[PATCH] KVM: MMU: Support emulated writes into RAM

As the mmu write protects guest page table, we emulate those writes.  Since
they are not mmio, there is no need to go to userspace to perform them.

So, perform the writes in the kernel if possible, and notify the mmu about
them so it can take the approriate action.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 58b9deb0bc0e9558fc697a8acb7e265f2d9a1452..b7068ecd7765ad5956efb6a8d779a40c4aa836d6 100644 (file)
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -448,6 +448,9 @@ int kvm_write_guest(struct kvm_vcpu *vcpu,
 
 unsigned long segment_base(u16 selector);
 
+void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes);
+void kvm_mmu_post_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes);
+
 static inline struct page *_gfn_to_page(struct kvm *kvm, gfn_t gfn)
 {
        struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 68e121eeccbc60467a31bf1b3e48db4dd19d1a26..047f6f6ed3f67580be892f0570977725c6e0f86a 100644 (file)
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -877,6 +877,27 @@ static int emulator_read_emulated(unsigned long addr,
        }
 }
 
+static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
+                              unsigned long val, int bytes)
+{
+       struct kvm_memory_slot *m;
+       struct page *page;
+       void *virt;
+
+       if (((gpa + bytes - 1) >> PAGE_SHIFT) != (gpa >> PAGE_SHIFT))
+               return 0;
+       m = gfn_to_memslot(vcpu->kvm, gpa >> PAGE_SHIFT);
+       if (!m)
+               return 0;
+       page = gfn_to_page(m, gpa >> PAGE_SHIFT);
+       kvm_mmu_pre_write(vcpu, gpa, bytes);
+       virt = kmap_atomic(page, KM_USER0);
+       memcpy(virt + offset_in_page(gpa), &val, bytes);
+       kunmap_atomic(virt, KM_USER0);
+       kvm_mmu_post_write(vcpu, gpa, bytes);
+       return 1;
+}
+
 static int emulator_write_emulated(unsigned long addr,
                                   unsigned long val,
                                   unsigned int bytes,
@@ -888,6 +909,9 @@ static int emulator_write_emulated(unsigned long addr,
        if (gpa == UNMAPPED_GVA)
                return X86EMUL_PROPAGATE_FAULT;
 
+       if (emulator_write_phys(vcpu, gpa, val, bytes))
+               return X86EMUL_CONTINUE;
+
        vcpu->mmio_needed = 1;
        vcpu->mmio_phys_addr = gpa;
        vcpu->mmio_size = bytes;

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index ceae25bfd4b507db2837c2ce36d64b3e3995d462..bce7eb21f7399a3dcc8b648359c4625f87aeb978 100644 (file)
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -956,6 +956,15 @@ int kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
        return init_kvm_mmu(vcpu);
 }
 
+void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)
+{
+       pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes);
+}
+
+void kvm_mmu_post_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)
+{
+}
+
 static void free_mmu_pages(struct kvm_vcpu *vcpu)
 {
        while (!list_empty(&vcpu->free_pages)) {