On Wed, 2021-10-13 at 12:56 -0400, Paolo Bonzini wrote:
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);} 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);
I might have missed something, but it looks OK to me. i mostly checked how the code looks after applying this patch.
Reviewed-by: Maxim Levitsky mlevitsk@redhat.com
Note that I haven't run tested the patches as I don't currently test SEV-ES.
Best regards, Maxim Levitsky