linux-kernel - Re: [Xen-devel] [PATCH] PVH linux: Use ballooning to allocate grant table pages

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Message-ID: <20130131184446.654a2289@mantra.us.oracle.com>
Date:	Thu, 31 Jan 2013 18:44:46 -0800
From:	Mukesh Rathor <mukesh.rathor@...cle.com>
To:	Mukesh Rathor <mukesh.rathor@...cle.com>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"Xen-devel@...ts.xensource.com" <Xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"stefano.stabellini@...citrix.com" <stefano.stabellini@...citrix.com>
Subject: Re: [Xen-devel] [PATCH] PVH linux: Use ballooning to allocate grant
 table pages

On Thu, 31 Jan 2013 18:30:15 -0800
Mukesh Rathor <mukesh.rathor@...cle.com> wrote:

> This patch fixes a fixme in Linux to use alloc_xenballooned_pages() to
> allocate pfns for grant table pages instead of kmalloc. This also
> simplifies add to physmap on the xen side a bit.

Looking at it again, I realized rc should be signed in gnttab_resume().
Below again. Thanks.

Signed-off-by: Mukesh Rathor <mukesh.rathor@...cle.com>

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 9c0019d..7a630bb 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -47,6 +47,7 @@
 #include <xen/grant_table.h>
 #include <xen/interface/memory.h>
 #include <xen/hvc-console.h>
+#include <xen/balloon.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/interface.h>
 
@@ -1138,27 +1139,42 @@ static void gnttab_request_version(void)
 		grant_table_version);
 }
 
+static int xlated_setup_gnttab_pages(int numpages, void **addr)
+{
+	int i, rc;
+	unsigned long pfns[numpages];
+	struct page *pages[numpages];
+
+	rc = alloc_xenballooned_pages(numpages, pages, 0);
+	if (rc != 0) {
+		pr_warn("%s Could not balloon alloc %d pfns rc:%d\n", __func__,
+			numpages, rc);
+		return -ENOMEM;
+	}
+	for (i = 0; i < numpages; i++)
+		pfns[i] = page_to_pfn(pages[i]);
+
+	rc = arch_gnttab_map_shared(pfns, numpages, numpages, addr);
+	return rc;
+}
+
 int gnttab_resume(void)
 {
+	int rc;
 	unsigned int max_nr_gframes;
-	char *kmsg = "Failed to kmalloc pages for pv in hvm grant frames\n";
 
 	gnttab_request_version();
 	max_nr_gframes = gnttab_max_grant_frames();
 	if (max_nr_gframes < nr_grant_frames)
 		return -ENOSYS;
 
-	/* PVH note: xen will free existing kmalloc'd mfn in
-	 * XENMEM_add_to_physmap. TBD/FIXME: use xen ballooning instead of
-	 * kmalloc(). */
 	if (xen_pv_domain() && xen_feature(XENFEAT_auto_translated_physmap) &&
 	    !gnttab_shared.addr) {
-		gnttab_shared.addr =
-			kmalloc(max_nr_gframes * PAGE_SIZE, GFP_KERNEL);
-		if (!gnttab_shared.addr) {
-			pr_warn("%s", kmsg);
-			return -ENOMEM;
-		}
+
+		rc = xlated_setup_gnttab_pages(max_nr_gframes,
+					       &gnttab_shared.addr);
+		if (rc != 0)
+			return rc;
 	}
 	if (xen_pv_domain())
 		return gnttab_map(0, nr_grant_frames - 1);



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