* [GIT PULL 1/3] arm/arm64: KVM: Use set/way op trapping to track the state of the caches
2015-01-29 22:37 [GIT PULL 0/3] Second round of KVM/ARM fixes for 3.19 Christoffer Dall
@ 2015-01-29 22:37 ` Christoffer Dall
2015-01-29 22:37 ` [GIT PULL 2/3] arm/arm64: KVM: Invalidate data cache on unmap Christoffer Dall
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Christoffer Dall @ 2015-01-29 22:37 UTC (permalink / raw)
To: linux-arm-kernel
From: Marc Zyngier <marc.zyngier@arm.com>
Trying to emulate the behaviour of set/way cache ops is fairly
pointless, as there are too many ways we can end-up missing stuff.
Also, there is some system caches out there that simply ignore
set/way operations.
So instead of trying to implement them, let's convert it to VA ops,
and use them as a way to re-enable the trapping of VM ops. That way,
we can detect the point when the MMU/caches are turned off, and do
a full VM flush (which is what the guest was trying to do anyway).
This allows a 32bit zImage to boot on the APM thingy, and will
probably help bootloaders in general.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
arch/arm/include/asm/kvm_emulate.h | 10 +++++
arch/arm/include/asm/kvm_host.h | 3 --
arch/arm/include/asm/kvm_mmu.h | 3 +-
arch/arm/kvm/arm.c | 10 -----
arch/arm/kvm/coproc.c | 70 +++++++--------------------------
arch/arm/kvm/coproc.h | 6 +--
arch/arm/kvm/coproc_a15.c | 2 +-
arch/arm/kvm/coproc_a7.c | 2 +-
arch/arm/kvm/mmu.c | 70 ++++++++++++++++++++++++++++++++-
arch/arm/kvm/trace.h | 39 +++++++++++++++++++
arch/arm64/include/asm/kvm_emulate.h | 10 +++++
arch/arm64/include/asm/kvm_host.h | 3 --
arch/arm64/include/asm/kvm_mmu.h | 3 +-
arch/arm64/kvm/sys_regs.c | 75 +++++-------------------------------
14 files changed, 161 insertions(+), 145 deletions(-)
diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
index 66ce176..7b01523 100644
--- a/arch/arm/include/asm/kvm_emulate.h
+++ b/arch/arm/include/asm/kvm_emulate.h
@@ -38,6 +38,16 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
vcpu->arch.hcr = HCR_GUEST_MASK;
}
+static inline unsigned long vcpu_get_hcr(struct kvm_vcpu *vcpu)
+{
+ return vcpu->arch.hcr;
+}
+
+static inline void vcpu_set_hcr(struct kvm_vcpu *vcpu, unsigned long hcr)
+{
+ vcpu->arch.hcr = hcr;
+}
+
static inline bool vcpu_mode_is_32bit(struct kvm_vcpu *vcpu)
{
return 1;
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 254e065..04b4ea0 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -125,9 +125,6 @@ struct kvm_vcpu_arch {
* Anything that is not used directly from assembly code goes
* here.
*/
- /* dcache set/way operation pending */
- int last_pcpu;
- cpumask_t require_dcache_flush;
/* Don't run the guest on this vcpu */
bool pause;
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 63e0ecc..286644c 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -190,7 +190,8 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
#define kvm_virt_to_phys(x) virt_to_idmap((unsigned long)(x))
-void stage2_flush_vm(struct kvm *kvm);
+void kvm_set_way_flush(struct kvm_vcpu *vcpu);
+void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled);
#endif /* !__ASSEMBLY__ */
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 2d6d910..0b0d58a 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -281,15 +281,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
vcpu->cpu = cpu;
vcpu->arch.host_cpu_context = this_cpu_ptr(kvm_host_cpu_state);
- /*
- * Check whether this vcpu requires the cache to be flushed on
- * this physical CPU. This is a consequence of doing dcache
- * operations by set/way on this vcpu. We do it here to be in
- * a non-preemptible section.
- */
- if (cpumask_test_and_clear_cpu(cpu, &vcpu->arch.require_dcache_flush))
- flush_cache_all(); /* We'd really want v7_flush_dcache_all() */
-
kvm_arm_set_running_vcpu(vcpu);
}
@@ -541,7 +532,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
vcpu->mode = OUTSIDE_GUEST_MODE;
- vcpu->arch.last_pcpu = smp_processor_id();
kvm_guest_exit();
trace_kvm_exit(*vcpu_pc(vcpu));
/*
diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
index 7928dbd..f3d88dc 100644
--- a/arch/arm/kvm/coproc.c
+++ b/arch/arm/kvm/coproc.c
@@ -189,82 +189,40 @@ static bool access_l2ectlr(struct kvm_vcpu *vcpu,
return true;
}
-/* See note at ARM ARM B1.14.4 */
+/*
+ * See note at ARMv7 ARM B1.14.4 (TL;DR: S/W ops are not easily virtualized).
