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hw/i386/vmport: Propagate IOPort read to vCPU EAX register

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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.leshchenko@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Message-Id: <20200312165431.82118-4-liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Liran Alon 2020-03-12 18:54:18 +02:00 committed by Paolo Bonzini
parent c9ab24cef8
commit b889212973
2 changed files with 30 additions and 3 deletions
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1
hw/core/machine.c
View File

@ -43,6 +43,7 @@ GlobalProperty hw_compat_4_2[] = {
{ "qxl", "revision", "4" },
{ "qxl-vga", "revision", "4" },
{ "fw_cfg", "acpi-mr-restore", "false" },
{ "vmport", "x-read-set-eax", "off" },
};
const size_t hw_compat_4_2_len = G_N_ELEMENTS(hw_compat_4_2);

32
hw/i386/vmport.c
View File

@ -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,
@ -142,6 +165,9 @@ 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(),
};