Re: [PATCH 18/26] KVM: PPC: KVM PV guest stubs

On 28.06.2010, at 06:39, Matt Evans wrote:

Howdy Alex!
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Alexander Graf wrote:

quoted

We will soon start and replace instructions from the text section =

with

quoted

other, paravirtualized versions. To ease the readability of those =

patches

quoted

I split out the generic looping and magic page mapping code out.
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This patch still only contains stubs. But at least it loops through =

the

quoted

text section :).
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Signed-off-by: Alexander Graf <redacted>
---
arch/powerpc/kernel/kvm.c |   59 =

+++++++++++++++++++++++++++++++++++++++++++++

quoted

1 files changed, 59 insertions(+), 0 deletions(-)
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diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
index 2d8dd73..d873bc6 100644
--- a/arch/powerpc/kernel/kvm.c
+++ b/arch/powerpc/kernel/kvm.c

@@ -32,3 +32,62 @@

#define KVM_MAGIC_PAGE		(-4096L)
#define magic_var(x) KVM_MAGIC_PAGE + offsetof(struct =

kvm_vcpu_arch_shared, x)

quoted

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+static bool kvm_patching_worked =3D true;
+
+static void kvm_map_magic_page(void *data)
+{
+	kvm_hypercall2(KVM_HC_PPC_MAP_MAGIC_PAGE,
+		       KVM_MAGIC_PAGE,  /* Physical Address */
+		       KVM_MAGIC_PAGE); /* Effective Address */
+}
+
+static void kvm_check_ins(u32 *inst)
+{
+	u32 _inst =3D *inst;
+	u32 inst_no_rt =3D _inst & ~KVM_MASK_RT;
+	u32 inst_rt =3D _inst & KVM_MASK_RT;
+
+	switch (inst_no_rt) {
+	}
+
+	switch (_inst) {
+	}
+
+	flush_icache_range((ulong)inst, (ulong)inst + 4);
+}
+
+static void kvm_use_magic_page(void)
+{
+	u32 *p;
+	u32 *start, *end;
+
+	/* Tell the host to map the magic page to -4096 on all CPUs */
+
+	on_each_cpu(kvm_map_magic_page, NULL, 1);
+
+	/* Now loop through all code and find instructions */
+
+	start =3D (void*)_stext;
+	end =3D (void*)_etext;
+
+	for (p =3D start; p < end; p++)
+		kvm_check_ins(p);
+}

=20
Could you do something similar in module_finalize() to patch loaded =

modules' .text sections?

I could, but do we need it? I objdump -d | grep'ed all my modules and =
didn't find any need to do so.


Alex