+ */
static bool access_dcsw(struct kvm_vcpu *vcpu,
const struct coproc_params *p,
const struct coproc_reg *r)
{
- unsigned long val;
- int cpu;
-
if (!p->is_write)
return read_from_write_only(vcpu, p);
- cpu = get_cpu();
-
- cpumask_setall(&vcpu->arch.require_dcache_flush);
- cpumask_clear_cpu(cpu, &vcpu->arch.require_dcache_flush);
-
- /* If we were already preempted, take the long way around */
- if (cpu != vcpu->arch.last_pcpu) {
- flush_cache_all();
- goto done;
- }
-
- val = *vcpu_reg(vcpu, p->Rt1);
-
- switch (p->CRm) {
- case 6: /* Upgrade DCISW to DCCISW, as per HCR.SWIO */
- case 14: /* DCCISW */
- asm volatile("mcr p15, 0, %0, c7, c14, 2" : : "r" (val));
- break;
-
- case 10: /* DCCSW */
- asm volatile("mcr p15, 0, %0, c7, c10, 2" : : "r" (val));
- break;
- }
-
-done:
- put_cpu();
-
+ kvm_set_way_flush(vcpu);
return true;
}
/*
* Generic accessor for VM registers. Only called as long as HCR_TVM
- * is set.
+ * is set. If the guest enables the MMU, we stop trapping the VM
+ * sys_regs and leave it in complete control of the caches.
+ *
+ * Used by the cpu-specific code.
*/
-static bool access_vm_reg(struct kvm_vcpu *vcpu,
- const struct coproc_params *p,
- const struct coproc_reg *r)
+bool access_vm_reg(struct kvm_vcpu *vcpu,
+ const struct coproc_params *p,
+ const struct coproc_reg *r)
{
+ bool was_enabled = vcpu_has_cache_enabled(vcpu);
+
BUG_ON(!p->is_write);
vcpu->arch.cp15[r->reg] = *vcpu_reg(vcpu, p->Rt1);
if (p->is_64bit)
vcpu->arch.cp15[r->reg + 1] = *vcpu_reg(vcpu, p->Rt2);
- return true;
-}
-
-/*
- * SCTLR accessor. Only called as long as HCR_TVM is set. If the
- * guest enables the MMU, we stop trapping the VM sys_regs and leave
- * it in complete control of the caches.
- *
- * Used by the cpu-specific code.
- */
-bool access_sctlr(struct kvm_vcpu *vcpu,
- const struct coproc_params *p,
- const struct coproc_reg *r)
-{
- access_vm_reg(vcpu, p, r);
-
- if (vcpu_has_cache_enabled(vcpu)) { /* MMU+Caches enabled? */
- vcpu->arch.hcr &= ~HCR_TVM;
- stage2_flush_vm(vcpu->kvm);
- }
-
+ kvm_toggle_cache(vcpu, was_enabled);
return true;
}
diff --git a/arch/arm/kvm/coproc.h b/arch/arm/kvm/coproc.h
index 1a44bbe..88d24a3 100644
--- a/arch/arm/kvm/coproc.h
+++ b/arch/arm/kvm/coproc.h
@@ -153,8 +153,8 @@ static inline int cmp_reg(const struct coproc_reg *i1,
#define is64 .is_64 = true
#define is32 .is_64 = false
-bool access_sctlr(struct kvm_vcpu *vcpu,
- const struct coproc_params *p,
- const struct coproc_reg *r);
+bool access_vm_reg(struct kvm_vcpu *vcpu,
+ const struct coproc_params *p,
+ const struct coproc_reg *r);
#endif /* __ARM_KVM_COPROC_LOCAL_H__ */
diff --git a/arch/arm/kvm/coproc_a15.c b/arch/arm/kvm/coproc_a15.c
index e6f4ae4..a713675 100644
--- a/arch/arm/kvm/coproc_a15.c
+++ b/arch/arm/kvm/coproc_a15.c
@@ -34,7 +34,7 @@
static const struct coproc_reg a15_regs[] = {
/* SCTLR: swapped by interrupt.S. */
{ CRn( 1), CRm( 0), Op1( 0), Op2( 0), is32,
- access_sctlr, reset_val, c1_SCTLR, 0x00C50078 },
+ access_vm_reg, reset_val, c1_SCTLR, 0x00C50078 },
};
static struct kvm_coproc_target_table a15_target_table = {
diff --git a/arch/arm/kvm/coproc_a7.c b/arch/arm/kvm/coproc_a7.c
index 17fc7cd..b19e46d 100644
--- a/arch/arm/kvm/coproc_a7.c
+++ b/arch/arm/kvm/coproc_a7.c
@@ -37,7 +37,7 @@
static const struct coproc_reg a7_regs[] = {
/* SCTLR: swapped by interrupt.S. */
{ CRn( 1), CRm( 0), Op1( 0), Op2( 0), is32,
- access_sctlr, reset_val, c1_SCTLR, 0x00C50878 },
+ access_vm_reg, reset_val, c1_SCTLR, 0x00C50878 },
};
static struct kvm_coproc_target_table a7_target_table = {
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 1dc9778..106737e 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -278,7 +278,7 @@ static void stage2_flush_memslot(struct kvm *kvm,
* Go through the stage 2 page tables and invalidate any cache lines
* backing memory already mapped to the VM.
