[PATCH 2/6] kvmppc: magic page hypercall - host part

[ehrhardt@linux.vnet.ibm.com]

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

This adds the host part of the magic page registration. This is a memory
area of the guest granted to the host.
The patch just introduces the infrastruture to receive and map the guest paddr.
This is later used storage area a guest can read unprivileged (using binary
rewriting to change privileges instructions).
The dtlb misses to the paravirtualized area are handled in the host to prevent
dead lock if those misses would occur in the dtlb miss handler. A new exit
counter in the ppc kvm stats cover this new exit type.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
---

[diffstat]
 arch/powerpc/kvm/booke_guest.c |   14 ++++++++++++++
 arch/powerpc/kvm/emulate.c     |   13 ++++++++++++-
 arch/powerpc/kvm/powerpc.c     |   19 ++++++++++++++++++-
 include/asm-powerpc/kvm_host.h |    6 ++++++
 include/asm-powerpc/kvm_para.h |   24 ++++++++++++++++++++++++
 include/linux/kvm.h            |    5 +++++
 6 files changed, 79 insertions(+), 2 deletions(-)

[diff]

diff --git a/arch/powerpc/kvm/booke_guest.c b/arch/powerpc/kvm/booke_guest.c
--- a/arch/powerpc/kvm/booke_guest.c
+++ b/arch/powerpc/kvm/booke_guest.c
@@ -21,6 +21,7 @@
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/kvm_host.h>
+#include <linux/kvm_para.h>
 #include <linux/module.h>
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
@@ -43,6 +44,7 @@
 	{ "itlb_v",     VCPU_STAT(itlb_virt_miss_exits) },
 	{ "dtlb_r",     VCPU_STAT(dtlb_real_miss_exits) },
 	{ "dtlb_v",     VCPU_STAT(dtlb_virt_miss_exits) },
+	{ "dtlb_pv",    VCPU_STAT(dtlb_pvmem_miss_exits) },
 	{ "sysc",       VCPU_STAT(syscall_exits) },
 	{ "isi",        VCPU_STAT(isi_exits) },
 	{ "dsi",        VCPU_STAT(dsi_exits) },
@@ -337,6 +339,16 @@
 		unsigned long eaddr = vcpu->arch.fault_dear;
 		gfn_t gfn;
 
+
+		if (vcpu->arch.pvmem && kvmppc_is_pvmem(vcpu, eaddr)) {
+			kvmppc_mmu_map(vcpu, eaddr,
+			 vcpu->arch.pvmem_gpaddr >> KVM_PPCPV_MAGIC_PAGE_SHIFT,
+			 0, KVM_PPCPV_MAGIC_PAGE_FLAGS);
+			vcpu->stat.dtlb_pvmem_miss_exits++;
+			r = RESUME_GUEST;
+			break;
+		}
+
 		/* Check the guest TLB. */
 		gtlbe = kvmppc_44x_dtlb_search(vcpu, eaddr);
 		if (!gtlbe) {
@@ -488,6 +500,8 @@
 
 	vcpu->arch.shadow_pid = 1;
 
+	vcpu->arch.pvmem = NULL;
+
 	/* Eye-catching number so we know if the guest takes an interrupt
 	 * before it's programmed its own IVPR. */
 	vcpu->arch.ivpr = 0x55550000;
diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
--- a/arch/powerpc/kvm/emulate.c
+++ b/arch/powerpc/kvm/emulate.c
@@ -21,6 +21,7 @@
 #include <linux/timer.h>
 #include <linux/types.h>
 #include <linux/string.h>
+#include <linux/highmem.h>
 #include <linux/kvm_host.h>
 #include <linux/kvm_para.h>
 
@@ -195,7 +196,7 @@
 		          get_jiffies_64() + nr_jiffies);
 	} else {
 		del_timer(&vcpu->arch.dec_timer);
-	}
+}
 }
 
 static void kvmppc_emul_rfi(struct kvm_vcpu *vcpu)
@@ -207,8 +208,18 @@
 static int kvmppc_do_hypercall(struct kvm_vcpu *vcpu)
 {
 	int ret = 0;
+	struct page *pvmem_page;
 
