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

Alexander Graf
2010-06-28T06:33:09Z

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

> Howdy Alex!
>
> Alexander Graf wrote:
>> We will soon start and replace instructions from the text section with
>> other, paravirtualized versions. To ease the readability of those patches
>> I split out the generic looping and magic page mapping code out.
>>
>> This patch still only contains stubs. But at least it loops through the
>> text section :).
>>
>> Signed-off-by: Alexander Graf <agraf-l3A5Bk7waGM@public.gmane.org>
>> ---
>> arch/powerpc/kernel/kvm.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
>> 1 files changed, 59 insertions(+), 0 deletions(-)
>>
>> 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)
>>
>> +static bool kvm_patching_worked = 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 = *inst;
>> + u32 inst_no_rt = _inst & ~KVM_MASK_RT;
>> + u32 inst_rt = _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 = (void*)_stext;
>> + end = (void*)_etext;
>> +
>> + for (p = start; p < end; p++)
>> + kvm_check_ins(p);
>> +}
>
> 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