*/
-void stage2_flush_vm(struct kvm *kvm)
+static void stage2_flush_vm(struct kvm *kvm)
{
struct kvm_memslots *slots;
struct kvm_memory_slot *memslot;
@@ -1411,3 +1411,71 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
unmap_stage2_range(kvm, gpa, size);
spin_unlock(&kvm->mmu_lock);
}
+
+/*
+ * See note at ARMv7 ARM B1.14.4 (TL;DR: S/W ops are not easily virtualized).
+ *
+ * Main problems:
+ * - S/W ops are local to a CPU (not broadcast)
+ * - We have line migration behind our back (speculation)
+ * - System caches don't support S/W at all (damn!)
+ *
+ * In the face of the above, the best we can do is to try and convert
+ * S/W ops to VA ops. Because the guest is not allowed to infer the
+ * S/W to PA mapping, it can only use S/W to nuke the whole cache,
+ * which is a rather good thing for us.
+ *
+ * Also, it is only used when turning caches on/off ("The expected
+ * usage of the cache maintenance instructions that operate by set/way
+ * is associated with the cache maintenance instructions associated
+ * with the powerdown and powerup of caches, if this is required by
+ * the implementation.").
+ *
+ * We use the following policy:
+ *
+ * - If we trap a S/W operation, we enable VM trapping to detect
+ * caches being turned on/off, and do a full clean.
+ *
+ * - We flush the caches on both caches being turned on and off.
+ *
+ * - Once the caches are enabled, we stop trapping VM ops.
+ */
+void kvm_set_way_flush(struct kvm_vcpu *vcpu)
+{
+ unsigned long hcr = vcpu_get_hcr(vcpu);
+
+ /*
+ * If this is the first time we do a S/W operation
+ * (i.e. HCR_TVM not set) flush the whole memory, and set the
+ * VM trapping.
+ *
+ * Otherwise, rely on the VM trapping to wait for the MMU +
+ * Caches to be turned off. At that point, we'll be able to
+ * clean the caches again.
+ */
+ if (!(hcr & HCR_TVM)) {
+ trace_kvm_set_way_flush(*vcpu_pc(vcpu),
+ vcpu_has_cache_enabled(vcpu));
+ stage2_flush_vm(vcpu->kvm);
+ vcpu_set_hcr(vcpu, hcr | HCR_TVM);
+ }
+}
+
+void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled)
+{
+ bool now_enabled = vcpu_has_cache_enabled(vcpu);
+
+ /*
+ * If switching the MMU+caches on, need to invalidate the caches.
+ * If switching it off, need to clean the caches.
+ * Clean + invalidate does the trick always.
