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From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: fwilhelm@google.com, seanjc@google.com, oupton@google.com,
	stable@vger.kernel.org
Subject: [PATCH 8/8] KVM: SEV-ES: go over the sev_pio_data buffer in multiple passes if needed
Date: Wed, 13 Oct 2021 12:56:16 -0400	[thread overview]
Message-ID: <20211013165616.19846-9-pbonzini@redhat.com> (raw)
In-Reply-To: <20211013165616.19846-1-pbonzini@redhat.com>

The PIO scratch buffer is larger than a single page, and therefore
it is not possible to copy it in a single step to vcpu->arch/pio_data.
Bound each call to emulator_pio_in/out to a single page; keep
track of how many I/O operations are left in vcpu->arch.sev_pio_count,
so that the operation can be restarted in the complete_userspace_io
callback.

For OUT, this means that the previous kvm_sev_es_outs implementation
becomes an iterator of the loop, and we can consume the sev_pio_data
buffer before leaving to userspace.

For IN, instead, consuming the buffer and decreasing sev_pio_count
is always done in the complete_userspace_io callback, because that
is when the memcpy is done into sev_pio_data.

Cc: stable@vger.kernel.org
Fixes: 7ed9abfe8e9f ("KVM: SVM: Support string IO operations for an SEV-ES guest")
Reported-by: Felix Wilhelm <fwilhelm@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/x86.c              | 73 +++++++++++++++++++++++++--------
 2 files changed, 57 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6bed6c416c6c..5a0298aa56ba 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -703,6 +703,7 @@ struct kvm_vcpu_arch {
 	struct kvm_pio_request pio;
 	void *pio_data;
 	void *sev_pio_data;
+	unsigned sev_pio_count;
 
 	u8 event_exit_inst_len;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a485e185ad00..09c1e64495d3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12378,38 +12378,76 @@ int kvm_sev_es_mmio_read(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned int bytes,
 EXPORT_SYMBOL_GPL(kvm_sev_es_mmio_read);
 
 static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
-			   unsigned int port, unsigned int count)
+			   unsigned int port);
+
+static int complete_sev_es_emulated_outs(struct kvm_vcpu *vcpu)
 {
-	int ret = emulator_pio_out(vcpu, size, port,
-				   vcpu->arch.sev_pio_data, count);
+	vcpu->arch.pio.count = 0;
+	if (vcpu->arch.sev_pio_count)
+		return kvm_sev_es_outs(vcpu,
+				       vcpu->arch.pio.size,
+				       vcpu->arch.pio.port);
+	return 1;
+}
+
+static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
+			   unsigned int port)
+{
+	for (;;) {
+		unsigned int count =
+			min_t(unsigned int, PAGE_SIZE / size, vcpu->arch.sev_pio_count);
+		int ret = emulator_pio_out(vcpu, size, port, vcpu->arch.sev_pio_data, count);
+
+		/* memcpy done already by emulator_pio_out.  */
+		vcpu->arch.sev_pio_count -= count;
+		vcpu->arch.sev_pio_data += count * vcpu->arch.pio.size;
+		if (!ret)
+			break;
 
-	if (ret) {
 		/* Emulation done by the kernel.  */
-		return ret;
+		vcpu->arch.pio.count = 0;
+		if (!vcpu->arch.sev_pio_count)
+			return 1;
 	}
 
-	vcpu->arch.pio.count = 0;
+	vcpu->arch.complete_userspace_io = complete_sev_es_emulated_outs;
 	return 0;
 }
 
-static int complete_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
+static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size,
+			  unsigned int port);
+
+static void __complete_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
 {
-	memcpy(vcpu->arch.sev_pio_data, vcpu->arch.pio_data,
-	       vcpu->arch.pio.count * vcpu->arch.pio.size);
-	vcpu->arch.pio.count = 0;
+	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;
+}
 
