>From 21f4d5d9048e84d01137ba2a9fbb3d691141dc16 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 21 Oct 2021 15:41:18 -0700 Subject: [PATCH 4/6] KVM: x86: Fill kvm_pio_request if and only if KVM is exiting to userspace Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 89 +++++++++++++++++++++++----------------------- 1 file changed, 45 insertions(+), 44 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a126b1129348..a20a790ce586 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7044,19 +7044,17 @@ 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) +static int kernel_pio(struct kvm_vcpu *vcpu, int size, unsigned short port, + void *data, unsigned int count, bool in) { unsigned int i; int r; - 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); + 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, - vcpu->arch.pio.port, vcpu->arch.pio.size, - pd); + r = kvm_io_bus_write(vcpu, KVM_PIO_BUS, port, size, data); if (r) { /* * The port doesn't change on subsequent iterations and @@ -7065,24 +7063,33 @@ static int kernel_pio(struct kvm_vcpu *vcpu, void *pd) WARN_ON_ONCE(i); return r; } - pd += vcpu->arch.pio.size; + data += size; } return 0; } static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size, - unsigned short port, void *val, + unsigned short port, void *data, unsigned int count, bool in) { + if (!kernel_pio(vcpu, port, size, data, count, in)) + return 1; + + /* + * I/O was not handled in kernel, forward the operation to userespace. + * Snapshot the port, size, etc... in kernel memory as some callers, + * e.g. "fast" port I/O and SEV-ES, don't flow through the emulator and + * will have lost the original information when KVM regains control. + * The info stored in the run page can't be trusted as userspace has + * write access to the run page. + */ 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)) { - vcpu->arch.pio.count = 0; - return 1; - } + if (!in) + 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; @@ -7090,30 +7097,27 @@ static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size, vcpu->run->io.data_offset = KVM_PIO_PAGE_OFFSET * PAGE_SIZE; vcpu->run->io.count = count; vcpu->run->io.port = port; - return 0; } static int emulator_pio_in(struct kvm_vcpu *vcpu, int size, - unsigned short port, void *val, unsigned int count) + unsigned short port, void *data, unsigned int count) { - int ret; - - if (vcpu->arch.pio.count) - goto data_avail; - - memset(vcpu->arch.pio_data, 0, size * count); - - ret = emulator_pio_in_out(vcpu, size, port, val, count, true); - if (ret) { -data_avail: - memcpy(val, vcpu->arch.pio_data, size * count); - trace_kvm_pio(KVM_PIO_IN, port, size, count, vcpu->arch.pio_data); + if (vcpu->arch.pio.count) { + /* + * Complete port I/O when re-emulating the instruction after + * userspace has provided the requested data. + * + * FIXME: this will copy garbage if count > vcpu->arch.pio.count. + */ vcpu->arch.pio.count = 0; - return 1; + memcpy(data, vcpu->arch.pio_data, size * count); + } else if (!emulator_pio_in_out(vcpu, size, port, data, count, true)) { + return 0; } - return 0; + trace_kvm_pio(KVM_PIO_IN, port, size, count, data); + return 1; } static int emulator_pio_in_emulated(struct x86_emulate_ctxt *ctxt, @@ -7125,19 +7129,18 @@ static int emulator_pio_in_emulated(struct x86_emulate_ctxt *ctxt, } static int emulator_pio_out(struct kvm_vcpu *vcpu, int size, - unsigned short port, const void *val, + unsigned short port, void *val, unsigned int count) { - memcpy(vcpu->arch.pio_data, val, size * count); - trace_kvm_pio(KVM_PIO_OUT, port, size, count, vcpu->arch.pio_data); - return emulator_pio_in_out(vcpu, size, port, (void *)val, count, false); + trace_kvm_pio(KVM_PIO_OUT, port, size, count, val); + return emulator_pio_in_out(vcpu, size, port, val, count, false); } static int emulator_pio_out_emulated(struct x86_emulate_ctxt *ctxt, int size, unsigned short port, - const void *val, unsigned int count) + const void *data, unsigned int count) { - return emulator_pio_out(emul_to_vcpu(ctxt), size, port, val, count); + return emulator_pio_out(emul_to_vcpu(ctxt), size, port, (void *)data, count); } static unsigned long get_segment_base(struct kvm_vcpu *vcpu, int seg) @@ -12509,14 +12512,12 @@ static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size, ret = emulator_pio_in_emulated(vcpu->arch.emulate_ctxt, size, port, data, count); - if (ret) { - vcpu->arch.pio.count = 0; - } else { - vcpu->arch.guest_ins_data = data; - vcpu->arch.complete_userspace_io = complete_sev_es_emulated_ins; - } + if (ret) + return ret; - return ret; + vcpu->arch.guest_ins_data = data; + vcpu->arch.complete_userspace_io = complete_sev_es_emulated_ins; + return 0; } int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size, -- 2.33.0.1079.g6e70778dc9-goog