[PATCHv2] Add async page fault test

[Gleb Natapov <gleb@redhat.com>]

The test checks that when hypervisor prefaults swapped in page it does
not generates spurious #PFs in case page was unmapped while it was
swapped out.

diff --git a/config-x86-common.mak b/config-x86-common.mak
index c8fbda7..6976f78 100644
--- a/config-x86-common.mak
+++ b/config-x86-common.mak
@@ -34,7 +34,7 @@ tests-common = $(TEST_DIR)/vmexit.flat $(TEST_DIR)/tsc.flat \
                $(TEST_DIR)/realmode.flat $(TEST_DIR)/msr.flat \
                $(TEST_DIR)/hypercall.flat $(TEST_DIR)/sieve.flat \
                $(TEST_DIR)/kvmclock_test.flat  $(TEST_DIR)/eventinj.flat \
-               $(TEST_DIR)/s3.flat $(TEST_DIR)/pmu.flat
+               $(TEST_DIR)/s3.flat $(TEST_DIR)/pmu.flat $(TEST_DIR)/asyncpf.flat
 
 ifdef API
 tests-common += api/api-sample
@@ -90,6 +90,8 @@ $(TEST_DIR)/s3.elf: $(cstart.o) $(TEST_DIR)/s3.o
 
 $(TEST_DIR)/pmu.elf: $(cstart.o) $(TEST_DIR)/pmu.o
 
+$(TEST_DIR)/asyncpf.elf: $(cstart.o) $(TEST_DIR)/asyncpf.o
+
 arch_clean:
 	$(RM) $(TEST_DIR)/*.o $(TEST_DIR)/*.flat $(TEST_DIR)/*.elf \
 	$(TEST_DIR)/.*.d $(TEST_DIR)/lib/.*.d $(TEST_DIR)/lib/*.o
diff --git a/lib/x86/processor.h b/lib/x86/processor.h
index c7e1afb..e46d8d0 100644
--- a/lib/x86/processor.h
+++ b/lib/x86/processor.h
@@ -302,4 +302,9 @@ static inline void invlpg(void *va)
 {
 	asm volatile("invlpg (%0)" ::"r" (va) : "memory");
 }
+
+static inline void safe_halt(void)
+{
+	asm volatile("sti; hlt");
+}
 #endif
diff --git a/lib/x86/vm.c b/lib/x86/vm.c
index 550ec9b..71b70fd 100644
--- a/lib/x86/vm.c
+++ b/lib/x86/vm.c
@@ -219,6 +219,11 @@ void *vmalloc(unsigned long size)
     return mem;
 }
 
+uint64_t virt_to_phys_cr3(void *mem)
+{
+    return (get_pte(phys_to_virt(read_cr3()), mem) & PTE_ADDR) + ((ulong)mem & (PAGE_SIZE - 1));
+}
+
 void vfree(void *mem)
 {
     unsigned long size = ((unsigned long *)mem)[-1];
diff --git a/lib/x86/vm.h b/lib/x86/vm.h
index 71ab4a8..3473f8d 100644
--- a/lib/x86/vm.h
+++ b/lib/x86/vm.h
@@ -22,6 +22,7 @@ void vfree(void *mem);
 void *vmap(unsigned long long phys, unsigned long size);
 void *alloc_vpage(void);
 void *alloc_vpages(ulong nr);
+uint64_t virt_to_phys_cr3(void *mem);
 