+ */
+ if (now_enabled != was_enabled)
+ stage2_flush_vm(vcpu->kvm);
+
+ /* Caches are now on, stop trapping VM ops (until a S/W op) */
+ if (now_enabled)
+ vcpu_set_hcr(vcpu, vcpu_get_hcr(vcpu) & ~HCR_TVM);
+
+ trace_kvm_toggle_cache(*vcpu_pc(vcpu), was_enabled, now_enabled);
+}
diff --git a/arch/arm/kvm/trace.h b/arch/arm/kvm/trace.h
index b1d640f..b6a6e71 100644
--- a/arch/arm/kvm/trace.h
+++ b/arch/arm/kvm/trace.h
@@ -223,6 +223,45 @@ TRACE_EVENT(kvm_hvc,
__entry->vcpu_pc, __entry->r0, __entry->imm)
);
+TRACE_EVENT(kvm_set_way_flush,
+ TP_PROTO(unsigned long vcpu_pc, bool cache),
+ TP_ARGS(vcpu_pc, cache),
+
+ TP_STRUCT__entry(
+ __field( unsigned long, vcpu_pc )
+ __field( bool, cache )
+ ),
+
+ TP_fast_assign(
+ __entry->vcpu_pc = vcpu_pc;
+ __entry->cache = cache;
+ ),
+
+ TP_printk("S/W flush at 0x%016lx (cache %s)",
+ __entry->vcpu_pc, __entry->cache ? "on" : "off")
+);
+
+TRACE_EVENT(kvm_toggle_cache,
+ TP_PROTO(unsigned long vcpu_pc, bool was, bool now),
+ TP_ARGS(vcpu_pc, was, now),
+
+ TP_STRUCT__entry(
+ __field( unsigned long, vcpu_pc )
+ __field( bool, was )
+ __field( bool, now )
+ ),
+
+ TP_fast_assign(
+ __entry->vcpu_pc = vcpu_pc;
+ __entry->was = was;
+ __entry->now = now;
+ ),
+
+ TP_printk("VM op at 0x%016lx (cache was %s, now %s)",
+ __entry->vcpu_pc, __entry->was ? "on" : "off",
+ __entry->now ? "on" : "off")
+);
+
#endif /* _TRACE_KVM_H */
#undef TRACE_INCLUDE_PATH
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 865a7e2..3cb4c85 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -45,6 +45,16 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
vcpu->arch.hcr_el2 &= ~HCR_RW;
}
+static inline unsigned long vcpu_get_hcr(struct kvm_vcpu *vcpu)
+{
+ return vcpu->arch.hcr_el2;
+}
+
+static inline void vcpu_set_hcr(struct kvm_vcpu *vcpu, unsigned long hcr)
+{
+ vcpu->arch.hcr_el2 = hcr;
+}
+
static inline unsigned long *vcpu_pc(const struct kvm_vcpu *vcpu)
{
return (unsigned long *)&vcpu_gp_regs(vcpu)->regs.pc;
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 0b7dfdb..acd101a 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -116,9 +116,6 @@ struct kvm_vcpu_arch {
* Anything that is not used directly from assembly code goes
* here.
*/
- /* dcache set/way operation pending */
- int last_pcpu;
- cpumask_t require_dcache_flush;
/* Don't run the guest */
bool pause;
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 14a74f1..92d22e9 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -260,7 +260,8 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
#define kvm_virt_to_phys(x) __virt_to_phys((unsigned long)(x))
-void stage2_flush_vm(struct kvm *kvm);
+void kvm_set_way_flush(struct kvm_vcpu *vcpu);
+void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled);
#endif /* __ASSEMBLY__ */
#endif /* __ARM64_KVM_MMU_H__ */
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3d7c2df..f31e8bb 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -69,68 +69,31 @@ static u32 get_ccsidr(u32 csselr)
return ccsidr;
}
-static void do_dc_cisw(u32 val)
-{
- asm volatile("dc cisw, %x0" : : "r" (val));
- dsb(ish);
-}
-
-static void do_dc_csw(u32 val)
-{
- asm volatile("dc csw, %x0" : : "r" (val));
- dsb(ish);
-}
-
-/* See note at ARM ARM B1.14.4 */
+/*
+ * See note at ARMv7 ARM B1.14.4 (TL;DR: S/W ops are not easily virtualized).
+ */
static bool access_dcsw(struct kvm_vcpu *vcpu,
const struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
- unsigned long val;
- int cpu;
-
if (!p->is_write)
return read_from_write_only(vcpu, p);
- cpu = get_cpu();
-
- cpumask_setall(&vcpu->arch.require_dcache_flush);
- cpumask_clear_cpu(cpu, &vcpu->arch.require_dcache_flush);
-
- /* If we were already preempted, take the long way around */
- if (cpu != vcpu->arch.last_pcpu) {
- flush_cache_all();
- goto done;
- }
-
- val = *vcpu_reg(vcpu, p->Rt);
-
- switch (p->CRm) {
- case 6: /* Upgrade DCISW to DCCISW, as per HCR.SWIO */
- case 14: /* DCCISW */
- do_dc_cisw(val);
- break;
-
- case 10: /* DCCSW */
- do_dc_csw(val);
- break;
- }
-
-done:
- put_cpu();
-
+ kvm_set_way_flush(vcpu);
return true;
}
/*
* Generic accessor for VM registers. Only called as long as HCR_TVM
- * is set.
+ * is set. If the guest enables the MMU, we stop trapping the VM
+ * sys_regs and leave it in complete control of the caches.
