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MIPS: KVM: Dynamically choose scratch registers

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Scratch cop0 registers are needed by KVM to be able to save/restore all
the GPRs, including k0/k1, and for storing the VCPU pointer. However no
registers are universally suitable for these purposes, so the decision
should be made at runtime.

Until now, we've used DDATA_LO to store the VCPU pointer, and ErrorEPC
as a temporary. It could be argued that this is abuse of those
registers, and DDATA_LO is known not to be usable on certain
implementations (Cavium Octeon). If KScratch registers are present, use
them instead.

We save & restore the temporary register in addition to the VCPU pointer
register when using a KScratch register for it, as it may be used for
normal host TLB handling too.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim KrÄmář <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
James Hogan
2016-06-23 17:34:45 +01:00
committed by Paolo Bonzini
parent 025014e3fb
commit 1e5217f542
3 changed files with 84 additions and 15 deletions
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4
arch/mips/kvm/mips.c
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@@ -1775,6 +1775,10 @@ static int __init kvm_mips_init(void)
{
int ret;
ret = kvm_mips_entry_setup();
if (ret)
return ret;
ret = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
if (ret)