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 reads 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 | 51 +++++++++++++++++++++++++++++++++++++++++
include/asm-powerpc/fixmap.h | 10 +++++++-
include/asm-powerpc/kvm_para.h | 26 ++++++++++++++++++++
mm/page_alloc.c | 1
4 files changed, 87 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 +22,60 @@
#include <linux/percpu.h>
#include <linux/mm.h>
#include <linux/kvm_para.h>
+#include <linux/bootmem.h>
+#include <asm/fixmap.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.
+ */
+static void *kvm_magicpage;
+
+static void __init kvmppc_register_magic_page(void)
+{
+ unsigned long gvaddr;
+ unsigned long gpaddr;
+ 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 which */
+ kvm_magicpage = alloc_bootmem(size);
+ if (!kvm_magicpage) {
+ printk(KERN_ERR "%s - failed to allocate %d bytes\n",
+ __func__, size);
+ return;
+ }
+ gpaddr = (unsigned long)__pa(kvm_magicpage);
+ gvaddr = fix_to_virt(FIX_KVM_PV);
+
+ err = kvm_hypercall2(KVM_HCALL_RESERVE_MAGICPAGE, gvaddr, gpaddr);
+ if (err)
+ printk(KERN_ERR "%s: couldn't register pv mem\n", __func__);
+ else
+ printk(KERN_NOTICE "%s: registered %d bytes for pv mem support"
+ " (gvaddr 0x%08lx gpaddr 0x%08lx)\n",
+ __func__, size, gvaddr, gpaddr);
+}
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/fixmap.h b/include/asm-powerpc/fixmap.h
--- a/include/asm-powerpc/fixmap.h
+++ b/include/asm-powerpc/fixmap.h
@@ -36,7 +36,7 @@
*
* these 'compile-time allocated' memory buffers are
* fixed-size 4k pages. (or larger if used with an increment
- * highger than 1) use fixmap_set(idx,phys) to associate
+ * higher than 1) use fixmap_set(idx,phys) to associate
* physical memory with fixmap indices.
*
* TLB entries of such buffers will not be flushed across
@@ -44,6 +44,14 @@
*/
enum fixed_addresses {
FIX_HOLE,
+#ifdef CONFIG_KVM_GUEST
+ /*
+ * reserved virtual address space for paravirtualization - needs to be
+ * <=32k away from base address 0 to be able to reach it with
+ * immediate addressing using base 0 instead of needing a register.
+ */
+ FIX_KVM_PV,
+#endif
#ifdef CONFIG_HIGHMEM
FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
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)
@@ -67,6 +75,24 @@
of_node_put(dn);
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);
+ of_node_put(dn);
+ if (dtval)
+ return *dtval;
+ else
+ return -EINVAL;
}
void kvm_guest_init(void);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -550,6 +550,7 @@
prefetchw(p + 1);
__ClearPageReserved(p);
set_page_count(p, 0);
+
}
set_page_refcounted(page);
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