KVM: SEV-ES: go over the sev_pio_data buffer in multiple passes if needed

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>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6bed6c4..5a0298a 100644 (file)
--- 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 23e7724..b26647a 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12386,38 +12386,77 @@ 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);
+       int size = vcpu->arch.pio.size;
+       int port = vcpu->arch.pio.port;
+
+       vcpu->arch.pio.count = 0;
+       if (vcpu->arch.sev_pio_count)
+               return kvm_sev_es_outs(vcpu, size, 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;
+               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 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)
+{
+       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)
 {
-       memcpy(vcpu->arch.sev_pio_data, vcpu->arch.pio_data,
-              vcpu->arch.pio.count * vcpu->arch.pio.size);
-       vcpu->arch.pio.count = 0;
+       int size = vcpu->arch.pio.size;
+       int port = vcpu->arch.pio.port;
 
+       advance_sev_es_emulated_ins(vcpu);
+       if (vcpu->arch.sev_pio_count)
+               return kvm_sev_es_ins(vcpu, size, 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;
+               advance_sev_es_emulated_ins(vcpu);
+               if (!vcpu->arch.sev_pio_count)
+                       return 1;
        }
 
        vcpu->arch.complete_userspace_io = complete_sev_es_emulated_ins;
@@ -12429,8 +12468,9 @@ 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);