* [PATCH 1/3] KVM: x86: Add EMULTYPE_PF when emulation is triggered by a page fault
2019-11-22 22:58 [PATCH 0/3] KVM: x86: Minor emulator cleanup Sean Christopherson
@ 2019-11-22 22:58 ` Sean Christopherson
2019-11-22 22:58 ` [PATCH 2/3] KVM: x86: Move gpa_val and gpa_available into the emulator context Sean Christopherson
2019-11-22 22:58 ` [PATCH 3/3] KVM: x86: Move #PF retry tracking variables into emulation context Sean Christopherson
2 siblings, 0 replies; 4+ messages in thread
From: Sean Christopherson @ 2019-11-22 22:58 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, linux-kernel
Add a new emulation type flag to explicitly mark emulation related to a
page fault. Use the new flag, EMULTYPE_PF, to move the propagation of
the GPA into the emulator context from the page fault handler into
x86_emulate_instruction.
Similarly, to help clarify how cr2 is used, don't propagate cr2 into the
exception.address when it's *not* valid and instead explicitly zero out
exception.address. Functionally this is a nop, as all non-EMULTYPE_PF
callers pass zero for cr2, i.e. it's effectively a documentation update.
Zeroing exception.address is probably unnecessary as it shouldn't be
exposed to the guest for non-#PF exceptions, but keep the current
behavior to avoid introducing an unintentional function change.
Append _PF to EMULTYPE_ALLOW_RETRY to make it clear retrying is only
intended for use when emulating after a #PF, and add WARNs to enforce
that notion.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_host.h | 12 +++++++++---
arch/x86/kvm/mmu/mmu.c | 10 ++--------
arch/x86/kvm/x86.c | 25 +++++++++++++++++++------
3 files changed, 30 insertions(+), 17 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b79cd6aa4075..6311fffbc2f0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1347,8 +1347,9 @@ extern u64 kvm_mce_cap_supported;
* decode the instruction length. For use *only* by
* kvm_x86_ops->skip_emulated_instruction() implementations.
*
- * EMULTYPE_ALLOW_RETRY - Set when the emulator should resume the guest to
- * retry native execution under certain conditions.
+ * EMULTYPE_ALLOW_RETRY_PF - Set when the emulator should resume the guest to
+ * retry native execution under certain conditions,
+ * Can only be set in conjunction with EMULTYPE_PF.
*
* EMULTYPE_TRAP_UD_FORCED - Set when emulating an intercepted #UD that was
* triggered by KVM's magic "force emulation" prefix,
@@ -1361,13 +1362,18 @@ extern u64 kvm_mce_cap_supported;
* backdoor emulation, which is opt in via module param.
* VMware backoor emulation handles select instructions
* and reinjects the #GP for all other cases.
+ *
+ * EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in which
+ * case the CR2/GPA value pass on the stack is valid.
*/
#define EMULTYPE_NO_DECODE (1 << 0)
#define EMULTYPE_TRAP_UD (1 << 1)
#define EMULTYPE_SKIP (1 << 2)
-#define EMULTYPE_ALLOW_RETRY (1 << 3)
+#define EMULTYPE_ALLOW_RETRY_PF (1 << 3)
#define EMULTYPE_TRAP_UD_FORCED (1 << 4)
#define EMULTYPE_VMWARE_GP (1 << 5)
+#define EMULTYPE_PF (1 << 6)
+
int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type);
int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu,
void *insn, int insn_len);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 6f92b40d798c..fa49d9971b59 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5519,15 +5519,9 @@ static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
void *insn, int insn_len)
{
- int r, emulation_type = 0;
+ int r, emulation_type = EMULTYPE_PF;
bool direct = vcpu->arch.mmu->direct_map;
- /* With shadow page tables, fault_address contains a GVA or nGPA. */
- if (vcpu->arch.mmu->direct_map) {
- vcpu->arch.gpa_available = true;
- vcpu->arch.gpa_val = cr2;
- }
-
r = RET_PF_INVALID;
if (unlikely(error_code & PFERR_RSVD_MASK)) {
r = handle_mmio_page_fault(vcpu, cr2, direct);
@@ -5572,7 +5566,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
* for L1 isn't going to magically fix whatever issue cause L2 to fail.
