vmport_ioport_read() returns the value that should propagate to vCPU EAX register when guest reads VMPort IOPort (i.e. By x86 IN instruction).
However, because vmport_ioport_read() calls cpu_synchronize_state(), the returned value gets overridden by the value in QEMU vCPU EAX register. i.e. cpu->env.regs[R_EAX]. To fix this issue, change vmport_ioport_read() to explicitly override cpu->env.regs[R_EAX] with the value it wish to propagate to vCPU EAX register. Reviewed-by: Nikita Leshenko <nikita.leshche...@oracle.com> Signed-off-by: Liran Alon <liran.a...@oracle.com> --- hw/core/machine.c | 1 + hw/i386/vmport.c | 24 ++++++++++++++++++++---- 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/hw/core/machine.c b/hw/core/machine.c index 9e8c06036faf..b9da40460d52 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -39,6 +39,7 @@ GlobalProperty hw_compat_4_2[] = { { "usb-redir", "suppress-remote-wake", "off" }, { "qxl", "revision", "4" }, { "qxl-vga", "revision", "4" }, + { "vmport", "version", "1" }, }; const size_t hw_compat_4_2_len = G_N_ELEMENTS(hw_compat_4_2); diff --git a/hw/i386/vmport.c b/hw/i386/vmport.c index ca4d95fc017f..736d78263889 100644 --- a/hw/i386/vmport.c +++ b/hw/i386/vmport.c @@ -75,17 +75,33 @@ static uint64_t vmport_ioport_read(void *opaque, hwaddr addr, eax = env->regs[R_EAX]; if (eax != VMPORT_MAGIC) { - return eax; + goto out; } command = env->regs[R_ECX]; trace_vmport_command(command); if (command >= VMPORT_ENTRIES || !s->func[command]) { qemu_log_mask(LOG_UNIMP, "vmport: unknown command %x\n", command); - return eax; + goto out; } - return s->func[command](s->opaque[command], addr); + eax = s->func[command](s->opaque[command], addr); + +out: + /* + * The call above to cpu_synchronize_state() gets vCPU registers values + * to QEMU but also cause QEMU to write QEMU vCPU registers values to + * vCPU implementation (e.g. Accelerator such as KVM) just before + * resuming guest. + * + * Therefore, in order to make IOPort return value propagate to + * guest EAX, we need to explicitly update QEMU EAX register value. + */ + if (s->version > 1) { + cpu->env.regs[R_EAX] = eax; + } + + return eax; } static void vmport_ioport_write(void *opaque, hwaddr addr, @@ -163,7 +179,7 @@ static Property vmport_properties[] = { * On every guest-visible change, should make changes conditioned on * version and define proper version for previous machine-types. */ - DEFINE_PROP_UINT8("version", VMPortState, version, 1), + DEFINE_PROP_UINT8("version", VMPortState, version, 2), DEFINE_PROP_END_OF_LIST(), }; -- 2.20.1