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Commit 10e38fc7 authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
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KVM: x86: Emulator flag for instruction that only support 16-bit addresses in real mode 



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: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 44583cba

arch/x86/kvm/emulate.c

+7 −1
Original line number Diff line number Diff line
@@ -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;