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

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>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 368d0d4..716ae5c 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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;
        }