linux-kernel - Re: [PATCH] KVM: ia64: remove

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Date:	Thu, 20 Nov 2014 14:38:10 +0100
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	linux-ia64@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH] KVM: ia64: remove

2014-11-19 22:05+0100, Paolo Bonzini:
> KVM for ia64 has been marked as broken not just once, but twice even,
> and the last patch from the maintainer is now roughly 5 years old.
> Time for it to rest in piece.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---

Nice, if only every diffstat was like that!

I propose another removal.
(The reasoning below wasn't confirmed with ia64 compiler.
 I'd remove the ioctls even if they worked.)

---8<---
KVM: remove buggy ia64 specific ioctls

IA64 is no longer present so new applications shouldn't use them.

The main problem is that they most likely didn't work even before,
because we have misused ioctl

  #define KVM_SET_GUEST_DEBUG       _IOW(KVMIO,  0x9b, struct kvm_guest_debug)
  #define KVM_IA64_VCPU_SET_STACK   _IOW(KVMIO,  0x9b, void *)

as

  struct kvm_guest_debug {
  	__u32 control;
  	__u32 pad;
  	struct kvm_guest_debug_arch arch;
  };

and

  struct kvm_guest_debug_arch {
  };

mean that

  sizeof(struct kvm_guest_debug) == sizeof(void *) == 8

thus

  KVM_SET_GUEST_DEBUG == KVM_IA64_VCPU_SET_STACK

and KVM_SET_GUEST_DEBUG is handled before KVM_IA64_VCPU_SET_STACK.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 include/uapi/linux/kvm.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6d59e5b..a37fd12 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1099,9 +1099,6 @@ struct kvm_s390_ucas_mapping {
 #define KVM_X86_SETUP_MCE         _IOW(KVMIO,  0x9c, __u64)
 #define KVM_X86_GET_MCE_CAP_SUPPORTED _IOR(KVMIO,  0x9d, __u64)
 #define KVM_X86_SET_MCE           _IOW(KVMIO,  0x9e, struct kvm_x86_mce)
-/* IA64 stack access */
-#define KVM_IA64_VCPU_GET_STACK   _IOR(KVMIO,  0x9a, void *)
-#define KVM_IA64_VCPU_SET_STACK   _IOW(KVMIO,  0x9b, void *)
 /* Available with KVM_CAP_VCPU_EVENTS */
 #define KVM_GET_VCPU_EVENTS       _IOR(KVMIO,  0x9f, struct kvm_vcpu_events)
 #define KVM_SET_VCPU_EVENTS       _IOW(KVMIO,  0xa0, struct kvm_vcpu_events)
-- 
2.1.0

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