[PATCH 5.14 114/169] KVM: x86: split the two parts of emulator_pio_in

Greg Kroah-Hartman
2021-10-25T19:53:45Z

From: Paolo Bonzini <pbonzini@redhat.com>

commit 3b27de27183911d461afedf50c6fa30c59740c07 upstream.

emulator_pio_in handles both the case where the data is pending in
vcpu->arch.pio.count, and the case where I/O has to be done via either
an in-kernel device or a userspace exit. For SEV-ES we would like
to split these, to identify clearly the moment at which the
sev_pio_data is consumed. To this end, create two different
functions: __emulator_pio_in fills in vcpu->arch.pio.count, while
complete_emulator_pio_in clears it and releases vcpu->arch.pio.data.

Because this patch has to be backported, things are left a bit messy.
kernel_pio() operates on vcpu->arch.pio, which leads to emulator_pio_in()
having with two calls to complete_emulator_pio_in(). It will be fixed
in the next release.

While at it, remove the unused void* val argument of emulator_pio_in_out.
The function currently hardcodes vcpu->arch.pio_data as the
source/destination buffer, which sucks but will be fixed after the more
severe SEV-ES buffer overflow.

No functional change intended.

Cc: stable@vger.kernel.org
Fixes: 7ed9abfe8e9f ("KVM: SVM: Support string IO operations for an SEV-ES guest")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/x86.c | 45 ++++++++++++++++++++++++++++-----------------
1 file changed, 28 insertions(+), 17 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6907,7 +6907,7 @@ static int kernel_pio(struct kvm_vcpu *v
}

static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
- unsigned short port, void *val,
+ unsigned short port,
unsigned int count, bool in)
{
vcpu->arch.pio.port = port;
@@ -6928,26 +6928,38 @@ static int emulator_pio_in_out(struct kv
return 0;
}

-static int emulator_pio_in(struct kvm_vcpu *vcpu, int size,
- unsigned short port, void *val, unsigned int count)
+static int __emulator_pio_in(struct kvm_vcpu *vcpu, int size,
+ unsigned short port, unsigned int count)
{
- int ret;
+ WARN_ON(vcpu->arch.pio.count);
+ memset(vcpu->arch.pio_data, 0, size * count);
+ return emulator_pio_in_out(vcpu, size, port, count, true);
+}

- if (vcpu->arch.pio.count)
- goto data_avail;
+static void complete_emulator_pio_in(struct kvm_vcpu *vcpu, int size,
+ unsigned short port, void *val)
+{
+ memcpy(val, vcpu->arch.pio_data, size * vcpu->arch.pio.count);
+ trace_kvm_pio(KVM_PIO_IN, port, size, vcpu->arch.pio.count, vcpu->arch.pio_data);
+ vcpu->arch.pio.count = 0;
+}

- memset(vcpu->arch.pio_data, 0, size * count);
+static int emulator_pio_in(struct kvm_vcpu *vcpu, int size,
+ unsigned short port, void *val, unsigned int count)
+{
+ if (vcpu->arch.pio.count) {
+ /* Complete previous iteration. */
+ } else {
+ int r = __emulator_pio_in(vcpu, size, port, count);
+ if (!r)
+ return r;

- ret = emulator_pio_in_out(vcpu, size, port, val, count, true);
- if (ret) {
-data_avail:
- memcpy(val, vcpu->arch.pio_data, size * count);
- trace_kvm_pio(KVM_PIO_IN, port, size, count, vcpu->arch.pio_data);
- vcpu->arch.pio.count = 0;
- return 1;
+ /* Results already available, fall through. */
}

- return 0;
+ WARN_ON(count != vcpu->arch.pio.count);
+ complete_emulator_pio_in(vcpu, size, port, val);
+ return 1;
}

static int emulator_pio_in_emulated(struct x86_emulate_ctxt *ctxt,
@@ -6966,12 +6978,11 @@ static int emulator_pio_out(struct kvm_v

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, (void *)val, count, false);
+ ret = emulator_pio_in_out(vcpu, size, port, count, false);
if (ret)
vcpu->arch.pio.count = 0;

return ret;
-
}

static int emulator_pio_out_emulated(struct x86_emulate_ctxt *ctxt,