pud, pgprot_t pgprot)
+static int populate_pmd(struct cpa_data *cpa,
+			unsigned long start, unsigned long end,
+			unsigned num_pages, pud_t *pud, pgprot_t pgprot)
 {
 	long cur_pages = 0;
 	pmd_t *pmd;
@@ -1283,7 +1283,7 @@ static long populate_pmd(struct cpa_data *cpa,
 	 * We mapped them all?
 	 */
 	if (num_pages == cur_pages)
-		return cur_pages;
+		return 0;
 
 	pmd_pgprot = pgprot_4k_2_large(pgprot);
 
@@ -1318,7 +1318,7 @@ static long populate_pmd(struct cpa_data *cpa,
 		populate_pte(cpa, start, end, num_pages - cur_pages,
 			     pmd, pgprot);
 	}
-	return num_pages;
+	return 0;
 }
 
 static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
@@ -1328,6 +1328,7 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 	unsigned long end;
 	long cur_pages = 0;
 	pgprot_t pud_pgprot;
+	int ret;
 
 	end = start + (cpa->numpages << PAGE_SHIFT);
 
@@ -1352,17 +1353,16 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 			if (alloc_pmd_page(pud))
 				return -1;
 
-		cur_pages = populate_pmd(cpa, start, pre_end, cur_pages,
-					 pud, pgprot);
-		if (cur_pages < 0)
-			return cur_pages;
+		ret = populate_pmd(cpa, start, pre_end, cur_pages, pud, pgprot);
+		if (ret < 0)
+			return ret;
 
 		start = pre_end;
 	}
 
 	/* We mapped them all? */
 	if (cpa->numpages == cur_pages)
-		return cur_pages;
+		return 0;
 
 	pud = pud_offset(p4d, start);
 	pud_pgprot = pgprot_4k_2_large(pgprot);
@@ -1379,10 +1379,10 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 			if (pud_none(*pud))
 				if (alloc_pmd_page(pud))
 					return -1;
-			if (populate_pmd(cpa, start, start + PUD_SIZE,
-					 PUD_SIZE >> PAGE_SHIFT,
-					 pud, pgprot) < 0)
-				return cur_pages;
+			ret = populate_pmd(cpa, start, start + PUD_SIZE,
+					   PUD_SIZE >> PAGE_SHIFT, pud, pgprot);
+			if (ret < 0)
+				return ret;
 		}
 
 		start	  += PUD_SIZE;
@@ -1392,21 +1392,17 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 
 	/* Map trailing leftover */
 	if (start < end) {
-		long tmp;
-
 		pud = pud_offset(p4d, start);
 		if (pud_none(*pud))
 			if (alloc_pmd_page(pud))
 				return -1;
 
-		tmp = populate_pmd(cpa, start, end, cpa->numpages - cur_pages,
+		ret = populate_pmd(cpa, start, end, cpa->numpages - cur_pages,
 				   pud, pgprot);
-		if (tmp < 0)
-			return cur_pages;
-
-		cur_pages += tmp;
+		if (ret < 0)
+			return ret;
 	}
-	return cur_pages;
+	return 0;
 }
 
 /*
@@ -1419,7 +1415,7 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	pud_t *pud = NULL;	/* shut up gcc */
 	p4d_t *p4d;
 	pgd_t *pgd_entry;
-	long ret;
+	int ret;
 	unsigned long end, end_p4d;
 
 	pgd_entry = cpa->pgd + pgd_index(addr);
@@ -1468,7 +1464,6 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 		return ret;
 	}
 
-	cpa->numpages = ret;
 	return 0;
 }
 
-- 
2.24.1