+static int complete_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
+{
+	__complete_sev_es_emulated_ins(vcpu);
+	if (vcpu->arch.sev_pio_count)
+		return kvm_sev_es_ins(vcpu,
+				      vcpu->arch.pio.size,
+				      vcpu->arch.pio.port);
 	return 1;
 }
 
 static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size,
-			  unsigned int port, unsigned int count)
+			  unsigned int port)
 {
-	int ret = emulator_pio_in(vcpu, size, port,
-				  vcpu->arch.sev_pio_data, count);
+	for (;;) {
+		unsigned int count =
+			min_t(unsigned int, PAGE_SIZE / size, vcpu->arch.sev_pio_count);
+		if (!__emulator_pio_in(vcpu, size, port, count))
+			break;
 
-	if (ret) {
 		/* Emulation done by the kernel.  */
-		return ret;
+		__complete_sev_es_emulated_ins(vcpu);
+		if (!vcpu->arch.sev_pio_count)
+			return 1;
 	}
 
 	vcpu->arch.complete_userspace_io = complete_sev_es_emulated_ins;
@@ -12421,8 +12459,9 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
 			 int in)
 {
 	vcpu->arch.sev_pio_data = data;
-	return in ? kvm_sev_es_ins(vcpu, size, port, count)
-		  : kvm_sev_es_outs(vcpu, size, port, count);
+	vcpu->arch.sev_pio_count = count;
+	return in ? kvm_sev_es_ins(vcpu, size, port)
+		  : kvm_sev_es_outs(vcpu, size, port);
 }
 EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
 
-- 
2.27.0


  parent reply	other threads:[~2021-10-13 16:56 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-13 16:56 [PATCH 0/8] KVM: SEV-ES: fixes for string I/O emulation Paolo Bonzini
2021-10-13 16:56 ` [PATCH 1/8] KVM: SEV-ES: fix length of string I/O Paolo Bonzini
2021-10-14 20:13   ` Tom Lendacky
2021-10-21 23:10   ` Maxim Levitsky
2021-10-25  1:31   ` Marc Orr
2021-10-25  8:59     ` Paolo Bonzini
2021-10-13 16:56 ` [PATCH 2/8] KVM: SEV-ES: rename guest_ins_data to sev_pio_data Paolo Bonzini
2021-10-21 23:12   ` Maxim Levitsky
2021-10-13 16:56 ` [PATCH 3/8] KVM: x86: leave vcpu->arch.pio.count alone in emulator_pio_in_out Paolo Bonzini
2021-10-21 23:12   ` Maxim Levitsky
2021-10-13 16:56 ` [PATCH 4/8] KVM: SEV-ES: clean up kvm_sev_es_ins/outs Paolo Bonzini
2021-10-21 23:14   ` Maxim Levitsky
2021-10-22 16:31     ` Paolo Bonzini
2021-10-13 16:56 ` [PATCH 5/8] KVM: x86: split the two parts of emulator_pio_in Paolo Bonzini
2021-10-21 23:14   ` Maxim Levitsky
2021-10-13 16:56 ` [PATCH 6/8] KVM: x86: remove unnecessary arguments from complete_emulator_pio_in Paolo Bonzini
2021-10-21 23:14   ` Maxim Levitsky
2021-10-13 16:56 ` [PATCH 7/8] KVM: SEV-ES: keep INS functions together Paolo Bonzini
2021-10-21 23:14   ` Maxim Levitsky
2021-10-13 16:56 ` Paolo Bonzini [this message]
2021-10-21 23:15   ` [PATCH 8/8] KVM: SEV-ES: go over the sev_pio_data buffer in multiple passes if needed Maxim Levitsky
2021-10-21 17:47 ` [PATCH 0/8] KVM: SEV-ES: fixes for string I/O emulation Paolo Bonzini
2021-10-21 20:04   ` Sean Christopherson
2021-10-21 23:49 ` Sean Christopherson
2021-10-22 13:33   ` Paolo Bonzini

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