*/
static bool access_vm_reg(struct kvm_vcpu *vcpu,
const struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
unsigned long val;
+ bool was_enabled = vcpu_has_cache_enabled(vcpu);
BUG_ON(!p->is_write);
@@ -143,25 +106,7 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu,
vcpu_cp15_64_low(vcpu, r->reg) = val & 0xffffffffUL;
}
- return true;
-}
-
-/*
- * SCTLR_EL1 accessor. Only called as long as HCR_TVM is set. If the
- * guest enables the MMU, we stop trapping the VM sys_regs and leave
- * it in complete control of the caches.
- */
-static bool access_sctlr(struct kvm_vcpu *vcpu,
- const struct sys_reg_params *p,
- const struct sys_reg_desc *r)
-{
- access_vm_reg(vcpu, p, r);
-
- if (vcpu_has_cache_enabled(vcpu)) { /* MMU+Caches enabled? */
- vcpu->arch.hcr_el2 &= ~HCR_TVM;
- stage2_flush_vm(vcpu->kvm);
- }
-
+ kvm_toggle_cache(vcpu, was_enabled);
return true;
}
@@ -377,7 +322,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
NULL, reset_mpidr, MPIDR_EL1 },
/* SCTLR_EL1 */
{ Op0(0b11), Op1(0b000), CRn(0b0001), CRm(0b0000), Op2(0b000),
- access_sctlr, reset_val, SCTLR_EL1, 0x00C50078 },
+ access_vm_reg, reset_val, SCTLR_EL1, 0x00C50078 },
/* CPACR_EL1 */
{ Op0(0b11), Op1(0b000), CRn(0b0001), CRm(0b0000), Op2(0b010),
NULL, reset_val, CPACR_EL1, 0 },
@@ -657,7 +602,7 @@ static const struct sys_reg_desc cp14_64_regs[] = {
* register).
*/
static const struct sys_reg_desc cp15_regs[] = {
- { Op1( 0), CRn( 1), CRm( 0), Op2( 0), access_sctlr, NULL, c1_SCTLR },
+ { Op1( 0), CRn( 1), CRm( 0), Op2( 0), access_vm_reg, NULL, c1_SCTLR },
{ Op1( 0), CRn( 2), CRm( 0), Op2( 0), access_vm_reg, NULL, c2_TTBR0 },
{ Op1( 0), CRn( 2), CRm( 0), Op2( 1), access_vm_reg, NULL, c2_TTBR1 },
{ Op1( 0), CRn( 2), CRm( 0), Op2( 2), access_vm_reg, NULL, c2_TTBCR },
--
2.1.2.330.g565301e.dirty
^ permalink raw reply related [flat|nested] 5+ messages in thread* [GIT PULL 2/3] arm/arm64: KVM: Invalidate data cache on unmap
2015-01-29 22:37 [GIT PULL 0/3] Second round of KVM/ARM fixes for 3.19 Christoffer Dall
2015-01-29 22:37 ` [GIT PULL 1/3] arm/arm64: KVM: Use set/way op trapping to track the state of the caches Christoffer Dall
@ 2015-01-29 22:37 ` Christoffer Dall
2015-01-29 22:37 ` [GIT PULL 3/3] arm/arm64: KVM: Use kernel mapping to perform invalidation on page fault Christoffer Dall
2015-01-30 11:30 ` [GIT PULL 0/3] Second round of KVM/ARM fixes for 3.19 Paolo Bonzini
3 siblings, 0 replies; 5+ messages in thread
From: Christoffer Dall @ 2015-01-29 22:37 UTC (permalink / raw)
To: linux-arm-kernel
From: Marc Zyngier <marc.zyngier@arm.com>
Let's assume a guest has created an uncached mapping, and written
to that page. Let's also assume that the host uses a cache-coherent
IO subsystem. Let's finally assume that the host is under memory
pressure and starts to swap things out.