*/
if (!mmio_info_in_cache(vcpu, cr2, direct) && !is_guest_mode(vcpu))
- emulation_type = EMULTYPE_ALLOW_RETRY;
+ emulation_type |= EMULTYPE_ALLOW_RETRY_PF;
emulate:
/*
* On AMD platforms, under certain conditions insn_len may be zero on #NPF.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a256e09f321a..848e4ec21c5e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6393,10 +6393,11 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t cr2,
gpa_t gpa = cr2;
kvm_pfn_t pfn;
- if (!(emulation_type & EMULTYPE_ALLOW_RETRY))
+ if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF))
return false;
- if (WARN_ON_ONCE(is_guest_mode(vcpu)))
+ if (WARN_ON_ONCE(is_guest_mode(vcpu)) ||
+ WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF)))
return false;
if (!vcpu->arch.mmu->direct_map) {
@@ -6484,10 +6485,11 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
*/
vcpu->arch.last_retry_eip = vcpu->arch.last_retry_addr = 0;
- if (!(emulation_type & EMULTYPE_ALLOW_RETRY))
+ if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF))
return false;
- if (WARN_ON_ONCE(is_guest_mode(vcpu)))
+ if (WARN_ON_ONCE(is_guest_mode(vcpu)) ||
+ WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF)))
return false;
if (x86_page_table_writing_insn(ctxt))
@@ -6742,8 +6744,19 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
}
restart:
- /* Save the faulting GPA (cr2) in the address field */
- ctxt->exception.address = cr2;
+ if (emulation_type & EMULTYPE_PF) {
+ /* Save the faulting GPA (cr2) in the address field */
+ ctxt->exception.address = cr2;
+
+ /* With shadow page tables, cr2 contains a GVA or nGPA. */
+ if (vcpu->arch.mmu->direct_map) {
+ vcpu->arch.gpa_available = true;
+ vcpu->arch.gpa_val = cr2;
+ }
+ } else {
+ /* Sanitize the address out of an abundance of paranoia. */
+ ctxt->exception.address = 0;
+ }
r = x86_emulate_insn(ctxt);
--
2.24.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 2/3] KVM: x86: Move gpa_val and gpa_available into the emulator context
2019-11-22 22:58 [PATCH 0/3] KVM: x86: Minor emulator cleanup Sean Christopherson
2019-11-22 22:58 ` [PATCH 1/3] KVM: x86: Add EMULTYPE_PF when emulation is triggered by a page fault Sean Christopherson
@ 2019-11-22 22:58 ` Sean Christopherson
2019-11-22 22:58 ` [PATCH 3/3] KVM: x86: Move #PF retry tracking variables into emulation context Sean Christopherson
2 siblings, 0 replies; 4+ messages in thread
From: Sean Christopherson @ 2019-11-22 22:58 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, linux-kernel
Move the GPA tracking into the emulator context to prevent it from being
abused in the standard page fault flow. All paths into the emulator go
through init_emulate_ctxt(), so there's no need to clear gpa_available
after every VM-Exit. The only partial exception is EMULTYPE_NO_DECODE,
but in that case the emulator is simply being re-entered, i.e. retaining
gpa_available is correct and consistent with current behavior.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_emulate.h | 4 ++++
arch/x86/include/asm/kvm_host.h | 4 ----
arch/x86/kvm/x86.c | 13 ++++++-------
3 files changed, 10 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 77cf6c11f66b..e81658a4ab9d 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -307,6 +307,10 @@ struct x86_emulate_ctxt {
bool have_exception;
struct x86_exception exception;
+ /* GPA available */
+ bool gpa_available;
+ gpa_t gpa_val;
+
/*
* decode cache
*/
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6311fffbc2f0..e434f4cfecd1 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -791,10 +791,6 @@ struct kvm_vcpu_arch {
int pending_ioapic_eoi;
int pending_external_vector;
- /* GPA available */
- bool gpa_available;
- gpa_t gpa_val;
-
/* be preempted when it's in kernel-mode(cpl=0) */
bool preempted_in_kernel;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 848e4ec21c5e..9a8adfdf1e0a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5664,10 +5664,9 @@ static int emulator_read_write_onepage(unsigned long addr, void *val,
* operation using rep will only have the initial GPA from the NPF
* occurred.
