On Wed, Jun 08, 2022, Paolo Bonzini wrote:
> For now, this is basically an excuse to add back the void* argument to
> the function, while removing some knowledge of vcpu->arch.pio* from
> its callers. The WARN that vcpu->arch.pio.count is zero is also
> extended to OUT operations.
>
> We cannot do more as long as we have __emulator_pio_in always followed
Please add parantheses when referencing functions in shortlogs and changelogs,
I find it tremendously helpful.
> by complete_emulator_pio_in, which uses the vcpu->arch.pio* fields.
> But after fixing that, it will be possible to only populate the
> vcpu->arch.pio* fields on userspace exits.
Same nits about about pronouns. In a similar vein, be explicit about what "more"
mean; I had no idea what "more" meant until the second sentence. E.g.
The vcpu->arch.pio* fields still need to be filled even when the PIO is
handled in-kernel as __emulator_pio_in() is always followed by
complete_emulator_pio_in(). But after fixing that, it will be possible to
to only populate the vcpu->arch.pio* fields on userspace exits.
> No functional change intended.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/trace.h | 2 +-
> arch/x86/kvm/x86.c | 18 ++++++++++--------
> 2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index fd28dd40b813..2877c0e92823 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -154,7 +154,7 @@ TRACE_EVENT(kvm_xen_hypercall,
>
> TRACE_EVENT(kvm_pio,
> TP_PROTO(unsigned int rw, unsigned int port, unsigned int size,
> - unsigned int count, void *data),
> + unsigned int count, const void *data),
> TP_ARGS(rw, port, size, count, data),
>
> TP_STRUCT__entry(
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2f9100f2564e..8e1e76d0378b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7416,17 +7416,22 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> }
>
> static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
> - unsigned short port,
> + unsigned short port, void *data,
> unsigned int count, bool in)
> {
> - void *data = vcpu->arch.pio_data;
> unsigned i;
> int r;
>
> + WARN_ON_ONCE(vcpu->arch.pio.count);
> vcpu->arch.pio.port = port;
> vcpu->arch.pio.in = in;
> vcpu->arch.pio.count = count;
> vcpu->arch.pio.size = size;
> + if (in)
> + memset(vcpu->arch.pio_data, 0, size * count);
> + else
> + memcpy(vcpu->arch.pio_data, data, size * count);
> + data = vcpu->arch.pio_data;
Oof, passing NULL for @data and then overwriting it below is gross. It also makes
@in redundant for this one patch. Might be worth adding a comment, even though
it's transient?
>
> for (i = 0; i < count; i++) {
> if (in)
> @@ -7454,9 +7459,7 @@ static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
> static int __emulator_pio_in(struct kvm_vcpu *vcpu, int size,
> unsigned short port, unsigned int count)
> {
> - WARN_ON(vcpu->arch.pio.count);
> - memset(vcpu->arch.pio_data, 0, size * count);
> - return emulator_pio_in_out(vcpu, size, port, count, true);
> + return emulator_pio_in_out(vcpu, size, port, NULL, count, true);
> }
>
> static void complete_emulator_pio_in(struct kvm_vcpu *vcpu, void *val)
> @@ -7505,9 +7508,8 @@ static int emulator_pio_out(struct kvm_vcpu *vcpu, int size,
> {
> int ret;
>
> - memcpy(vcpu->arch.pio_data, val, size * count);
> - trace_kvm_pio(KVM_PIO_OUT, port, size, count, vcpu->arch.pio_data);
> - ret = emulator_pio_in_out(vcpu, size, port, count, false);
> + trace_kvm_pio(KVM_PIO_OUT, port, size, count, val);
> + ret = emulator_pio_in_out(vcpu, size, port, (void *)val, count, false);
> if (ret)
> vcpu->arch.pio.count = 0;
>
> --
> 2.31.1
>
>
