[PATCH v2 02/12] KVM: x86: tag the instructions which are used to write page table

Xiao Guangrong
2011-08-02T11:05:41Z

The idea is from Avi:
| tag instructions that are typically used to modify the page tables, and drop
| shadow if any other instruction is used
| The list would include, I'd guess, and, or, bts, btc, mov, xchg, cmpxchg, and
| cmpxchg8b

This patch is used to tag the instructions and in the later path, shadow page
is dropped if it is written by other instructions

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/include/asm/kvm_emulate.h | 1 +
arch/x86/kvm/emulate.c | 8 ++++++++
arch/x86/kvm/x86.c | 1 +
arch/x86/kvm/x86.h | 5 +++++
4 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 6040d11..049a6f5 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -244,6 +244,7 @@ struct x86_emulate_ctxt {
bool guest_mode; /* guest running a nested guest */
bool perm_ok; /* do not check permissions if true */
bool only_vendor_specific_insn;
+ bool page_table_written_insn;

bool have_exception;
struct x86_exception exception;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 0453c07..3c027ac 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2516,6 +2516,7 @@ static int em_add(struct x86_emulate_ctxt *ctxt)
static int em_or(struct x86_emulate_ctxt *ctxt)
{
emulate_2op_SrcV("or", ctxt->src, ctxt->dst, ctxt->eflags);
+ tag_page_table_written_insn(ctxt);
return X86EMUL_CONTINUE;
}

@@ -2534,6 +2535,7 @@ static int em_sbb(struct x86_emulate_ctxt *ctxt)
static int em_and(struct x86_emulate_ctxt *ctxt)
{
emulate_2op_SrcV("and", ctxt->src, ctxt->dst, ctxt->eflags);
+ tag_page_table_written_insn(ctxt);
return X86EMUL_CONTINUE;
}

@@ -2572,6 +2574,7 @@ static int em_xchg(struct x86_emulate_ctxt *ctxt)
/* Write back the memory destination with implicit LOCK prefix. */
ctxt->dst.val = ctxt->src.orig_val;
ctxt->lock_prefix = 1;
+ tag_page_table_written_insn(ctxt);
return X86EMUL_CONTINUE;
}

@@ -2610,6 +2613,7 @@ static int em_rdtsc(struct x86_emulate_ctxt *ctxt)
static int em_mov(struct x86_emulate_ctxt *ctxt)
{
ctxt->dst.val = ctxt->src.val;
+ tag_page_table_written_insn(ctxt);
return X86EMUL_CONTINUE;
}

@@ -4135,6 +4139,7 @@ twobyte_insn:
break;
case 0xab:
bts: /* bts */
+ tag_page_table_written_insn(ctxt);
emulate_2op_SrcV_nobyte("bts", ctxt->src, ctxt->dst, ctxt->eflags);
break;
case 0xac: /* shrd imm8, r, r/m */
@@ -4148,6 +4153,7 @@ twobyte_insn:
* Save real source value, then compare EAX against
* destination.
*/
+ tag_page_table_written_insn(ctxt);
ctxt->src.orig_val = ctxt->src.val;
ctxt->src.val = ctxt->regs[VCPU_REGS_RAX];
emulate_2op_SrcV("cmp", ctxt->src, ctxt->dst, ctxt->eflags);
@@ -4192,6 +4198,7 @@ twobyte_insn:
break;
case 0xbb:
btc: /* btc */
+ tag_page_table_written_insn(ctxt);
emulate_2op_SrcV_nobyte("btc", ctxt->src, ctxt->dst, ctxt->eflags);
break;
case 0xbc: { /* bsf */
@@ -4235,6 +4242,7 @@ twobyte_insn:
(u64) ctxt->src.val;
break;
case 0xc7: /* Grp9 (cmpxchg8b) */
+ tag_page_table_written_insn(ctxt);
rc = em_grp9(ctxt);
break;
default:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ea8f9f0..cf6fb29 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4831,6 +4831,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
ctxt->interruptibility = 0;
ctxt->have_exception = false;
ctxt->perm_ok = false;
+ ctxt->page_table_written_insn = false;

ctxt->only_vendor_specific_insn
= emulation_type & EMULTYPE_TRAP_UD;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index d36fe23..b6e868f 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -111,6 +111,11 @@ static inline bool vcpu_match_mmio_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
return false;
}

+static inline void tag_page_table_written_insn(struct x86_emulate_ctxt *ctxt)
+{
+ ctxt->page_table_written_insn = true;
+}
+
void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
--
1.7.5.4