*/
- if (vcpu->arch.gpa_available &&
- emulator_can_use_gpa(ctxt) &&
- (addr & ~PAGE_MASK) == (vcpu->arch.gpa_val & ~PAGE_MASK)) {
- gpa = vcpu->arch.gpa_val;
+ if (ctxt->gpa_available && emulator_can_use_gpa(ctxt) &&
+ (addr & ~PAGE_MASK) == (ctxt->gpa_val & ~PAGE_MASK)) {
+ gpa = ctxt->gpa_val;
ret = vcpu_is_mmio_gpa(vcpu, addr, gpa, write);
} else {
ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write);
@@ -6318,6 +6317,7 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
+ ctxt->gpa_available = false;
ctxt->eflags = kvm_get_rflags(vcpu);
ctxt->tf = (ctxt->eflags & X86_EFLAGS_TF) != 0;
@@ -6750,8 +6750,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
/* With shadow page tables, cr2 contains a GVA or nGPA. */
if (vcpu->arch.mmu->direct_map) {
- vcpu->arch.gpa_available = true;
- vcpu->arch.gpa_val = cr2;
+ ctxt->gpa_available = true;
+ ctxt->gpa_val = cr2;
}
} else {
/* Sanitize the address out of an abundance of paranoia. */
@@ -8306,7 +8306,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (vcpu->arch.apic_attention)
kvm_lapic_sync_from_vapic(vcpu);
- vcpu->arch.gpa_available = false;
r = kvm_x86_ops->handle_exit(vcpu);
return r;
--
2.24.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 3/3] KVM: x86: Move #PF retry tracking variables into emulation context
2019-11-22 22:58 [PATCH 0/3] KVM: x86: Minor emulator cleanup Sean Christopherson
2019-11-22 22:58 ` [PATCH 1/3] KVM: x86: Add EMULTYPE_PF when emulation is triggered by a page fault Sean Christopherson
2019-11-22 22:58 ` [PATCH 2/3] KVM: x86: Move gpa_val and gpa_available into the emulator context Sean Christopherson
@ 2019-11-22 22:58 ` Sean Christopherson
2 siblings, 0 replies; 4+ messages in thread
From: Sean Christopherson @ 2019-11-22 22:58 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, linux-kernel
Move last_retry_eip and last_retry_addr into the emulation context as
they are specific to retrying an instruction after emulation failure.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_emulate.h | 4 ++++
arch/x86/include/asm/kvm_host.h | 3 ---
arch/x86/kvm/x86.c | 11 ++++++-----
3 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index e81658a4ab9d..9c5db3b4120e 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -311,6 +311,10 @@ struct x86_emulate_ctxt {
bool gpa_available;
gpa_t gpa_val;
+ /* Track EIP and CR2/GPA when retrying faulting instruction on #PF. */
+ unsigned long last_retry_eip;
+ unsigned long last_retry_addr;
+
/*
* decode cache
*/
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e434f4cfecd1..6c8bfebabc31 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -745,9 +745,6 @@ struct kvm_vcpu_arch {
cpumask_var_t wbinvd_dirty_mask;
- unsigned long last_retry_eip;
- unsigned long last_retry_addr;
-
struct {
bool halted;
gfn_t gfns[roundup_pow_of_two(ASYNC_PF_PER_VCPU)];
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a8adfdf1e0a..3aa2d7d98779 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6317,6 +6317,7 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
+ /* last_retry_{eip,addr} are persistent and must not be init'd here. */
ctxt->gpa_available = false;
ctxt->eflags = kvm_get_rflags(vcpu);
ctxt->tf = (ctxt->eflags & X86_EFLAGS_TF) != 0;
@@ -6467,8 +6468,8 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
unsigned long last_retry_eip, last_retry_addr, gpa = cr2;
- last_retry_eip = vcpu->arch.last_retry_eip;
- last_retry_addr = vcpu->arch.last_retry_addr;
+ last_retry_eip = ctxt->last_retry_eip;
+ last_retry_addr = ctxt->last_retry_addr;
/*
* If the emulation is caused by #PF and it is non-page_table
@@ -6483,7 +6484,7 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
* and the address again, we can break out of the potential infinite
* loop.
*/
- vcpu->arch.last_retry_eip = vcpu->arch.last_retry_addr = 0;
+ ctxt->last_retry_eip = ctxt->last_retry_addr = 0;
if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF))
return false;
@@ -6498,8 +6499,8 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
if (ctxt->eip == last_retry_eip && last_retry_addr == cr2)
return false;
- vcpu->arch.last_retry_eip = ctxt->eip;
- vcpu->arch.last_retry_addr = cr2;
+ ctxt->last_retry_eip = ctxt->eip;
+ ctxt->last_retry_addr = cr2;
if (!vcpu->arch.mmu->direct_map)
gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2, NULL);
--
2.24.0
^ permalink raw reply related [flat|nested] 4+ messages in thread