Before this "uncached" page is evicted, we need to make sure
we invalidate potential speculated, clean cache lines that are
sitting there, or the IO subsystem is going to swap out the
cached view, loosing the data that has been written directly
into memory.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
arch/arm/include/asm/kvm_mmu.h | 31 +++++++++++++++
arch/arm/kvm/mmu.c | 82 ++++++++++++++++++++++++++++++++--------
arch/arm64/include/asm/kvm_mmu.h | 18 +++++++++
3 files changed, 116 insertions(+), 15 deletions(-)
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 286644c..552c31f 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -44,6 +44,7 @@
#ifndef __ASSEMBLY__
+#include <linux/highmem.h>
#include <asm/cacheflush.h>
#include <asm/pgalloc.h>
@@ -188,6 +189,36 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
}
}
+static inline void __kvm_flush_dcache_pte(pte_t pte)
+{
+ void *va = kmap_atomic(pte_page(pte));
+
+ kvm_flush_dcache_to_poc(va, PAGE_SIZE);
+
+ kunmap_atomic(va);
+}
+
+static inline void __kvm_flush_dcache_pmd(pmd_t pmd)
+{
+ unsigned long size = PMD_SIZE;
+ pfn_t pfn = pmd_pfn(pmd);
+
+ while (size) {
+ void *va = kmap_atomic_pfn(pfn);
+
+ kvm_flush_dcache_to_poc(va, PAGE_SIZE);
+
+ pfn++;
+ size -= PAGE_SIZE;
+
+ kunmap_atomic(va);
+ }
+}
+
+static inline void __kvm_flush_dcache_pud(pud_t pud)
+{
+}
+
#define kvm_virt_to_phys(x) virt_to_idmap((unsigned long)(x))
void kvm_set_way_flush(struct kvm_vcpu *vcpu);
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 106737e..78e68ab 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -58,6 +58,26 @@ static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, kvm, ipa);
}
+/*
+ * D-Cache management functions. They take the page table entries by
+ * value, as they are flushing the cache using the kernel mapping (or
+ * kmap on 32bit).
+ */
+static void kvm_flush_dcache_pte(pte_t pte)
+{
+ __kvm_flush_dcache_pte(pte);
+}
+
+static void kvm_flush_dcache_pmd(pmd_t pmd)
+{
+ __kvm_flush_dcache_pmd(pmd);
+}
+
+static void kvm_flush_dcache_pud(pud_t pud)
+{
+ __kvm_flush_dcache_pud(pud);
+}
+
static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
int min, int max)
{
@@ -119,6 +139,26 @@ static void clear_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr)
put_page(virt_to_page(pmd));
}
+/*
+ * Unmapping vs dcache management:
+ *
+ * If a guest maps certain memory pages as uncached, all writes will
+ * bypass the data cache and go directly to RAM. However, the CPUs
+ * can still speculate reads (not writes) and fill cache lines with
+ * data.
+ *
+ * Those cache lines will be *clean* cache lines though, so a
+ * clean+invalidate operation is equivalent to an invalidate
+ * operation, because no cache lines are marked dirty.
+ *
+ * Those clean cache lines could be filled prior to an uncached write
+ * by the guest, and the cache coherent IO subsystem would therefore
+ * end up writing old data to disk.
+ *
+ * This is why right after unmapping a page/section and invalidating
+ * the corresponding TLBs, we call kvm_flush_dcache_p*() to make sure
+ * the IO subsystem will never hit in the cache.
+ */
static void unmap_ptes(struct kvm *kvm, pmd_t *pmd,
phys_addr_t addr, phys_addr_t end)
{
@@ -128,9 +168,16 @@ static void unmap_ptes(struct kvm *kvm, pmd_t *pmd,
start_pte = pte = pte_offset_kernel(pmd, addr);
do {
if (!pte_none(*pte)) {
+ pte_t old_pte = *pte;
+
kvm_set_pte(pte, __pte(0));
- put_page(virt_to_page(pte));
kvm_tlb_flush_vmid_ipa(kvm, addr);
+
+ /* No need to invalidate the cache for device mappings */
+ if ((pte_val(old_pte) & PAGE_S2_DEVICE) != PAGE_S2_DEVICE)
+ kvm_flush_dcache_pte(old_pte);
+
+ put_page(virt_to_page(pte));
}
} while (pte++, addr += PAGE_SIZE, addr != end);
@@ -149,8 +196,13 @@ static void unmap_pmds(struct kvm *kvm, pud_t *pud,
next = kvm_pmd_addr_end(addr, end);
if (!pmd_none(*pmd)) {
if (kvm_pmd_huge(*pmd)) {
