[PATCH 54/58] KVM: Flush remote tlbs when reducing shadow pte permissions

Avi Kivity
2007-06-17T09:44:35Z

When a vcpu causes a shadow tlb entry to have reduced permissions, it
must also clear the tlb on remote vcpus. We do that by:

- setting a bit on the vcpu that requests a tlb flush before the next entry
- if the vcpu is currently executing, we send an ipi to make sure it
exits before we continue

Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
drivers/kvm/kvm.h | 8 ++++++++
drivers/kvm/kvm_main.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
drivers/kvm/mmu.c | 8 +++++---
drivers/kvm/svm.c | 17 ++++++++++++-----
drivers/kvm/vmx.c | 22 +++++++++++++++-------
5 files changed, 84 insertions(+), 15 deletions(-)

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 528a56b..b08272b 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -84,6 +84,11 @@
#define KVM_PIO_PAGE_OFFSET 1

/*
+ * vcpu->requests bit members
+ */
+#define KVM_TLB_FLUSH 0
+
+/*
* Address types:
*
* gva - guest virtual address
@@ -272,6 +277,8 @@ struct kvm_vcpu {
u64 host_tsc;
struct kvm_run *run;
int interrupt_window_open;
+ int guest_mode;
+ unsigned long requests;
unsigned long irq_summary; /* bit vector: 1 per word in irq_pending */
#define NR_IRQ_WORDS KVM_IRQ_BITMAP_SIZE(unsigned long)
unsigned long irq_pending[NR_IRQ_WORDS];
@@ -530,6 +537,7 @@ void save_msrs(struct vmx_msr_entry *e, int n);
void kvm_resched(struct kvm_vcpu *vcpu);
void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
+void kvm_flush_remote_tlbs(struct kvm *kvm);

int kvm_read_guest(struct kvm_vcpu *vcpu,
gva_t addr,
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 4e1a017..633c2ed 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -41,6 +41,8 @@
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/sched.h>
+#include <linux/cpumask.h>
+#include <linux/smp.h>

#include "x86_emulate.h"
#include "segment_descriptor.h"
@@ -309,6 +311,48 @@ static void vcpu_put(struct kvm_vcpu *vcpu)
mutex_unlock(&vcpu->mutex);
}

+static void ack_flush(void *_completed)
+{
+ atomic_t *completed = _completed;
+
+ atomic_inc(completed);
+}
+
+void kvm_flush_remote_tlbs(struct kvm *kvm)
+{
+ int i, cpu, needed;
+ cpumask_t cpus;
+ struct kvm_vcpu *vcpu;
+ atomic_t completed;
+
+ atomic_set(&completed, 0);
+ cpus_clear(cpus);
+ needed = 0;
+ for (i = 0; i < kvm->nvcpus; ++i) {
+ vcpu = &kvm->vcpus[i];
+ if (test_and_set_bit(KVM_TLB_FLUSH, &vcpu->requests))
+ continue;
+ cpu = vcpu->cpu;
+ if (cpu != -1 && cpu != raw_smp_processor_id())
+ if (!cpu_isset(cpu, cpus)) {
+ cpu_set(cpu, cpus);
+ ++needed;
+ }
+ }
+
+ /*
+ * We really want smp_call_function_mask() here. But that's not
+ * available, so ipi all cpus in parallel and wait for them
+ * to complete.
+ */
+ for (cpu = first_cpu(cpus); cpu != NR_CPUS; cpu = next_cpu(cpu, cpus))
+ smp_call_function_single(cpu, ack_flush, &completed, 1, 0);
+ while (atomic_read(&completed) != needed) {
+ cpu_relax();
+ barrier();
+ }
+}
+
static struct kvm *kvm_create_vm(void)
{
struct kvm *kvm = kzalloc(sizeof(struct kvm), GFP_KERNEL);
diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index d4de988..ad50cfd 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -441,7 +441,7 @@ static void rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn)
BUG_ON(!(*spte & PT_WRITABLE_MASK));
rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
rmap_remove(vcpu, spte);
- kvm_arch_ops->tlb_flush(vcpu);
+ kvm_flush_remote_tlbs(vcpu->kvm);
set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);
}
}
@@ -656,7 +656,7 @@ static void kvm_mmu_page_unlink_children(struct kvm_vcpu *vcpu,
rmap_remove(vcpu, &pt[i]);
pt[i] = 0;
}
- kvm_arch_ops->tlb_flush(vcpu);
+ kvm_flush_remote_tlbs(vcpu->kvm);
return;
}

