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KVM: PPC: Add helpers to modify ppc fields 

The PowerPC specification always lists bits from MSB to LSB. That is
really confusing when you're trying to write C code, because it fits
in pretty badly with the normal (1 << xx) schemes.

So I came up with some nice wrappers that allow to get and set fields
in a u64 with bit numbers exactly as given in the spec. That makes the
code in KVM and the spec easier comparable.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Alexander Graf 2010-02-19 11:00:42 +01:00 committed by Avi Kivity
parent dba2e123e7
commit 0564ee8a86
1 changed files with 33 additions and 0 deletions
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33
arch/powerpc/include/asm/kvm_ppc.h
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@ -103,6 +103,39 @@ extern void kvmppc_booke_exit(void);
extern void kvmppc_core_destroy_mmu(struct kvm_vcpu *vcpu);
/*
* Cuts out inst bits with ordering according to spec.
* That means the leftmost bit is zero. All given bits are included.
*/
static inline u32 kvmppc_get_field(u64 inst, int msb, int lsb)
{
u32 r;
u32 mask;
BUG_ON(msb > lsb);
mask = (1 << (lsb - msb + 1)) - 1;
r = (inst >> (63 - lsb)) & mask;
return r;
}
/*
* Replaces inst bits with ordering according to spec.
*/
static inline u32 kvmppc_set_field(u64 inst, int msb, int lsb, int value)
{
u32 r;
u32 mask;
BUG_ON(msb > lsb);
mask = ((1 << (lsb - msb + 1)) - 1) << (63 - lsb);
r = (inst & ~mask) | ((value << (63 - lsb)) & mask);
return r;
}
#ifdef CONFIG_PPC_BOOK3S
/* We assume we're always acting on the current vcpu */