Commit 9646f492 authored by Eduardo Habkost's avatar Eduardo Habkost
Browse files

target-i386: Don't try to enable PT State xsave component 



The code that calculates the set of supported XSAVE components on
CPUID looks at ext_save_areas to find out which components should
be enabled. However, if there are zeroed entries in the
ext_save_areas array, the
  ((env->features[esa->feature] & esa->bits) == esa->bits)
check will always succeed and QEMU will unconditionally try to
enable the component.

Luckily this never caused any problems because the only missing
entry in ext_save_areas is the PT State component (bit 8), and
KVM currently doesn't support it (so it was cleared on ena_mask).
But the code was still incorrect and would break if KVM starts
returning CPUID[EAX=0xD,ECX=0].EAX[bit 8] as supported on
GET_SUPPORTED_CPUID.

Fix the problem by changing the code to not enable a XSAVE
component if ExtSaveArea::bits is zero.

Reviewed-by: default avatarRichard Henderson <rth@twiddle.net>
Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
parent 2d5312da

target-i386/cpu.c

+3 −3
Original line number Diff line number Diff line
@@ -2514,7 +2514,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, 
            *ecx = 0x240;

            for (i = 2; i < ARRAY_SIZE(x86_ext_save_areas); i++) {

                const ExtSaveArea *esa = &x86_ext_save_areas[i];

                if ((env->features[esa->feature] & esa->bits) == esa->bits

                if ((env->features[esa->feature] & esa->bits)

                    && ((ena_mask >> i) & 1) != 0) {

                    if (i < 32) {

                        *eax |= 1u << i;
@@ -2530,7 +2530,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, 
            *eax = env->features[FEAT_XSAVE];

        } else if (count < ARRAY_SIZE(x86_ext_save_areas)) {

            const ExtSaveArea *esa = &x86_ext_save_areas[count];

            if ((env->features[esa->feature] & esa->bits) == esa->bits

            if ((env->features[esa->feature] & esa->bits)

                && ((ena_mask >> count) & 1) != 0) {

                *eax = esa->size;

                *ebx = esa->offset;
@@ -2766,7 +2766,7 @@ static void x86_cpu_reset(CPUState *s) 
    }

    for (i = 2; i < ARRAY_SIZE(x86_ext_save_areas); i++) {

        const ExtSaveArea *esa = &x86_ext_save_areas[i];

        if ((env->features[esa->feature] & esa->bits) == esa->bits) {

        if (env->features[esa->feature] & esa->bits) {

            xcr0 |= 1ull << i;

        }

    }