KVM: PPC: Book3S: Fix LPCR one_reg interface
Unfortunately, the LPCR got defined as a 32-bit register in the
one_reg interface. This is unfortunate because KVM allows userspace
to control the DPFD (default prefetch depth) field, which is in the
upper 32 bits. The result is that DPFD always get set to 0, which
reduces performance in the guest.
We can't just change KVM_REG_PPC_LPCR to be a 64-bit register ID,
since that would break existing userspace binaries. Instead we define
a new KVM_REG_PPC_LPCR_64 id which is 64-bit. Userspace can still use
the old KVM_REG_PPC_LPCR id, but it now only modifies those fields in
the bottom 32 bits that userspace can modify (ILE, TC and AIL).
If userspace uses the new KVM_REG_PPC_LPCR_64 id, it can modify DPFD
as well.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 6955318..884f819 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1869,7 +1869,8 @@
PPC | KVM_REG_PPC_PID | 64
PPC | KVM_REG_PPC_ACOP | 64
PPC | KVM_REG_PPC_VRSAVE | 32
- PPC | KVM_REG_PPC_LPCR | 64
+ PPC | KVM_REG_PPC_LPCR | 32
+ PPC | KVM_REG_PPC_LPCR_64 | 64
PPC | KVM_REG_PPC_PPR | 64
PPC | KVM_REG_PPC_ARCH_COMPAT 32
PPC | KVM_REG_PPC_DABRX | 32
diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
index 0e56d9e..e0e49db 100644
--- a/arch/powerpc/include/uapi/asm/kvm.h
+++ b/arch/powerpc/include/uapi/asm/kvm.h
@@ -548,6 +548,7 @@
#define KVM_REG_PPC_VRSAVE (KVM_REG_PPC | KVM_REG_SIZE_U32 | 0xb4)
#define KVM_REG_PPC_LPCR (KVM_REG_PPC | KVM_REG_SIZE_U32 | 0xb5)
+#define KVM_REG_PPC_LPCR_64 (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0xb5)
#define KVM_REG_PPC_PPR (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0xb6)
/* Architecture compatibility level */
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index f1281c4..0c5266e 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -863,7 +863,8 @@
return 0;
}
-static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr)
+static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
+ bool preserve_top32)
{
struct kvmppc_vcore *vc = vcpu->arch.vcore;
u64 mask;
@@ -898,6 +899,10 @@
mask = LPCR_DPFD | LPCR_ILE | LPCR_TC;
if (cpu_has_feature(CPU_FTR_ARCH_207S))
mask |= LPCR_AIL;
+
+ /* Broken 32-bit version of LPCR must not clear top bits */
+ if (preserve_top32)
+ mask &= 0xFFFFFFFF;
vc->lpcr = (vc->lpcr & ~mask) | (new_lpcr & mask);
spin_unlock(&vc->lock);
}
@@ -1011,6 +1016,7 @@
*val = get_reg_val(id, vcpu->arch.vcore->tb_offset);
break;
case KVM_REG_PPC_LPCR:
+ case KVM_REG_PPC_LPCR_64:
*val = get_reg_val(id, vcpu->arch.vcore->lpcr);
break;
case KVM_REG_PPC_PPR:
@@ -1216,7 +1222,10 @@
ALIGN(set_reg_val(id, *val), 1UL << 24);
break;
case KVM_REG_PPC_LPCR:
- kvmppc_set_lpcr(vcpu, set_reg_val(id, *val));
+ kvmppc_set_lpcr(vcpu, set_reg_val(id, *val), true);
+ break;
+ case KVM_REG_PPC_LPCR_64:
+ kvmppc_set_lpcr(vcpu, set_reg_val(id, *val), false);
break;
case KVM_REG_PPC_PPR:
vcpu->arch.ppr = set_reg_val(id, *val);
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index b18f2d4..e7a1fa2 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -1314,6 +1314,7 @@
*val = get_reg_val(id, to_book3s(vcpu)->hior);
break;
case KVM_REG_PPC_LPCR:
+ case KVM_REG_PPC_LPCR_64:
/*
* We are only interested in the LPCR_ILE bit
*/
@@ -1349,6 +1350,7 @@
to_book3s(vcpu)->hior_explicit = true;
break;
case KVM_REG_PPC_LPCR:
+ case KVM_REG_PPC_LPCR_64:
kvmppc_set_lpcr_pr(vcpu, set_reg_val(id, *val));
break;
default: