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From 0de3b24dc9428a37330f9065bc3626a3a07a9200 Mon Sep 17 00:00:00 2001
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Message-Id: <0de3b24dc9428a37330f9065bc3626a3a07a9200.1387382496.git.minovotn@redhat.com>
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In-Reply-To: <c5386144fbf09f628148101bc674e2421cdd16e3.1387382496.git.minovotn@redhat.com>
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References: <c5386144fbf09f628148101bc674e2421cdd16e3.1387382496.git.minovotn@redhat.com>
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From: Marcelo Tosatti <mtosatti@redhat.com>
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Date: Thu, 12 Dec 2013 01:36:44 +0100
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Subject: [PATCH 46/46] mempath: prefault pages manually (v4)
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RH-Author: Marcelo Tosatti <mtosatti@redhat.com>
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Message-id: <20131212013644.GA8646@amt.cnet>
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Patchwork-id: 56243
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O-Subject: [RHEL7 qemu-kvm PATCH] mempath: prefault pages manually (v4)
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Bugzilla: 1026554
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Igor Mammedov <imammedo@redhat.com>
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RH-Acked-by: Andrew Jones <drjones@redhat.com>
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commit ef36fa1492e9105f3fa607b56edc63df513d7da1 upstream
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v4: s/fail/failed/  (Peter Maydell)
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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BZ: 1026554
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Signed-off-by: Michal Novotny <minovotn@redhat.com>
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---
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 exec.c          | 59 +++++++++++++++++++++++++++++++++++++++++++++------------
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 qemu-options.hx |  2 --
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 vl.c            |  4 ----
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 3 files changed, 47 insertions(+), 18 deletions(-)
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diff --git a/exec.c b/exec.c
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index 64af205..571cea4 100644
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--- a/exec.c
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+++ b/exec.c
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@@ -865,6 +865,13 @@ static long gethugepagesize(const char *path)
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     return fs.f_bsize;
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 }
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+static sigjmp_buf sigjump;
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+
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+static void sigbus_handler(int signal)
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+{
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+    siglongjmp(sigjump, 1);
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+}
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+
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 static void *file_ram_alloc(RAMBlock *block,
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                             ram_addr_t memory,
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                             const char *path)
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@@ -874,9 +881,6 @@ static void *file_ram_alloc(RAMBlock *block,
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     char *c;
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     void *area;
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     int fd;
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-#ifdef MAP_POPULATE
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-    int flags;
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-#endif
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     unsigned long hpagesize;
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     hpagesize = gethugepagesize(path);
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@@ -924,21 +928,52 @@ static void *file_ram_alloc(RAMBlock *block,
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     if (ftruncate(fd, memory))
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         perror("ftruncate");
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-#ifdef MAP_POPULATE
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-    /* NB: MAP_POPULATE won't exhaustively alloc all phys pages in the case
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-     * MAP_PRIVATE is requested.  For mem_prealloc we mmap as MAP_SHARED
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-     * to sidestep this quirk.
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-     */
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-    flags = mem_prealloc ? MAP_POPULATE | MAP_SHARED : MAP_PRIVATE;
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-    area = mmap(0, memory, PROT_READ | PROT_WRITE, flags, fd, 0);
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-#else
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     area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
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-#endif
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     if (area == MAP_FAILED) {
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         perror("file_ram_alloc: can't mmap RAM pages");
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         close(fd);
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         return (NULL);
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     }
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+
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+    if (mem_prealloc) {
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+        int ret, i;
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+        struct sigaction act, oldact;
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+        sigset_t set, oldset;
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+
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+        memset(&act, 0, sizeof(act));
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+        act.sa_handler = &sigbus_handler;
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+        act.sa_flags = 0;
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+
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+        ret = sigaction(SIGBUS, &act, &oldact);
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+        if (ret) {
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+            perror("file_ram_alloc: failed to install signal handler");
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+            exit(1);
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+        }
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+
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+        /* unblock SIGBUS */
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+        sigemptyset(&set);
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+        sigaddset(&set, SIGBUS);
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+        pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
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+
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+        if (sigsetjmp(sigjump, 1)) {
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+            fprintf(stderr, "file_ram_alloc: failed to preallocate pages\n");
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+            exit(1);
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+        }
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+
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+        /* MAP_POPULATE silently ignores failures */
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+        for (i = 0; i < (memory/hpagesize)-1; i++) {
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+            memset(area + (hpagesize*i), 0, 1);
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+        }
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+
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+        ret = sigaction(SIGBUS, &oldact, NULL);
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+        if (ret) {
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+            perror("file_ram_alloc: failed to reinstall signal handler");
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+            exit(1);
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+        }
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+
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+        pthread_sigmask(SIG_SETMASK, &oldset, NULL);
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+    }
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+
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     block->fd = fd;
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     return area;
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 }
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diff --git a/qemu-options.hx b/qemu-options.hx
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index e3c5d67..d9320b5 100644
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--- a/qemu-options.hx
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+++ b/qemu-options.hx
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@@ -228,7 +228,6 @@ STEXI
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 Allocate guest RAM from a temporarily created file in @var{path}.
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 ETEXI
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-#ifdef MAP_POPULATE
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 DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
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     "-mem-prealloc   preallocate guest memory (use with -mem-path)\n",
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     QEMU_ARCH_ALL)
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@@ -237,7 +236,6 @@ STEXI
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 @findex -mem-prealloc
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 Preallocate memory when using -mem-path.
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 ETEXI
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-#endif
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 DEF("k", HAS_ARG, QEMU_OPTION_k,
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     "-k language     use keyboard layout (for example 'fr' for French)\n",
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diff --git a/vl.c b/vl.c
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index 0cbbdf0..da12b90 100644
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--- a/vl.c
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+++ b/vl.c
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@@ -188,9 +188,7 @@ static int display_remote;
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 const char* keyboard_layout = NULL;
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 ram_addr_t ram_size;
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 const char *mem_path = NULL;
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-#ifdef MAP_POPULATE
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 int mem_prealloc = 0; /* force preallocation of physical target memory */
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-#endif
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 int nb_nics;
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 NICInfo nd_table[MAX_NICS];
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 int autostart;
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@@ -3174,11 +3172,9 @@ int main(int argc, char **argv, char **envp)
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             case QEMU_OPTION_mempath:
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                 mem_path = optarg;
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                 break;
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-#ifdef MAP_POPULATE
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             case QEMU_OPTION_mem_prealloc:
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                 mem_prealloc = 1;
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                 break;
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-#endif
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             case QEMU_OPTION_d:
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                 log_mask = optarg;
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                 break;
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-- 
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1.7.11.7
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