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KVM: x86: fix RSM into 64-bit protected mode

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In order to get into 64-bit protected mode, you need to enable
paging while EFER.LMA=1.  For this to work, CS.L must be 0.
Currently, we load the segments before CR0 and CR4, which means
that if RSM returns into 64-bit protected mode CS.L is already 1
and everything breaks.

Luckily, CS.L=0 is always the case when executing RSM, because it
is forbidden to execute RSM from 64-bit protected mode.  Hence it
is enough to load CR0 and CR4 first, and only then the segments.

Fixes: 660a5d517aaab9187f93854425c4c63f4a09195c
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-10-14 15:25:52 +02:00
parent 25188b9986
commit b10d92a54d
1 changed files with 7 additions and 3 deletions
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10
arch/x86/kvm/emulate.c
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@ -2418,7 +2418,7 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt, u64 smbase)
u64 val, cr0, cr4; u64 val, cr0, cr4;
u32 base3; u32 base3;
u16 selector; u16 selector;
int i; int i, r;
for (i = 0; i < 16; i++) for (i = 0; i < 16; i++)
*reg_write(ctxt, i) = GET_SMSTATE(u64, smbase, 0x7ff8 - i * 8); *reg_write(ctxt, i) = GET_SMSTATE(u64, smbase, 0x7ff8 - i * 8);
@ -2460,13 +2460,17 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt, u64 smbase)
dt.address = GET_SMSTATE(u64, smbase, 0x7e68); dt.address = GET_SMSTATE(u64, smbase, 0x7e68);
ctxt->ops->set_gdt(ctxt, &dt); ctxt->ops->set_gdt(ctxt, &dt);
r = rsm_enter_protected_mode(ctxt, cr0, cr4);
if (r != X86EMUL_CONTINUE)
return r;
for (i = 0; i < 6; i++) { for (i = 0; i < 6; i++) {
int r = rsm_load_seg_64(ctxt, smbase, i); r = rsm_load_seg_64(ctxt, smbase, i);
if (r != X86EMUL_CONTINUE) if (r != X86EMUL_CONTINUE)
return r; return r;
} }
return rsm_enter_protected_mode(ctxt, cr0, cr4); return X86EMUL_CONTINUE;
} }
static int em_rsm(struct x86_emulate_ctxt *ctxt) static int em_rsm(struct x86_emulate_ctxt *ctxt)