 	switch (vcpu->arch.gpr[0]) {
+	case KVM_HCALL_RESERVE_MAGICPAGE:
+		vcpu->arch.pvmem_gvaddr = vcpu->arch.gpr[3];
+		vcpu->arch.pvmem_gpaddr = vcpu->arch.gpr[4];
+		down_read(&current->mm->mmap_sem);
+		pvmem_page = gfn_to_page(vcpu->kvm, 
+			vcpu->arch.pvmem_gpaddr >> KVM_PPCPV_MAGIC_PAGE_SHIFT);
+		up_read(&current->mm->mmap_sem);
+		vcpu->arch.pvmem = kmap(pvmem_page);
+		break;
 	default:
 		printk(KERN_ERR "unknown hypercall %d\n", vcpu->arch.gpr[0]);
 		kvmppc_dump_vcpu(vcpu);
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -21,6 +21,7 @@
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/kvm_host.h>
+#include <linux/kvm_para.h>
 #include <linux/module.h>
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
@@ -148,6 +149,9 @@
 	case KVM_CAP_COALESCED_MMIO:
 		r = KVM_COALESCED_MMIO_PAGE_OFFSET;
 		break;
+	case KVM_CAP_PPCPV_MAGICPAGE:
+		r = 1;
+		break;
 	default:
 		r = 0;
 		break;
@@ -159,7 +163,20 @@
 long kvm_arch_dev_ioctl(struct file *filp,
                         unsigned int ioctl, unsigned long arg)
 {
-	return -EINVAL;
+	long r = -EINVAL;
+
+	switch (ioctl) {
+	case KVM_GET_PPCPV_MAGICPAGE_SIZE:
+		if (arg)
+			goto out;
+		r = KVM_PPCPV_MAGIC_PAGE_SIZE;
+		break;
+	default:
+		break;
+	}
+out:
+	return r;
+
 }
 
 int kvm_arch_set_memory_region(struct kvm *kvm,
diff --git a/include/asm-powerpc/kvm_host.h b/include/asm-powerpc/kvm_host.h
--- a/include/asm-powerpc/kvm_host.h
+++ b/include/asm-powerpc/kvm_host.h
@@ -54,6 +54,7 @@
 	u32 itlb_real_miss_exits;
 	u32 itlb_virt_miss_exits;
 	u32 dtlb_real_miss_exits;
+	u32 dtlb_pvmem_miss_exits;
 	u32 dtlb_virt_miss_exits;
 	u32 syscall_exits;
 	u32 isi_exits;
@@ -151,6 +152,11 @@
 
 	struct timer_list dec_timer;
 	unsigned long pending_exceptions;
+
+	/* guest paravirtualization helpers */
+	long unsigned int pvmem_gvaddr; /* guests address to pvmem to rewrite guest code */
+	long unsigned int pvmem_gpaddr; /* guests physical backing gor the pvmem */
+	void *pvmem;	  /* host mapping pvmem */
 };
 
 struct kvm_guest_debug {
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
@@ -22,7 +22,19 @@
 
 #ifdef __KERNEL__
 
+#include <linux/kvm_host.h>
+
 #define KVM_HYPERCALL_BIN 0x03ffffff
+
+#define KVM_HCALL_RESERVE_MAGICPAGE	0
+
+/* 
+ * the guest guarantees alignment to requested size, choosing page size here
+ * easens tlb handling which is handled by host for the magic page
+ */
+#define KVM_PPCPV_MAGIC_PAGE_SIZE 4096
+#define KVM_PPCPV_MAGIC_PAGE_SHIFT 12
+#define KVM_PPCPV_MAGIC_PAGE_FLAGS 0x3f
 
 static inline int kvm_para_available(void)
 {
@@ -34,6 +46,18 @@
 	return 0;
 }
 
+static inline int kvmppc_is_pvmem(struct kvm_vcpu *vcpu, unsigned long eaddr)
+{
+	return (vcpu->arch.pvmem &&
+		(eaddr >> KVM_PPCPV_MAGIC_PAGE_SHIFT) = 
+		(vcpu->arch.pvmem_gvaddr >> KVM_PPCPV_MAGIC_PAGE_SHIFT));
+}
+
+static inline int kvmppc_has_pvmem(struct kvm_vcpu *vcpu)
+{
+	return vcpu->arch.pvmem;
+}
+
 #endif /* __KERNEL__ */
 
 #endif /* __POWERPC_KVM_PARA_H__ */
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -365,6 +365,10 @@
 #define KVM_TRACE_PAUSE           _IO(KVMIO,  0x07)
 #define KVM_TRACE_DISABLE         _IO(KVMIO,  0x08)
 /*
+ * ioctls for powerpc paravirtualization extensions
+ */
+#define KVM_GET_PPCPV_MAGICPAGE_SIZE       _IO(KVMIO,   0x09)
+/*
  * Extension capability list.
  */
 #define KVM_CAP_IRQCHIP	  0
@@ -382,6 +386,7 @@
 #define KVM_CAP_PV_MMU 13
 #define KVM_CAP_MP_STATE 14
 #define KVM_CAP_COALESCED_MMIO 15
+#define KVM_CAP_PPCPV_MAGICPAGE 16
 
 /*
  * ioctls for VM fds