lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 17 Nov 2014 09:18:40 -0800
From:	Alexander Duyck <alexander.h.duyck@...hat.com>
To:	linux-arch@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	mathieu.desnoyers@...ymtl.ca, peterz@...radead.org,
	benh@...nel.crashing.org, heiko.carstens@...ibm.com,
	mingo@...nel.org, mikey@...ling.org, linux@....linux.org.uk,
	donald.c.skidmore@...el.com, matthew.vick@...el.com,
	geert@...ux-m68k.org, jeffrey.t.kirsher@...el.com,
	romieu@...zoreil.com, paulmck@...ux.vnet.ibm.com,
	nic_swsd@...ltek.com, will.deacon@....com, michael@...erman.id.au,
	tony.luck@...el.com, torvalds@...ux-foundation.org,
	oleg@...hat.com, schwidefsky@...ibm.com, fweisbec@...il.com,
	davem@...emloft.net
Subject: [PATCH 4/4] fm10k/igb/ixgbe: Use fast_rmb on Rx descriptor reads

This change makes it so that fast_rmb is used when reading the Rx
descriptor.  The advantage of fast_rmb is that it allows for a much
lower cost barrier on x86, powerpc, arm, and arm64 architectures than a
traditional memory barrier when dealing with reads that only have to
synchronize to system memory.

In addition I have updated the code so that it just checks to see if any
bits have been set instead of just the DD bit since the DD bit will always
be set as a part of a descriptor write-back so we just need to check for a
non-zero value being present at that memory location rather than just
checking for any specific bit.  This allows the code itself to appear much
cleaner and allows the compiler more room to optimize.

Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc: Matthew Vick <matthew.vick@...el.com>
Cc: Don Skidmore <donald.c.skidmore@...el.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@...hat.com>
---
 drivers/net/ethernet/intel/fm10k/fm10k_main.c |    6 +++---
 drivers/net/ethernet/intel/igb/igb_main.c     |    6 +++---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |    9 ++++-----
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_main.c b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
index e645af4..ba959b9 100644
--- a/drivers/net/ethernet/intel/fm10k/fm10k_main.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
@@ -620,14 +620,14 @@ static bool fm10k_clean_rx_irq(struct fm10k_q_vector *q_vector,
 
 		rx_desc = FM10K_RX_DESC(rx_ring, rx_ring->next_to_clean);
 
-		if (!fm10k_test_staterr(rx_desc, FM10K_RXD_STATUS_DD))
+		if (!rx_desc->d.staterr)
 			break;
 
 		/* This memory barrier is needed to keep us from reading
 		 * any other fields out of the rx_desc until we know the
-		 * RXD_STATUS_DD bit is set
+		 * descriptor has been written back
 		 */
-		rmb();
+		fast_rmb();
 
 		/* retrieve a buffer from the ring */
 		skb = fm10k_fetch_rx_buffer(rx_ring, rx_desc, skb);
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index a2d72a8..3dbbaa8 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6918,14 +6918,14 @@ static bool igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
 
 		rx_desc = IGB_RX_DESC(rx_ring, rx_ring->next_to_clean);
 
-		if (!igb_test_staterr(rx_desc, E1000_RXD_STAT_DD))
+		if (!rx_desc->wb.upper.status_error)
 			break;
 
 		/* This memory barrier is needed to keep us from reading
 		 * any other fields out of the rx_desc until we know the
-		 * RXD_STAT_DD bit is set
+		 * descriptor has been written back
 		 */
-		rmb();
+		fast_rmb();
 
 		/* retrieve a buffer from the ring */
 		skb = igb_fetch_rx_buffer(rx_ring, rx_desc, skb);
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index d2df4e3..890d740 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -2003,15 +2003,14 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
 
 		rx_desc = IXGBE_RX_DESC(rx_ring, rx_ring->next_to_clean);
 
-		if (!ixgbe_test_staterr(rx_desc, IXGBE_RXD_STAT_DD))
+		if (!rx_desc->wb.upper.status_error)
 			break;
 
-		/*
-		 * This memory barrier is needed to keep us from reading
+		/* This memory barrier is needed to keep us from reading
 		 * any other fields out of the rx_desc until we know the
-		 * RXD_STAT_DD bit is set
+		 * descriptor has been written back
 		 */
-		rmb();
+		fast_rmb();
 
 		/* retrieve a buffer from the ring */
 		skb = ixgbe_fetch_rx_buffer(rx_ring, rx_desc);

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists