On 05.05.2016 08:17, Paul Mackerras wrote:
> When the guest does a sign-extending load instruction (such as lha
> or lwa) to an emulated MMIO location, it results in a call to
> kvmppc_handle_loads() in the host. That function sets the
> vcpu->arch.mmio_sign_extend flag and calls kvmppc_handle_load()
> to do the rest of the work. However, kvmppc_handle_load() sets
> the mmio_sign_extend flag to 0 unconditionally, so the sign
> extension never gets done.
>
> To fix this, we rename kvmppc_handle_load to __kvmppc_handle_load
> and add an explicit parameter to indicate whether sign extension
> is required. kvmppc_handle_load() and kvmppc_handle_loads() then
> become 1-line functions that just call __kvmppc_handle_load()
> with the extra parameter.
>
> Reported-by: Bin Lu <lblulb@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
> ---
> arch/powerpc/kvm/powerpc.c | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 6a68730..02416fe 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -800,9 +800,9 @@ static void kvmppc_complete_mmio_load(struct kvm_vcpu *vcpu,
> }
> }
>
> -int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
> - unsigned int rt, unsigned int bytes,
> - int is_default_endian)
> +static int __kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
> + unsigned int rt, unsigned int bytes,
> + int is_default_endian, int sign_extend)
> {
> int idx, ret;
> bool host_swabbed;
> @@ -827,7 +827,7 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
> vcpu->arch.mmio_host_swabbed = host_swabbed;
> vcpu->mmio_needed = 1;
> vcpu->mmio_is_write = 0;
> - vcpu->arch.mmio_sign_extend = 0;
> + vcpu->arch.mmio_sign_extend = sign_extend;
>
> idx = srcu_read_lock(&vcpu->kvm->srcu);
>
> @@ -844,6 +844,13 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
>
> return EMULATE_DO_MMIO;
> }
> +
> +int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
> + unsigned int rt, unsigned int bytes,
> + int is_default_endian)
> +{
> + return __kvmppc_handle_load(run, vcpu, rt, bytes, is_default_endian, 0);
> +}
> EXPORT_SYMBOL_GPL(kvmppc_handle_load);
>
> /* Same as above, but sign extends */
> @@ -851,12 +858,7 @@ int kvmppc_handle_loads(struct kvm_run *run, struct kvm_vcpu *vcpu,
> unsigned int rt, unsigned int bytes,
> int is_default_endian)
> {
> - int r;
> -
> - vcpu->arch.mmio_sign_extend = 1;
> - r = kvmppc_handle_load(run, vcpu, rt, bytes, is_default_endian);
> -
> - return r;
> + return __kvmppc_handle_load(run, vcpu, rt, bytes, is_default_endian, 1);
> }
>
> int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
>
Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
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