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hw/i386/vmport: Set EAX to -1 on failed and unsupported commands

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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.leshchenko@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Message-Id: <20200312165431.82118-5-liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Liran Alon 2020-03-12 18:54:19 +02:00 committed by Paolo Bonzini
parent b889212973
commit 0342ee761e
2 changed files with 16 additions and 4 deletions
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1
hw/core/machine.c
View File

@ -44,6 +44,7 @@ GlobalProperty hw_compat_4_2[] = {
{ "qxl-vga", "revision", "4" },
{ "fw_cfg", "acpi-mr-restore", "false" },
{ "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);

15
hw/i386/vmport.c
View File

@ -45,8 +45,11 @@
/* Compatibility flags for migration */
#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:
/*
@ -168,6 +177,8 @@ 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(),
};