@@ -669,6 +669,7 @@ static void kvm_mmu_page_unlink_children(struct kvm_vcpu *vcpu,
ent &= PT64_BASE_ADDR_MASK;
mmu_page_remove_parent_pte(vcpu, page_header(ent), &pt[i]);
}
+ kvm_flush_remote_tlbs(vcpu->kvm);
}

static void kvm_mmu_put_page(struct kvm_vcpu *vcpu,
@@ -1093,6 +1094,7 @@ static void mmu_pte_write_zap_pte(struct kvm_vcpu *vcpu,
}
}
*spte = 0;
+ kvm_flush_remote_tlbs(vcpu->kvm);
}

static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
@@ -1308,7 +1310,7 @@ void kvm_mmu_zap_all(struct kvm_vcpu *vcpu)
}

mmu_free_memory_caches(vcpu);
- kvm_arch_ops->tlb_flush(vcpu);
+ kvm_flush_remote_tlbs(vcpu->kvm);
init_kvm_mmu(vcpu);
}

diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index 70f386e..eb175c5 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -1470,6 +1470,11 @@ static void load_db_regs(unsigned long *db_regs)
asm volatile ("mov %0, %%dr3" : : "r"(db_regs[3]));
}

+static void svm_flush_tlb(struct kvm_vcpu *vcpu)
+{
+ force_new_asid(vcpu);
+}
+
static int svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
u16 fs_selector;
@@ -1487,6 +1492,11 @@ again:

clgi();

+ vcpu->guest_mode = 1;
+ if (vcpu->requests)
+ if (test_and_clear_bit(KVM_TLB_FLUSH, &vcpu->requests))
+ svm_flush_tlb(vcpu);
+
pre_svm_run(vcpu);

save_host_msrs(vcpu);
@@ -1618,6 +1628,8 @@ again:
#endif
: "cc", "memory" );

+ vcpu->guest_mode = 0;
+
if (vcpu->fpu_active) {
fx_save(vcpu->guest_fx_image);
fx_restore(vcpu->host_fx_image);
@@ -1682,11 +1694,6 @@ again:
return r;
}

-static void svm_flush_tlb(struct kvm_vcpu *vcpu)
-{
- force_new_asid(vcpu);
-}
-
static void svm_set_cr3(struct kvm_vcpu *vcpu, unsigned long root)
{
vcpu->svm->vmcb->save.cr3 = root;
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index a1f51b9..b969db1 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -1972,6 +1972,11 @@ static int dm_request_for_irq_injection(struct kvm_vcpu *vcpu,
(vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF));
}

+static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
+{
+ vmcs_writel(GUEST_CR3, vmcs_readl(GUEST_CR3));
+}
+
static int vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
u8 fail;
@@ -1997,9 +2002,15 @@ again:
*/
vmcs_writel(HOST_CR0, read_cr0());

+ local_irq_disable();
+
+ vcpu->guest_mode = 1;
+ if (vcpu->requests)
+ if (test_and_clear_bit(KVM_TLB_FLUSH, &vcpu->requests))
+ vmx_flush_tlb(vcpu);
+
asm (
/* Store host registers */
- "pushf \n\t"
#ifdef CONFIG_X86_64
"push %%rax; push %%rbx; push %%rdx;"
"push %%rsi; push %%rdi; push %%rbp;"
@@ -2091,7 +2102,6 @@ again:
"pop %%ecx; popa \n\t"
#endif
"setbe %0 \n\t"
- "popf \n\t"
: "=q" (fail)
: "r"(vcpu->launched), "d"((unsigned long)HOST_RSP),
"c"(vcpu),
@@ -2115,6 +2125,9 @@ again:
[cr2]"i"(offsetof(struct kvm_vcpu, cr2))
: "cc", "memory" );

+ vcpu->guest_mode = 0;
+ local_irq_enable();
+
++vcpu->stat.exits;

vcpu->interrupt_window_open = (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0;
@@ -2167,11 +2180,6 @@ out:
return r;
}

-static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
-{
- vmcs_writel(GUEST_CR3, vmcs_readl(GUEST_CR3));
-}
-
static void vmx_inject_page_fault(struct kvm_vcpu *vcpu,
unsigned long addr,
u32 err_code)