linux-kernel - Re: [PATCH v2] Persistent grant maps for xen blk drivers

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Message-Id: <43E8FEC9-DE7D-4352-87F2-63FB8984D556@gridcentric.ca>
Date:	Mon, 24 Sep 2012 10:38:48 -0400
From:	Andres Lagar-Cavilla <andreslc@...dcentric.ca>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	Oliver Chick <oliver.chick@...rix.com>, xen-devel@...ts.xen.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Persistent grant maps for xen blk drivers

On Sep 21, 2012, at 4:46 PM, Konrad Rzeszutek Wilk wrote:

> On Fri, Sep 21, 2012 at 02:56:22PM -0400, Konrad Rzeszutek Wilk wrote:
>>> *: With a PVHVM guest I get
>>> 
>>> [  261.927218] privcmd_fault: vma=ffff88002a31dce8 7f4edc095000-7f4edc195000, pgoff=c8, uv=00007f4edc15d000
>>> 
>>> thought if I applied your patch on top of v3.6-rc6 I didn't see the privcmd_fault but
>>> I did see the guest crash.
>> 
>> And that is due to c571898ffc24a1768e1b2dabeac0fc7dd4c14601 which I've reverted in my
>> #linux-next branch
> 
> Nevermind. Andres' patch by itself (so without yours) works just fine. There is
> something your patch and his aren't agreeing on.

Apart from interacting badly in combination, would either patch in isolation work well?

I can think of only one hunk in my patch disagreeing with blkback stuff:
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index eea81cf..f5681c8 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -836,6 +883,12 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 	if (ret)
 		return ret;
 
+	/* Retry eagain maps */
+	for (i = 0; i < count; i++)
+		if (map_ops[i].status == GNTST_eagain)
+			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
+                                    &map_ops[i].status, __func__);
+
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return ret;
 
How would you like to proceed?
Andres

> 

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