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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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