linux-kernel - [65/90] sparc: Dont do expensive hypervisor PCR write unless necessary.

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Message-Id: <20110812210557.805423660@clark.kroah.org>
Date:	Fri, 12 Aug 2011 14:04:50 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	"David S. Miller" <davem@...emloft.net>
Subject: [65/90] sparc: Dont do expensive hypervisor PCR write unless necessary.

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------


From: "David S. Miller" <davem@...emloft.net>

[ Upstream commit 314ff52727fe94dfbe07f3a9a489ab3ca8d8df5a ]

The hypervisor call is only necessary if hypervisor events are
being requested.

So if we're not tracking hypervisor events, simply do a direct
register write.

Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 arch/sparc/kernel/pcr.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/arch/sparc/kernel/pcr.c
+++ b/arch/sparc/kernel/pcr.c
@@ -80,8 +80,11 @@ static void n2_pcr_write(u64 val)
 {
 	unsigned long ret;
 
-	ret = sun4v_niagara2_setperf(HV_N2_PERF_SPARC_CTL, val);
-	if (ret != HV_EOK)
+	if (val & PCR_N2_HTRACE) {
+		ret = sun4v_niagara2_setperf(HV_N2_PERF_SPARC_CTL, val);
+		if (ret != HV_EOK)
+			write_pcr(val);
+	} else
 		write_pcr(val);
 }
 


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