+ pmd_t old_pmd = *pmd;
+
pmd_clear(pmd);
kvm_tlb_flush_vmid_ipa(kvm, addr);
+
+ kvm_flush_dcache_pmd(old_pmd);
+
put_page(virt_to_page(pmd));
} else {
unmap_ptes(kvm, pmd, addr, next);
@@ -173,8 +225,13 @@ static void unmap_puds(struct kvm *kvm, pgd_t *pgd,
next = kvm_pud_addr_end(addr, end);
if (!pud_none(*pud)) {
if (pud_huge(*pud)) {
+ pud_t old_pud = *pud;
+
pud_clear(pud);
kvm_tlb_flush_vmid_ipa(kvm, addr);
+
+ kvm_flush_dcache_pud(old_pud);
+
put_page(virt_to_page(pud));
} else {
unmap_pmds(kvm, pud, addr, next);
@@ -209,10 +266,9 @@ static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd,
pte = pte_offset_kernel(pmd, addr);
do {
- if (!pte_none(*pte)) {
- hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
- kvm_flush_dcache_to_poc((void*)hva, PAGE_SIZE);
- }
+ if (!pte_none(*pte) &&
+ (pte_val(*pte) & PAGE_S2_DEVICE) != PAGE_S2_DEVICE)
+ kvm_flush_dcache_pte(*pte);
} while (pte++, addr += PAGE_SIZE, addr != end);
}
@@ -226,12 +282,10 @@ static void stage2_flush_pmds(struct kvm *kvm, pud_t *pud,
do {
next = kvm_pmd_addr_end(addr, end);
if (!pmd_none(*pmd)) {
- if (kvm_pmd_huge(*pmd)) {
- hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
- kvm_flush_dcache_to_poc((void*)hva, PMD_SIZE);
- } else {
+ if (kvm_pmd_huge(*pmd))
+ kvm_flush_dcache_pmd(*pmd);
+ else
stage2_flush_ptes(kvm, pmd, addr, next);
- }
}
} while (pmd++, addr = next, addr != end);
}
@@ -246,12 +300,10 @@ static void stage2_flush_puds(struct kvm *kvm, pgd_t *pgd,
do {
next = kvm_pud_addr_end(addr, end);
if (!pud_none(*pud)) {
- if (pud_huge(*pud)) {
- hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
- kvm_flush_dcache_to_poc((void*)hva, PUD_SIZE);
- } else {
+ if (pud_huge(*pud))
+ kvm_flush_dcache_pud(*pud);
+ else
stage2_flush_pmds(kvm, pud, addr, next);
- }
}
} while (pud++, addr = next, addr != end);
}
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 92d22e9..cbdc236 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -258,6 +258,24 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
}
}
+static inline void __kvm_flush_dcache_pte(pte_t pte)
+{
+ struct page *page = pte_page(pte);
+ kvm_flush_dcache_to_poc(page_address(page), PAGE_SIZE);
+}
+
+static inline void __kvm_flush_dcache_pmd(pmd_t pmd)
+{
+ struct page *page = pmd_page(pmd);
+ kvm_flush_dcache_to_poc(page_address(page), PMD_SIZE);
+}
+
+static inline void __kvm_flush_dcache_pud(pud_t pud)
+{
+ struct page *page = pud_page(pud);
+ kvm_flush_dcache_to_poc(page_address(page), PUD_SIZE);
+}
+
#define kvm_virt_to_phys(x) __virt_to_phys((unsigned long)(x))
void kvm_set_way_flush(struct kvm_vcpu *vcpu);
--
2.1.2.330.g565301e.dirty
^ permalink raw reply related [flat|nested] 5+ messages in thread* [GIT PULL 3/3] arm/arm64: KVM: Use kernel mapping to perform invalidation on page fault
2015-01-29 22:37 [GIT PULL 0/3] Second round of KVM/ARM fixes for 3.19 Christoffer Dall
2015-01-29 22:37 ` [GIT PULL 1/3] arm/arm64: KVM: Use set/way op trapping to track the state of the caches Christoffer Dall
2015-01-29 22:37 ` [GIT PULL 2/3] arm/arm64: KVM: Invalidate data cache on unmap Christoffer Dall
@ 2015-01-29 22:37 ` Christoffer Dall
2015-01-30 11:30 ` [GIT PULL 0/3] Second round of KVM/ARM fixes for 3.19 Paolo Bonzini
3 siblings, 0 replies; 5+ messages in thread
From: Christoffer Dall @ 2015-01-29 22:37 UTC (permalink / raw)
To: linux-arm-kernel
From: Marc Zyngier <marc.zyngier@arm.com>
When handling a fault in stage-2, we need to resync I$ and D$, just
to be sure we don't leave any old cache line behind.
That's very good, except that we do so using the *user* address.
Under heavy load (swapping like crazy), we may end up in a situation
where the page gets mapped in stage-2 while being unmapped from
userspace by another CPU.
At that point, the DC/IC instructions can generate a fault, which
we handle with kvm->mmu_lock held. The box quickly deadlocks, user
is unhappy.
