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Message-ID: <fe3859c3b82f9bdf725e1c42fb270f3898bc86b5.camel@redhat.com>
Date: Tue, 26 Oct 2021 16:56:30 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: seanjc@...gle.com
Subject: Re: [PATCH 10/13] KVM: x86: wean in-kernel PIO from vcpu->arch.pio*
On Fri, 2021-10-22 at 11:36 -0400, Paolo Bonzini wrote:
> 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@...hat.com>
> ---
> arch/x86/kvm/x86.c | 63 +++++++++++++++++++++-------------------------
> 1 file changed, 28 insertions(+), 35 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 7c421d9fbcb6..e3d3c13fe803 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6894,16 +6894,6 @@ 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);
> @@ -6917,6 +6907,16 @@ 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;
> @@ -6928,9 +6928,13 @@ 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);
I have an idea to move the tracepoints that happen before userspace exit (this
one when we have in-kernel emulation, and one in emulator_pio_out to emulator_pio_in_out.
> +
> + return r;
> }
>
> static void complete_emulator_pio_in(struct kvm_vcpu *vcpu, void *val)
> @@ -6947,17 +6951,12 @@ static int emulator_pio_in(struct kvm_vcpu *vcpu, int size,
> {
> if (vcpu->arch.pio.count) {
> /* Complete previous iteration. */
> + WARN_ON(count != vcpu->arch.pio.count);
> + 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);
> }
> -
> - WARN_ON(count != vcpu->arch.pio.count);
> - complete_emulator_pio_in(vcpu, val);
> - return 1;
> }
>
> static int emulator_pio_in_emulated(struct x86_emulate_ctxt *ctxt,
> @@ -6972,14 +6971,8 @@ 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,
> @@ -12422,20 +12415,20 @@ 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;
> @@ -12447,11 +12440,11 @@ 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;
> }
Looks good, was a bit difficult to follow, so I might have missed something.
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
Best regards,
Maxim Levitsky
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