From 8fd9a6365eb8a79a2d8f0e0baa01f4db6345e8dd Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Tue, 2 Jul 2013 15:35:13 +0930 Subject: tools/lguest: fix missing rmb(). The virtio spec was missing a barrier in example code, so I went back to look at the lguest code. Indeed, we need one. Signed-off-by: Rusty Russell --- tools/lguest/lguest.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'tools/lguest/lguest.c') diff --git a/tools/lguest/lguest.c b/tools/lguest/lguest.c index 07a03452c227..49ed25b5bbb9 100644 --- a/tools/lguest/lguest.c +++ b/tools/lguest/lguest.c @@ -177,6 +177,7 @@ static struct termios orig_term; * in precise order. */ #define wmb() __asm__ __volatile__("" : : : "memory") +#define rmb() __asm__ __volatile__("" : : : "memory") #define mb() __asm__ __volatile__("" : : : "memory") /* Wrapper for the last available index. Makes it easier to change. */ @@ -676,6 +677,12 @@ static unsigned wait_for_vq_desc(struct virtqueue *vq, errx(1, "Guest moved used index from %u to %u", last_avail, vq->vring.avail->idx); + /* + * Make sure we read the descriptor number *after* we read the ring + * update; don't let the cpu or compiler change the order. + */ + rmb(); + /* * Grab the next descriptor number they're advertising, and increment * the index we've seen. @@ -694,6 +701,12 @@ static unsigned wait_for_vq_desc(struct virtqueue *vq, desc = vq->vring.desc; i = head; + /* + * We have to read the descriptor after we read the descriptor number, + * but there's a data dependency there so the CPU shouldn't reorder + * that: no rmb() required. + */ + /* * If this is an indirect entry, then this buffer contains a descriptor * table which we handle as if it's any normal descriptor chain. -- cgit v1.2.2 From 0d69a65e97fc8090ee83c8639137b4b5c8ece237 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Tue, 2 Jul 2013 15:35:14 +0930 Subject: tools/lguest: real barriers. Lguest guests are UP, but the host is probably SMP, so real barriers are required in case the device thread and the guest are on different CPUs. Signed-off-by: Rusty Russell --- tools/lguest/lguest.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'tools/lguest/lguest.c') diff --git a/tools/lguest/lguest.c b/tools/lguest/lguest.c index 49ed25b5bbb9..a64f5cb0c15b 100644 --- a/tools/lguest/lguest.c +++ b/tools/lguest/lguest.c @@ -177,8 +177,8 @@ static struct termios orig_term; * in precise order. */ #define wmb() __asm__ __volatile__("" : : : "memory") -#define rmb() __asm__ __volatile__("" : : : "memory") -#define mb() __asm__ __volatile__("" : : : "memory") +#define rmb() __asm__ __volatile__("lock; addl $0,0(%%esp)" : : : "memory") +#define mb() __asm__ __volatile__("lock; addl $0,0(%%esp)" : : : "memory") /* Wrapper for the last available index. Makes it easier to change. */ #define lg_last_avail(vq) ((vq)->last_avail_idx) -- cgit v1.2.2 From e6dc0418bcb96e3cccb80571f35934ed72e9c99a Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Thu, 4 Jul 2013 11:22:58 +0930 Subject: lguest: fix example launcher compilation for broken glibc headers. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Somehow a naked u16 slipped into the glibc headers on my Ubuntu machine (i386 2.17-0ubuntu5), breaking compile: In file included from lguest.c:46:0: /usr/include/linux/virtio_net.h:188:2: error: unknown type name ‘u16’ We use the kernel-style types anyway, just define them before the includes. Also remove the advice on adding missing headers: that no longer works. Signed-off-by: Rusty Russell --- tools/lguest/lguest.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) (limited to 'tools/lguest/lguest.c') diff --git a/tools/lguest/lguest.c b/tools/lguest/lguest.c index a64f5cb0c15b..68f67cf3d318 100644 --- a/tools/lguest/lguest.c +++ b/tools/lguest/lguest.c @@ -42,14 +42,6 @@ #include #include -#include -#include -#include -#include -#include -#include -#include -#include "../../include/linux/lguest_launcher.h" /*L:110 * We can ignore the 43 include files we need for this program, but I do want * to draw attention to the use of kernel-style types. @@ -65,6 +57,15 @@ typedef uint16_t u16; typedef uint8_t u8; /*:*/ +#include +#include +#include +#include +#include +#include +#include +#include "../../include/linux/lguest_launcher.h" + #define BRIDGE_PFX "bridge:" #ifndef SIOCBRADDIF #define SIOCBRADDIF 0x89a2 /* add interface to bridge */ -- cgit v1.2.2