Instead, perform this invalidation through the kernel mapping,
which is guaranteed to be present. The box is much happier, and so
am I.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
arch/arm/include/asm/kvm_mmu.h | 43 +++++++++++++++++++++++++++++++---------
arch/arm/kvm/mmu.c | 12 +++++++----
arch/arm64/include/asm/kvm_mmu.h | 13 +++++++-----
3 files changed, 50 insertions(+), 18 deletions(-)
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 552c31f..1bca8f8 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -162,13 +162,10 @@ static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
return (vcpu->arch.cp15[c1_SCTLR] & 0b101) == 0b101;
}
-static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
- unsigned long size,
- bool ipa_uncached)
+static inline void __coherent_cache_guest_page(struct kvm_vcpu *vcpu, pfn_t pfn,
+ unsigned long size,
+ bool ipa_uncached)
{
- if (!vcpu_has_cache_enabled(vcpu) || ipa_uncached)
- kvm_flush_dcache_to_poc((void *)hva, size);
-
/*
* If we are going to insert an instruction page and the icache is
* either VIPT or PIPT, there is a potential problem where the host
@@ -180,10 +177,38 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
*
* VIVT caches are tagged using both the ASID and the VMID and doesn't
* need any kind of flushing (DDI 0406C.b - Page B3-1392).
+ *
+ * We need to do this through a kernel mapping (using the
+ * user-space mapping has proved to be the wrong
+ * solution). For that, we need to kmap one page at a time,
+ * and iterate over the range.
*/
- if (icache_is_pipt()) {
- __cpuc_coherent_user_range(hva, hva + size);
- } else if (!icache_is_vivt_asid_tagged()) {
+
+ bool need_flush = !vcpu_has_cache_enabled(vcpu) || ipa_uncached;
+
+ VM_BUG_ON(size & PAGE_MASK);
+
+ if (!need_flush && !icache_is_pipt())
+ goto vipt_cache;
+
+ while (size) {
+ void *va = kmap_atomic_pfn(pfn);
+
+ if (need_flush)
+ kvm_flush_dcache_to_poc(va, PAGE_SIZE);
+
+ if (icache_is_pipt())
+ __cpuc_coherent_user_range((unsigned long)va,
+ (unsigned long)va + PAGE_SIZE);
+
+ size -= PAGE_SIZE;
+ pfn++;
+
+ kunmap_atomic(va);
+ }
+
+vipt_cache:
+ if (!icache_is_pipt() && !icache_is_vivt_asid_tagged()) {
/* any kind of VIPT cache */
__flush_icache_all();
}
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 78e68ab..1366625 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -957,6 +957,12 @@ static bool kvm_is_device_pfn(unsigned long pfn)
return !pfn_valid(pfn);
}
+static void coherent_cache_guest_page(struct kvm_vcpu *vcpu, pfn_t pfn,
+ unsigned long size, bool uncached)
+{
+ __coherent_cache_guest_page(vcpu, pfn, size, uncached);
+}
+
static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
struct kvm_memory_slot *memslot, unsigned long hva,
unsigned long fault_status)
@@ -1046,8 +1052,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
kvm_set_s2pmd_writable(&new_pmd);
kvm_set_pfn_dirty(pfn);
}
- coherent_cache_guest_page(vcpu, hva & PMD_MASK, PMD_SIZE,
- fault_ipa_uncached);
+ coherent_cache_guest_page(vcpu, pfn, PMD_SIZE, fault_ipa_uncached);
ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
} else {
pte_t new_pte = pfn_pte(pfn, mem_type);
@@ -1055,8 +1060,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
kvm_set_s2pte_writable(&new_pte);
kvm_set_pfn_dirty(pfn);
}
- coherent_cache_guest_page(vcpu, hva, PAGE_SIZE,
- fault_ipa_uncached);
+ coherent_cache_guest_page(vcpu, pfn, PAGE_SIZE, fault_ipa_uncached);
ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte,
pgprot_val(mem_type) == pgprot_val(PAGE_S2_DEVICE));
}
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index cbdc236..adcf495 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -243,15 +243,18 @@ static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
return (vcpu_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101;
}
-static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
- unsigned long size,
- bool ipa_uncached)
+static inline void __coherent_cache_guest_page(struct kvm_vcpu *vcpu, pfn_t pfn,
+ unsigned long size,
+ bool ipa_uncached)
{
+ void *va = page_address(pfn_to_page(pfn));
+
if (!vcpu_has_cache_enabled(vcpu) || ipa_uncached)
- kvm_flush_dcache_to_poc((void *)hva, size);
+ kvm_flush_dcache_to_poc(va, size);
if (!icache_is_aliasing()) { /* PIPT */
- flush_icache_range(hva, hva + size);
+ flush_icache_range((unsigned long)va,
+ (unsigned long)va + size);
} else if (!icache_is_aivivt()) { /* non ASID-tagged VIVT */
/* any kind of VIPT cache */
__flush_icache_all();
--
2.1.2.330.g565301e.dirty
^ permalink raw reply related [flat|nested] 5+ messages in thread