 void install_pte(unsigned long *cr3,
                         int pte_level,
diff --git a/x86/asyncpf.c b/x86/asyncpf.c
new file mode 100644
index 0000000..62c0455
--- /dev/null
+++ b/x86/asyncpf.c
@@ -0,0 +1,113 @@
+/*
+ * Async PF test. For the test to actually do anywathing it ineeds to be started
+ * in memory cgroup with 512M of memory and with more then 1G memory provided 
+ * to the guest.
+ *
+ * To create cgroup do as root:
+ * mkdir /dev/cgroup
+ * mount -t cgroup none -omemory /dev/cgroup
+ * chmod a+rxw /dev/cgroup/
+ *
+ * From a shell you will start qemu from:
+ * mkdir /dev/cgroup/1
+ * echo $$ >  /dev/cgroup/1/tasks
+ * echo 512M > /dev/cgroup/1/memory.limit_in_bytes
+ *
+ */
+#include "x86/msr.h"
+#include "x86/processor.h"
+#include "x86/apic-defs.h"
+#include "x86/apic.h"
+#include "x86/desc.h"
+#include "x86/isr.h"
+#include "x86/vm.h"
+
+#include "libcflat.h"
+#include <stdint.h>
+
+#define KVM_PV_REASON_PAGE_NOT_PRESENT 1
+#define KVM_PV_REASON_PAGE_READY 2
+
+#define MSR_KVM_ASYNC_PF_EN 0x4b564d02
+
+#define KVM_ASYNC_PF_ENABLED                    (1 << 0)
+#define KVM_ASYNC_PF_SEND_ALWAYS                (1 << 1)
+
+volatile uint32_t apf_reason __attribute__((aligned(64)));
+char *buf;
+volatile uint64_t  i;
+volatile uint64_t phys;
+bool fail;
+
+static inline uint32_t get_apf_reason(void)
+{
+	uint32_t r = apf_reason;
+	apf_reason = 0;
+	return r;
+}
+
+static void pf_isr(struct ex_regs *r)
+{
+	void* virt = (void*)((ulong)(buf+i) & ~(PAGE_SIZE-1));
+	uint32_t reason = get_apf_reason();
+
+	switch (reason) {
+		case 0:
+			printf("unexpected #PF at %p\n", read_cr2());
+			fail = true;
+			break;
+		case KVM_PV_REASON_PAGE_NOT_PRESENT:
+			phys = virt_to_phys_cr3(virt);
+			install_pte(phys_to_virt(read_cr3()), 1, virt, phys, 0);
+			write_cr3(read_cr3());
+			printf("Got not present #PF token %x virt addr %p phys addr %p\n", read_cr2(), virt, phys);
+			while(phys) {
+				safe_halt(); /* enables irq */
+				irq_disable();
+			}
+			break;
+		case KVM_PV_REASON_PAGE_READY:
+			printf("Got present #PF token %x\n", read_cr2());
+			if ((uint32_t)read_cr2() == ~0)
+				break;
+			install_pte(phys_to_virt(read_cr3()), 1, virt, phys | PTE_PRESENT | PTE_WRITE, 0);
+			write_cr3(read_cr3());
+			phys = 0;
+			break;
+		default:
+			printf("unexpected async pf reason %d\n", reason);
+			fail = true;
+			break;
+	}
+}
+
+#define MEM 1ull*1024*1024*1024
+
+int main(int ac, char **av)
+{
+	int loop = 2;
+
+	setup_vm();
+	setup_idt();
+	setup_gdt();
+	printf("install handler\n");
+	handle_exception(14, pf_isr);
+	apf_reason = 0;
+	printf("enable async pf\n");
+	wrmsr(MSR_KVM_ASYNC_PF_EN, virt_to_phys((void*)&apf_reason) |
+			KVM_ASYNC_PF_SEND_ALWAYS | KVM_ASYNC_PF_ENABLED);
+	printf("alloc memory\n");
+	buf = vmalloc(MEM);
+	irq_enable();
+	while(loop--) {
+		printf("start loop\n");
+		/* access a lot of memory to make host swap it out */
+		for (i=0; i < MEM; i+=4096)
+			buf[i] = 1;
+		printf("end loop\n");
+	}
+	irq_disable();
+
+	printf("%s\n", fail ? "FAIL" : "PASS");
+	return fail;
+}
--
			Gleb.