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    Subject[PATCH 3/6] KVM: x86: wean in-kernel PIO from vcpu->arch.pio*
    Date
    Make emulator_pio_in_out operate directly on the provided buffer
    as long as PIO is handled inside KVM.

    For input operations, this means that, in the case of in-kernel
    PIO, __emulator_pio_in does not have to be always followed
    by complete_emulator_pio_in. This affects emulator_pio_in and
    kvm_sev_es_ins; for the latter, that is why the call moves from
    advance_sev_es_emulated_ins to complete_sev_es_emulated_ins.

    For output, it means that vcpu->pio.count is never set unnecessarily
    and there is no need to clear it.

    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    ---
    arch/x86/kvm/x86.c | 61 ++++++++++++++++++++--------------------------
    1 file changed, 27 insertions(+), 34 deletions(-)

    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 8e1e76d0378b..3b641cd2ff6f 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -7423,16 +7423,6 @@ static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
    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;
    -
    for (i = 0; i < count; i++) {
    if (in)
    r = kvm_io_bus_read(vcpu, KVM_PIO_BUS, port, size, data);
    @@ -7446,6 +7436,16 @@ static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,

    userspace_io:
    WARN_ON(i != 0);
    + 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);
    +
    vcpu->run->exit_reason = KVM_EXIT_IO;
    vcpu->run->io.direction = in ? KVM_EXIT_IO_IN : KVM_EXIT_IO_OUT;
    vcpu->run->io.size = size;
    @@ -7457,9 +7457,13 @@ 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)
    + unsigned short port, void *val, unsigned int count)
    {
    - return emulator_pio_in_out(vcpu, size, port, NULL, count, true);
    + int r = emulator_pio_in_out(vcpu, size, port, val, count, true);
    + if (r)
    + trace_kvm_pio(KVM_PIO_IN, port, size, count, val);
    +
    + return r;
    }

    static void complete_emulator_pio_in(struct kvm_vcpu *vcpu, void *val)
    @@ -7482,16 +7486,11 @@ static int emulator_pio_in(struct kvm_vcpu *vcpu, int size,
    * shenanigans as KVM doesn't support modifying the rep count,
    * and the emulator ensures @count doesn't overflow the buffer.
    */
    + complete_emulator_pio_in(vcpu, val);
    + return 1;
    } else {
    - int r = __emulator_pio_in(vcpu, size, port, count);
    - if (!r)
    - return r;
    -
    - /* Results already available, fall through. */
    + return __emulator_pio_in(vcpu, size, port, val, count);
    }
    -
    - complete_emulator_pio_in(vcpu, val);
    - return 1;
    }

    static int emulator_pio_in_emulated(struct x86_emulate_ctxt *ctxt,
    @@ -7506,14 +7505,8 @@ static int emulator_pio_out(struct kvm_vcpu *vcpu, int size,
    unsigned short port, const void *val,
    unsigned int count)
    {
    - int ret;
    -
    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;
    -
    - return ret;
    + return emulator_pio_in_out(vcpu, size, port, (void *)val, count, false);
    }

    static int emulator_pio_out_emulated(struct x86_emulate_ctxt *ctxt,
    @@ -13064,20 +13057,20 @@ static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
    static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size,
    unsigned int port);

    -static void advance_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
    +static void advance_sev_es_emulated_ins(struct kvm_vcpu *vcpu, unsigned count, int size)
    {
    - unsigned count = vcpu->arch.pio.count;
    - complete_emulator_pio_in(vcpu, vcpu->arch.sev_pio_data);
    vcpu->arch.sev_pio_count -= count;
    - vcpu->arch.sev_pio_data += count * vcpu->arch.pio.size;
    + vcpu->arch.sev_pio_data += count * size;
    }

    static int complete_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
    {
    + unsigned count = vcpu->arch.pio.count;
    int size = vcpu->arch.pio.size;
    int port = vcpu->arch.pio.port;

    - advance_sev_es_emulated_ins(vcpu);
    + complete_emulator_pio_in(vcpu, vcpu->arch.sev_pio_data);
    + advance_sev_es_emulated_ins(vcpu, count, size);
    if (vcpu->arch.sev_pio_count)
    return kvm_sev_es_ins(vcpu, size, port);
    return 1;
    @@ -13089,11 +13082,11 @@ static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size,
    for (;;) {
    unsigned int count =
    min_t(unsigned int, PAGE_SIZE / size, vcpu->arch.sev_pio_count);
    - if (!__emulator_pio_in(vcpu, size, port, count))
    + if (!__emulator_pio_in(vcpu, size, port, vcpu->arch.sev_pio_data, count))
    break;

    /* Emulation done by the kernel. */
    - advance_sev_es_emulated_ins(vcpu);
    + advance_sev_es_emulated_ins(vcpu, count, size);
    if (!vcpu->arch.sev_pio_count)
    return 1;
    }
    --
    2.31.1

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