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 | 32 +++++++++++++++++++++++++++++--- 2 files changed, 30 insertions(+), 3 deletions(-) diff --git a/hw/core/machine.c b/hw/core/machine.c index 9e8c06036faf..0496112b741c 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", "x-read-set-eax", "off" }, }; 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 6ed110ef71a6..72f09ef5cba3 100644 --- a/hw/i386/vmport.c +++ b/hw/i386/vmport.c @@ -43,6 +43,11 @@ #define VMPORT_ENTRIES 0x2c #define VMPORT_MAGIC 0x564D5868 +/* Compatibility flags for migration */ +#define VMPORT_COMPAT_READ_SET_EAX_BIT 0 +#define VMPORT_COMPAT_READ_SET_EAX \ + (1 << VMPORT_COMPAT_READ_SET_EAX_BIT) + #define VMPORT(obj) OBJECT_CHECK(VMPortState, (obj), TYPE_VMPORT) typedef struct VMPortState { @@ -51,6 +56,8 @@ typedef struct VMPortState { MemoryRegion io; VMPortReadFunc *func[VMPORT_ENTRIES]; void *opaque[VMPORT_ENTRIES]; + + uint32_t compat_flags; } VMPortState; static VMPortState *port_state; @@ -80,17 +87,33 @@ 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->compat_flags & VMPORT_COMPAT_READ_SET_EAX) { + cpu->env.regs[R_EAX] = eax; + } + + return eax; } static void vmport_ioport_write(void *opaque, hwaddr addr, @@ -163,6 +186,9 @@ static void vmport_realizefn(DeviceState *dev, Error **errp) } static Property vmport_properties[] = { + /* Used to enforce compatibility for migration */ + DEFINE_PROP_BIT("x-read-set-eax", VMPortState, compat_flags, + VMPORT_COMPAT_READ_SET_EAX_BIT, true), DEFINE_PROP_END_OF_LIST(), }; -- 2.20.1