On Mon, Jan 23, 2012 at 05:10:48PM +0100, Kevin Wolf wrote:
> Task switches can switch between Protected Mode and VM86. The current
> mode must be updated during the task switch emulation so that the new
> segment selectors are interpreted correctly and privilege checks
> succeed.
>
> Signed-off-by: Kevin Wolf <kwolf@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_emulate.h | 1 +
> arch/x86/kvm/emulate.c | 17 +++++++++++++++++
> arch/x86/kvm/x86.c | 6 ++++++
> 3 files changed, 24 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
> index c8a9cf3..4a21c7d 100644
> --- a/arch/x86/include/asm/kvm_emulate.h
> +++ b/arch/x86/include/asm/kvm_emulate.h
> @@ -176,6 +176,7 @@ struct x86_emulate_ops {
> void (*set_idt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
> ulong (*get_cr)(struct x86_emulate_ctxt *ctxt, int cr);
> int (*set_cr)(struct x86_emulate_ctxt *ctxt, int cr, ulong val);
> + void (*set_rflags)(struct x86_emulate_ctxt *ctxt, ulong val);
> int (*cpl)(struct x86_emulate_ctxt *ctxt);
> int (*get_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong *dest);
> int (*set_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong value);
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 833969e..52fce89 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2273,6 +2273,23 @@ static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
> return emulate_gp(ctxt, 0);
> ctxt->_eip = tss->eip;
> ctxt->eflags = tss->eflags | 2;
> +
> + /*
> + * If we're switching between Protected Mode and VM86, we need to make
> + * sure to update the mode before loading the segment descriptors so
> + * that the selectors are interpreted correctly.
> + *
> + * Need to get it to the vcpu struct immediately because it influences
> + * the CPL which is checked when loading the segment descriptors.
This is true only for VMX. SVM does not look at rflags. May be instead
of adding new x86_emulate_ops callback we need to get rid of get_cpl()
one and implement CPL checking using emulate.c:get_segment_selector().
> + */
> + if (ctxt->eflags & X86_EFLAGS_VM)
> + ctxt->mode = X86EMUL_MODE_VM86;
> + else
> + ctxt->mode = X86EMUL_MODE_PROT32;
> +
> + ctxt->ops->set_rflags(ctxt, ctxt->eflags);
> +
> + /* General purpose registers */
> ctxt->regs[VCPU_REGS_RAX] = tss->eax;
> ctxt->regs[VCPU_REGS_RCX] = tss->ecx;
> ctxt->regs[VCPU_REGS_RDX] = tss->edx;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index dc3e945..502b5c3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4040,6 +4040,11 @@ static int emulator_set_cr(struct x86_emulate_ctxt *ctxt, int cr, ulong val)
> return res;
> }
>
> +static void emulator_set_rflags(struct x86_emulate_ctxt *ctxt, ulong val)
> +{
> + kvm_set_rflags(emul_to_vcpu(ctxt), val);
> +}
> +
> static int emulator_get_cpl(struct x86_emulate_ctxt *ctxt)
> {
> return kvm_x86_ops->get_cpl(emul_to_vcpu(ctxt));
> @@ -4199,6 +4204,7 @@ static struct x86_emulate_ops emulate_ops = {
> .set_idt = emulator_set_idt,
> .get_cr = emulator_get_cr,
> .set_cr = emulator_set_cr,
> + .set_rflags = emulator_set_rflags,
> .cpl = emulator_get_cpl,
> .get_dr = emulator_get_dr,
> .set_dr = emulator_set_dr,
> --
> 1.7.6.5
--
Gleb.
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