This is used as a signal for VMware Tools to know if a command it attempted to invoke, failed or is unsupported. As a result, VMware Tools will either report failure to user or fallback to another backdoor command in attempt to perform some operation.
A few examples: * open-vm-tools TimeSyncReadHost() function fallbacks to CMD_GETTIMEFULL command when CMD_GETTIMEFULL_WITH_LAG fails/unsupported. * open-vm-tools Hostinfo_NestingSupported() function verifies EAX != -1 to check for success. * open-vm-tools Hostinfo_VCPUInfoBackdoor() functions checks if reserved-bit is set to indicate command is unimplemented. 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 | 19 +++++++++++++++---- 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/hw/core/machine.c b/hw/core/machine.c index 0496112b741c..2595a13e5650 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -40,6 +40,7 @@ GlobalProperty hw_compat_4_2[] = { { "qxl", "revision", "4" }, { "qxl-vga", "revision", "4" }, { "vmport", "x-read-set-eax", "off" }, + { "vmport", "x-signal-unsupported-cmd", "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 72f09ef5cba3..e67c7bb2afea 100644 --- a/hw/i386/vmport.c +++ b/hw/i386/vmport.c @@ -44,9 +44,12 @@ #define VMPORT_MAGIC 0x564D5868 /* Compatibility flags for migration */ -#define VMPORT_COMPAT_READ_SET_EAX_BIT 0 -#define VMPORT_COMPAT_READ_SET_EAX \ +#define VMPORT_COMPAT_READ_SET_EAX_BIT 0 +#define VMPORT_COMPAT_SIGNAL_UNSUPPORTED_CMD_BIT 1 +#define VMPORT_COMPAT_READ_SET_EAX \ (1 << VMPORT_COMPAT_READ_SET_EAX_BIT) +#define VMPORT_COMPAT_SIGNAL_UNSUPPORTED_CMD \ + (1 << VMPORT_COMPAT_SIGNAL_UNSUPPORTED_CMD_BIT) #define VMPORT(obj) OBJECT_CHECK(VMPortState, (obj), TYPE_VMPORT) @@ -87,17 +90,23 @@ static uint64_t vmport_ioport_read(void *opaque, hwaddr addr, eax = env->regs[R_EAX]; if (eax != VMPORT_MAGIC) { - goto out; + goto err; } 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); - goto out; + goto err; } eax = s->func[command](s->opaque[command], addr); + goto out; + +err: + if (s->compat_flags & VMPORT_COMPAT_SIGNAL_UNSUPPORTED_CMD) { + eax = UINT32_MAX; + } out: /* @@ -189,6 +198,8 @@ 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_BIT("x-signal-unsupported-cmd", VMPortState, compat_flags, + VMPORT_COMPAT_SIGNAL_UNSUPPORTED_CMD_BIT, true), DEFINE_PROP_END_OF_LIST(), }; -- 2.20.1