diff options
| author | Wanpeng Li <wanpeng.li@hotmail.com> | 2017-11-05 16:54:47 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-02-03 17:05:36 +0100 |
| commit | ec73d16bc7ce352375052d81a22bbb53e3eccabe (patch) | |
| tree | 926d9790fc682a13f60b036f54fdb8fd806ce968 /arch | |
| parent | 114de9bfefa5aee862815b0ae7453d40bf5278c2 (diff) | |
KVM: X86: Fix operand/address-size during instruction decoding
[ Upstream commit 3853be2603191829b442b64dac6ae8ba0c027bf9 ]
Pedro reported:
During tests that we conducted on KVM, we noticed that executing a "PUSH %ES"
instruction under KVM produces different results on both memory and the SP
register depending on whether EPT support is enabled. With EPT the SP is
reduced by 4 bytes (and the written value is 0-padded) but without EPT support
it is only reduced by 2 bytes. The difference can be observed when the CS.DB
field is 1 (32-bit) but not when it's 0 (16-bit).
The internal segment descriptor cache exist even in real/vm8096 mode. The CS.D
also should be respected instead of just default operand/address-size/66H
prefix/67H prefix during instruction decoding. This patch fixes it by also
adjusting operand/address-size according to CS.D.
Reported-by: Pedro Fonseca <pfonseca@cs.washington.edu>
Tested-by: Pedro Fonseca <pfonseca@cs.washington.edu>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Pedro Fonseca <pfonseca@cs.washington.edu>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c8f8dd8ca0a1..6f5a3b076341 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4990,6 +4990,8 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) bool op_prefix = false; bool has_seg_override = false; struct opcode opcode; + u16 dummy; + struct desc_struct desc; ctxt->memop.type = OP_NONE; ctxt->memopp = NULL; @@ -5008,6 +5010,11 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) switch (mode) { case X86EMUL_MODE_REAL: case X86EMUL_MODE_VM86: + def_op_bytes = def_ad_bytes = 2; + ctxt->ops->get_segment(ctxt, &dummy, &desc, NULL, VCPU_SREG_CS); + if (desc.d) + def_op_bytes = def_ad_bytes = 4; + break; case X86EMUL_MODE_PROT16: def_op_bytes = def_ad_bytes = 2; break; |