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kvm: x86: Save/restore FPU OP, IP and DP 

These FPU states are properly maintained by KVM but not yet by TCG. So
far we unconditionally set them to 0 in the guest which may cause
state corruptions, though not with modern guests.

To avoid breaking backward migration, use a conditional subsection that
is only written if any of the three fields is non-zero. The guest's
FNINIT clears them frequently, and cleared IA32_MISC_ENABLE MSR[2]
reduces the probability of non-zero values further so that this
subsection is not expected to restrict migration in any common scenario.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Jan Kiszka 2011-06-15 15:17:26 +02:00 committed by Avi Kivity
parent eb47d7c5d9
commit 42cc8fa620
3 changed files with 42 additions and 5 deletions
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4
target-i386/cpu.h
View File

@ -641,6 +641,10 @@ typedef struct CPUX86State {
uint16_t fpuc;
uint8_t fptags[8]; /* 0 = valid, 1 = empty */
FPReg fpregs[8];
/* KVM-only so far */
uint16_t fpop;
uint64_t fpip;
uint64_t fpdp;
/* emulator internal variables */
float_status fp_status;

20
target-i386/kvm.c
View File

@ -753,6 +753,9 @@ static int kvm_put_fpu(CPUState *env)
fpu.fsw = env->fpus & ~(7 << 11);
fpu.fsw |= (env->fpstt & 7) << 11;
fpu.fcw = env->fpuc;
fpu.last_opcode = env->fpop;
fpu.last_ip = env->fpip;
fpu.last_dp = env->fpdp;
for (i = 0; i < 8; ++i) {
fpu.ftwx |= (!env->fptags[i]) << i;
}
@ -778,7 +781,7 @@ static int kvm_put_xsave(CPUState *env)
#ifdef KVM_CAP_XSAVE
int i, r;
struct kvm_xsave* xsave;
uint16_t cwd, swd, twd, fop;
uint16_t cwd, swd, twd;
if (!kvm_has_xsave()) {
return kvm_put_fpu(env);
@ -786,7 +789,7 @@ static int kvm_put_xsave(CPUState *env)
xsave = qemu_memalign(4096, sizeof(struct kvm_xsave));
memset(xsave, 0, sizeof(struct kvm_xsave));
cwd = swd = twd = fop = 0;
cwd = swd = twd = 0;
swd = env->fpus & ~(7 << 11);
swd |= (env->fpstt & 7) << 11;
cwd = env->fpuc;
@ -794,7 +797,9 @@ static int kvm_put_xsave(CPUState *env)
twd |= (!env->fptags[i]) << i;
}
xsave->region[0] = (uint32_t)(swd << 16) + cwd;
xsave->region[1] = (uint32_t)(fop << 16) + twd;
xsave->region[1] = (uint32_t)(env->fpop << 16) + twd;
memcpy(&xsave->region[XSAVE_CWD_RIP], &env->fpip, sizeof(env->fpip));
memcpy(&xsave->region[XSAVE_CWD_RDP], &env->fpdp, sizeof(env->fpdp));
memcpy(&xsave->region[XSAVE_ST_SPACE], env->fpregs,
sizeof env->fpregs);
memcpy(&xsave->region[XSAVE_XMM_SPACE], env->xmm_regs,
@ -970,6 +975,9 @@ static int kvm_get_fpu(CPUState *env)
env->fpstt = (fpu.fsw >> 11) & 7;
env->fpus = fpu.fsw;
env->fpuc = fpu.fcw;
env->fpop = fpu.last_opcode;
env->fpip = fpu.last_ip;
env->fpdp = fpu.last_dp;
for (i = 0; i < 8; ++i) {
env->fptags[i] = !((fpu.ftwx >> i) & 1);
}
@ -985,7 +993,7 @@ static int kvm_get_xsave(CPUState *env)
#ifdef KVM_CAP_XSAVE
struct kvm_xsave* xsave;
int ret, i;
uint16_t cwd, swd, twd, fop;
uint16_t cwd, swd, twd;
if (!kvm_has_xsave()) {
return kvm_get_fpu(env);
@ -1001,13 +1009,15 @@ static int kvm_get_xsave(CPUState *env)
cwd = (uint16_t)xsave->region[0];
swd = (uint16_t)(xsave->region[0] >> 16);
twd = (uint16_t)xsave->region[1];
fop = (uint16_t)(xsave->region[1] >> 16);
env->fpop = (uint16_t)(xsave->region[1] >> 16);
env->fpstt = (swd >> 11) & 7;
env->fpus = swd;
env->fpuc = cwd;
for (i = 0; i < 8; ++i) {
env->fptags[i] = !((twd >> i) & 1);
}
memcpy(&env->fpip, &xsave->region[XSAVE_CWD_RIP], sizeof(env->fpip));
memcpy(&env->fpdp, &xsave->region[XSAVE_CWD_RDP], sizeof(env->fpdp));
env->mxcsr = xsave->region[XSAVE_MXCSR];
memcpy(env->fpregs, &xsave->region[XSAVE_ST_SPACE],
sizeof env->fpregs);

23
target-i386/machine.c
View File

@ -290,6 +290,26 @@ static const VMStateDescription vmstate_async_pf_msr = {
}
};
static bool fpop_ip_dp_needed(void *opaque)
{
CPUState *env = opaque;
return env->fpop != 0 || env->fpip != 0 || env->fpdp != 0;
}
static const VMStateDescription vmstate_fpop_ip_dp = {
.name = "cpu/fpop_ip_dp",
.version_id = 1,
.minimum_version_id = 1,
.minimum_version_id_old = 1,
.fields = (VMStateField []) {
VMSTATE_UINT16_V(fpop, CPUState, 13),
VMSTATE_UINT64_V(fpip, CPUState, 13),
VMSTATE_UINT64_V(fpdp, CPUState, 13),
VMSTATE_END_OF_LIST()
}
};
static const VMStateDescription vmstate_cpu = {
.name = "cpu",
.version_id = CPU_SAVE_VERSION,
@ -397,6 +417,9 @@ static const VMStateDescription vmstate_cpu = {
{
.vmsd = &vmstate_async_pf_msr,
.needed = async_pf_msr_needed,
} , {
.vmsd = &vmstate_fpop_ip_dp,
.needed = fpop_ip_dp_needed,
} , {
/* empty */
}