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Blame SOURCES/kvm-s390x-Enable-KVM-huge-page-backing-support.patch

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From c9ff4b704e6be10e4309b5cdb8c2d3e7fc0d3d0f Mon Sep 17 00:00:00 2001
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From: David Hildenbrand <david@redhat.com>
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Date: Mon, 6 Aug 2018 14:18:41 +0100
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Subject: [PATCH 2/3] s390x: Enable KVM huge page backing support
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RH-Author: David Hildenbrand <david@redhat.com>
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Message-id: <20180806141842.23963-3-david@redhat.com>
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Patchwork-id: 81645
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O-Subject: [RHEL-8.0 qemu-kvm PATCH v2 2/3] s390x: Enable KVM huge page backing support
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Bugzilla: 1610906
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1610906
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Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=17624600
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Upstream: N/A
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Kernel part is in kvm/next, scheduled for 4.19. Patch has been reviewed
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upstream but cannot get picked up yet due to the outstanding linux
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header sync. Conflict to upstream patch: We have no units.h, therefore
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we have to unfold "4*KiB" and "1*MiB".
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QEMU has had huge page support for a longer time already, but KVM
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memory management under s390x needed some changes to work with huge
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backings.
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Now that we have support, let's enable it if requested and
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available. Otherwise we now properly tell the user if there is no
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support and back out instead of failing to run the VM later on.
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Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
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Reviewed-by: David Hildenbrand <david@redhat.com>
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Signed-off-by: David Hildenbrand <david@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 target/s390x/kvm.c | 34 ++++++++++++++++++++++++++++++++--
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 1 file changed, 32 insertions(+), 2 deletions(-)
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diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
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index fbccceb..3474310a9 100644
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--- a/target/s390x/kvm.c
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+++ b/target/s390x/kvm.c
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@@ -34,6 +34,7 @@
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 #include "qapi/error.h"
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 #include "qemu/error-report.h"
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 #include "qemu/timer.h"
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+#include "qemu/mmap-alloc.h"
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 #include "sysemu/sysemu.h"
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 #include "sysemu/hw_accel.h"
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 #include "hw/hw.h"
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@@ -140,6 +141,7 @@ static int cap_mem_op;
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 static int cap_s390_irq;
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 static int cap_ri;
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 static int cap_gs;
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+static int cap_hpage_1m;
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 static int active_cmma;
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@@ -221,9 +223,9 @@ static void kvm_s390_enable_cmma(void)
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         .attr = KVM_S390_VM_MEM_ENABLE_CMMA,
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     };
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-    if (mem_path) {
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+    if (cap_hpage_1m) {
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         warn_report("CMM will not be enabled because it is not "
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-                    "compatible with hugetlbfs.");
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+                    "compatible with huge memory backings.");
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         return;
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     }
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     rc = kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attr);
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@@ -282,10 +284,38 @@ void kvm_s390_crypto_reset(void)
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     }
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 }
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+static int kvm_s390_configure_mempath_backing(KVMState *s)
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+{
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+    size_t path_psize = qemu_mempath_getpagesize(mem_path);
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+
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+    if (path_psize == 4 * 1024) {
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+        return 0;
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+    }
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+
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+    if (path_psize != 1024 * 1024) {
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+        error_report("Memory backing with 2G pages was specified, "
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+                     "but KVM does not support this memory backing");
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+        return -EINVAL;
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+    }
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+
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+    if (kvm_vm_enable_cap(s, KVM_CAP_S390_HPAGE_1M, 0)) {
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+        error_report("Memory backing with 1M pages was specified, "
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+                     "but KVM does not support this memory backing");
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+        return -EINVAL;
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+    }
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+
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+    cap_hpage_1m = 1;
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+    return 0;
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+}
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+
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 int kvm_arch_init(MachineState *ms, KVMState *s)
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 {
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     MachineClass *mc = MACHINE_GET_CLASS(ms);
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+    if (mem_path && kvm_s390_configure_mempath_backing(s)) {
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+        return -EINVAL;
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+    }
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+
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     mc->default_cpu_type = S390_CPU_TYPE_NAME("host");
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     cap_sync_regs = kvm_check_extension(s, KVM_CAP_SYNC_REGS);
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     cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
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-- 
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1.8.3.1
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