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KVM: x86: wean in-kernel PIO from vcpu->arch.pio*

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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; but also vcpu->pio.size must not
be used in kvm_sev_es_outs(), because it will not be updated for
in-kernel OUT.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2022-06-15 10:24:01 -04:00
parent 30d583fd4e
commit 0c05e10bce
1 changed files with 32 additions and 41 deletions
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73
arch/x86/kvm/x86.c
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@ -7583,19 +7583,6 @@ 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) {
/* The buffer is only used in complete_emulator_pio_in(). */
WARN_ON(data);
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);
@ -7608,9 +7595,10 @@ static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
/*
* Userspace must have unregistered the device while PIO
* was running. Drop writes / read as 0 (the buffer
* was zeroed in __emulator_pio_in).
* was running. Drop writes / read as 0.
*/
if (in)
memset(data, 0, size * (count - i));
break;
}
@ -7619,6 +7607,16 @@ static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
return 1;
userspace_io:
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;
@ -7629,15 +7627,19 @@ userspace_io:
}
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)
{
int size = vcpu->arch.pio.size;
unsigned count = vcpu->arch.pio.count;
unsigned int count = vcpu->arch.pio.count;
memcpy(val, vcpu->arch.pio_data, size * count);
trace_kvm_pio(KVM_PIO_IN, vcpu->arch.pio.port, size, count, vcpu->arch.pio_data);
vcpu->arch.pio.count = 0;
@ -7654,16 +7656,11 @@ 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.
*/
} else {
int r = __emulator_pio_in(vcpu, size, port, count);
if (!r)
return r;
/* Results already available, fall through. */
complete_emulator_pio_in(vcpu, val);
return 1;
}
complete_emulator_pio_in(vcpu, val);
return 1;
return __emulator_pio_in(vcpu, size, port, val, count);
}
static int emulator_pio_in_emulated(struct x86_emulate_ctxt *ctxt,
@ -7678,14 +7675,8 @@ 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,
@ -13245,7 +13236,7 @@ static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
/* memcpy done already by emulator_pio_out. */
vcpu->arch.sev_pio_count -= count;
vcpu->arch.sev_pio_data += count * vcpu->arch.pio.size;
vcpu->arch.sev_pio_data += count * size;
if (!ret)
break;
@ -13261,20 +13252,20 @@ 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;
@ -13286,11 +13277,11 @@ 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;
}