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[Qemu-devel] [PATCH 1/2] spapr: Fix stale HTAB during live migration (KV
From: |
Samuel Mendoza-Jonas |
Subject: |
[Qemu-devel] [PATCH 1/2] spapr: Fix stale HTAB during live migration (KVM) |
Date: |
Wed, 5 Nov 2014 17:17:00 +1100 |
If a guest reboots during a running migration, changes to the
hash page table are not necessarily updated on the destination.
Opening a new file descriptor to the HTAB forces the migration
handler to resend the entire table.
Signed-off-by: Samuel Mendoza-Jonas <address@hidden>
---
hw/ppc/spapr.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
include/hw/ppc/spapr.h | 2 ++
2 files changed, 49 insertions(+)
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 0a2bfe6..1610c28 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -833,6 +833,13 @@ static void spapr_reset_htab(sPAPREnvironment *spapr)
/* Kernel handles htab, we don't need to allocate one */
spapr->htab_shift = shift;
kvmppc_kern_htab = true;
+
+ /* Tell readers to update their file descriptor */
+ pthread_mutex_lock(&spapr->htab_mutex);
+ if (spapr->htab_fd > 0) {
+ spapr->htab_fd_stale = true;
+ }
+ pthread_mutex_unlock(&spapr->htab_mutex);
} else {
if (!spapr->htab) {
/* Allocate an htab if we don't yet have one */
@@ -850,6 +857,31 @@ static void spapr_reset_htab(sPAPREnvironment *spapr)
}
}
+/* A guest reset will cause spapr->htab_fd to become stale if being used.
+ * Reopen the file descriptor to make sure the whole HTAB is properly read.
+ */
+static int spapr_check_htab_fd(sPAPREnvironment *spapr)
+{
+ int rc = 0;
+
+ pthread_mutex_lock(&spapr->htab_mutex);
+
+ if (spapr->htab_fd_stale) {
+ close(spapr->htab_fd);
+ spapr->htab_fd = kvmppc_get_htab_fd(false);
+ if (spapr->htab_fd < 0) {
+ error_report("Unable to open fd for reading hash table from KVM: "
+ "%s", strerror(errno));
+ rc = -1;
+ }
+ spapr->htab_fd_stale = false;
+ }
+
+ pthread_mutex_unlock(&spapr->htab_mutex);
+ return rc;
+}
+
+
static void ppc_spapr_reset(void)
{
PowerPCCPU *first_ppc_cpu;
@@ -984,7 +1016,10 @@ static int htab_save_setup(QEMUFile *f, void *opaque)
} else {
assert(kvm_enabled());
+ pthread_mutex_lock(&spapr->htab_mutex);
spapr->htab_fd = kvmppc_get_htab_fd(false);
+ spapr->htab_fd_stale = false;
+ pthread_mutex_unlock(&spapr->htab_mutex);
if (spapr->htab_fd < 0) {
fprintf(stderr, "Unable to open fd for reading hash table from
KVM: %s\n",
strerror(errno));
@@ -1137,6 +1172,11 @@ static int htab_save_iterate(QEMUFile *f, void *opaque)
if (!spapr->htab) {
assert(kvm_enabled());
+ rc = spapr_check_htab_fd(spapr);
+ if (rc < 0) {
+ return rc;
+ }
+
rc = kvmppc_save_htab(f, spapr->htab_fd,
MAX_KVM_BUF_SIZE, MAX_ITERATION_NS);
if (rc < 0) {
@@ -1168,6 +1208,11 @@ static int htab_save_complete(QEMUFile *f, void *opaque)
assert(kvm_enabled());
+ rc = spapr_check_htab_fd(spapr);
+ if (rc < 0) {
+ return rc;
+ }
+
rc = kvmppc_save_htab(f, spapr->htab_fd, MAX_KVM_BUF_SIZE, -1);
if (rc < 0) {
return rc;
@@ -1355,6 +1400,8 @@ static void ppc_spapr_init(MachineState *machine)
spapr->htab_shift++;
}
+ pthread_mutex_init(&spapr->htab_mutex, NULL);
+
/* Set up Interrupt Controller before we create the VCPUs */
spapr->icp = xics_system_init(smp_cpus * kvmppc_smt_threads() /
smp_threads,
XICS_IRQS);
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 749daf4..5e29bec 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -37,6 +37,8 @@ typedef struct sPAPREnvironment {
int htab_save_index;
bool htab_first_pass;
int htab_fd;
+ bool htab_fd_stale;
+ pthread_mutex_t htab_mutex;
} sPAPREnvironment;
#define H_SUCCESS 0
--
1.9.3