linux-kernel - [PATCH 1/6] KVM: x86: inline kernel

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Message-Id: <20220608121253.867333-2-pbonzini@redhat.com>
Date:   Wed,  8 Jun 2022 08:12:48 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     seanjc@...gle.com
Subject: [PATCH 1/6] KVM: x86: inline kernel_pio into its sole caller

The caller of kernel_pio already has arguments for most of what kernel_pio
fishes out of vcpu->arch.pio.  This is the first step towards ensuring that
vcpu->arch.pio.* is only used when exiting to userspace.

We can now also WARN if emulated PIO performs successful in-kernel iterations
before having to fall back to userspace.  The code is not ready for that, and
it should never happen.

No functional change intended.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/x86.c | 39 +++++++++++++++++----------------------
 1 file changed, 17 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 79efdc19b4c8..2f9100f2564e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7415,37 +7415,32 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
 	return emulator_write_emulated(ctxt, addr, new, bytes, exception);
 }
 
-static int kernel_pio(struct kvm_vcpu *vcpu, void *pd)
-{
-	int r = 0, i;
-
-	for (i = 0; i < vcpu->arch.pio.count; i++) {
-		if (vcpu->arch.pio.in)
-			r = kvm_io_bus_read(vcpu, KVM_PIO_BUS, vcpu->arch.pio.port,
-					    vcpu->arch.pio.size, pd);
-		else
-			r = kvm_io_bus_write(vcpu, KVM_PIO_BUS,
-					     vcpu->arch.pio.port, vcpu->arch.pio.size,
-					     pd);
-		if (r)
-			break;
-		pd += vcpu->arch.pio.size;
-	}
-	return r;
-}
-
 static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
 			       unsigned short port,
 			       unsigned int count, bool in)
 {
+	void *data = vcpu->arch.pio_data;
+	unsigned i;
+	int r;
+
 	vcpu->arch.pio.port = port;
 	vcpu->arch.pio.in = in;
-	vcpu->arch.pio.count  = count;
+	vcpu->arch.pio.count = count;
 	vcpu->arch.pio.size = size;
 
-	if (!kernel_pio(vcpu, vcpu->arch.pio_data))
-		return 1;
+	for (i = 0; i < count; i++) {
+		if (in)
+			r = kvm_io_bus_read(vcpu, KVM_PIO_BUS, port, size, data);
+		else
+			r = kvm_io_bus_write(vcpu, KVM_PIO_BUS, port, size, data);
+		if (r)
+			goto userspace_io;
+		data += size;
+	}
+	return 1;
 
+userspace_io:
+	WARN_ON(i != 0);
 	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;
-- 
2.31.1