From: Christian Ehrhardt <[EMAIL PROTECTED]>
This patch adds the guest handling for the magic page mechanism. A Hypervisor
can modify the device tree passed to the guest. Using that already existing
interface a guest can simply detect available hypervisor features and agree
on the supported ones using hypercalls.
In this example it is checked for the feature switch "feature,pv-magicpage"
in the hypervisor node and additional data which represents the size the
hypervisor requests in "data,pv-magicpage-size".
When the guest read that data and wants to support it the memory is allocated
and passed to the hypervisor using the KVM_HCALL_RESERVE_MAGICPAGE hypercall.
Signed-off-by: Christian Ehrhardt <[EMAIL PROTECTED]>
---
[diffstat]
arch/powerpc/kernel/kvm.c | 48 +++++++++++++++++++++++++++++++++++++++++
include/asm-powerpc/kvm_para.h | 27 ++++++++++++++++++++++-
2 files changed, 74 insertions(+), 1 deletion(-)
[diff]
diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
--- a/arch/powerpc/kernel/kvm.c
+++ b/arch/powerpc/kernel/kvm.c
@@ -22,9 +22,57 @@
#include <linux/percpu.h>
#include <linux/mm.h>
#include <linux/kvm_para.h>
+#include <linux/bootmem.h>
+
+/*
+ * this is guest memory granted to the hypervisor;
+ * the hypervisor can place data in this area and rewrite
+ * privileged instructions to read from this area without
+ * trapping.
+ * Only the Hypervisor needs to be aware of the structure layout
+ * which makes the guest more felxible - the guest only guarantees
+ * the size which is requested by the hypervisor and read from a
+ * device tree entry.
+ */
+void *kvm_magicpage;
+
+static void __init kvmppc_register_magic_page(void)
+{
+ unsigned long paddr;
+ int size;
+ long err;
+
+ size = kvmppc_pv_read_data(KVM_PVDATA_MAGICPAGE_SIZE);
+ if (size < 0) {
+ printk(KERN_ERR"%s: couldn't read size for kvmppc style "
+ "paravirtualization support (got %d)\n",
+ __func__, size);
+ return;
+ }
+
+ /* FIXME Guest SMP needs that percpu
+ * On SMP we might also need a free implementation */
+ kvm_magicpage = alloc_bootmem(size);
+ if (!kvm_magicpage) {
+ printk(KERN_ERR"%s - failed to allocate %d bytes\n",
+ __func__, size);
+ return;
+ }
+
+ paddr = (unsigned long)__pa(kvm_magicpage);
+ err = kvm_hypercall1(KVM_HCALL_RESERVE_MAGICPAGE, paddr);
+ if (err)
+ printk(KERN_ERR"%s: couldn't register magic page\n", __func__);
+ else
+ printk(KERN_NOTICE"%s: registered %d bytes for "
+ "virtualization support\n", __func__, size);
+}
void __init kvm_guest_init(void)
{
if (!kvm_para_available())
return;
+
+ if (kvm_para_has_feature(KVM_FEATURE_PPCPV_MAGICPAGE))
+ kvmppc_register_magic_page();
}
diff --git a/include/asm-powerpc/kvm_para.h b/include/asm-powerpc/kvm_para.h
--- a/include/asm-powerpc/kvm_para.h
+++ b/include/asm-powerpc/kvm_para.h
@@ -28,10 +28,18 @@
#define KVM_HYPERCALL_BIN 0x03ffffff
+#define KVM_HCALL_RESERVE_MAGICPAGE 0
+
+#define KVM_PVDATA_MAGICPAGE_SIZE "data,pv-magicpage-size"
+
+/* List of PV features supported, returned as a bitfield */
+#define KVM_FEATURE_PPCPV_MAGICPAGE 0
+
static struct kvmppc_para_features {
char *dtcell;
int feature;
} para_features[] = {
+ { "feature,pv-magicpage", KVM_FEATURE_PPCPV_MAGICPAGE }
};
static inline int kvm_para_available(void)
@@ -54,13 +62,30 @@
if (!dn)
return 0;
- for (i = 0; i < ARRAY_SIZE(para_features)-1; i++) {
+ for (i = 0; i < ARRAY_SIZE(para_features); i++) {
dtval = of_get_property(dn, para_features[i].dtcell, NULL);
if (dtval && *dtval == 1)
features |= (1 << para_features[i].feature);
}
return features;
+}
+
+/* reads the specified data field out of the hypervisor node */
+static inline int kvmppc_pv_read_data(char *dtcell)
+{
+ struct device_node *dn;
+ const int *dtval;
+
+ dn = of_find_node_by_path("/hypervisor");
+ if (!dn)
+ return -EINVAL;
+
+ dtval = of_get_property(dn, dtcell, NULL);
+ if (dtval)
+ return *dtval;
+ else
+ return -EINVAL;
}
void kvm_guest_init(void);
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