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KVM: x86: Emulator flag for instruction that only support 16-bit addresses in real mode

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Certain instructions, such as monitor and xsave do not support big real mode
and cause a #GP exception if any of the accessed bytes effective address are
not within [0, 0xffff].  This patch introduces a flag to mark these
instructions, including the necassary checks.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2014-06-18 17:19:34 +03:00 committed by Paolo Bonzini
parent 44583cba91
commit 10e38fc7ca
1 changed files with 7 additions and 1 deletions
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8
arch/x86/kvm/emulate.c
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@ -164,6 +164,7 @@
#define NoMod ((u64)1 << 47) /* Mod field is ignored */
#define Intercept ((u64)1 << 48) /* Has valid intercept field */
#define CheckPerm ((u64)1 << 49) /* Has valid check_perm field */
#define NoBigReal ((u64)1 << 50) /* No big real mode */
#define DstXacc (DstAccLo | SrcAccHi | SrcWrite)
@ -640,7 +641,12 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
if (!fetch && (desc.type & 8) && !(desc.type & 2))
goto bad;
lim = desc_limit_scaled(&desc);
if ((desc.type & 8) || !(desc.type & 4)) {
if ((ctxt->mode == X86EMUL_MODE_REAL) && !fetch &&
(ctxt->d & NoBigReal)) {
/* la is between zero and 0xffff */
if (la > 0xffff || (u32)(la + size - 1) > 0xffff)
goto bad;
} else if ((desc.type & 8) || !(desc.type & 4)) {
/* expand-up segment */
if (addr.ea > lim || (u32)(addr.ea + size - 1) > lim)
goto bad;