kvm: Hardcode a "reset vector" at f000:fff0

It seems that if we attempt to run code at any other location than f000:fff0,
we get an KVM_EXIT_UNKNOWN error. To work around that, hardcode a "reset
vector" at f000:fff0 that jumps to 0000:0x7c000 and load the kernel at the
latter location.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

diff --git a/tools/kvm/kvm.c b/tools/kvm/kvm.c
index b5a20b68b42f3bb2caa5e2a5ba691f8dce7c5ab0..5b241137cc232dd9db19918a7b8fbd66daeecc09 100644 (file)
--- a/tools/kvm/kvm.c
+++ b/tools/kvm/kvm.c
@@ -153,8 +153,13 @@ static inline uint32_t segment_to_flat(uint16_t selector, uint16_t offset)
        return ((uint32_t)selector << 4) + (uint32_t) offset;
 }
 
-#define BIN_BOOT_LOADER_CS     0xf000
-#define BIN_BOOT_LOADER_IP     0xfff0
+#define RESET_CS               0xf000
+#define RESET_IP               0xfff0
+
+#define BIN_BOOT_LOADER_CS     0x0000
+#define BIN_BOOT_LOADER_IP     0x7c00
+
+static unsigned char reset_code[] = { 0xea, 0x00, 0x7c, 0x00, 0x00 };
 
 static int load_flat_binary(struct kvm *kvm, int fd)
 {
@@ -169,8 +174,12 @@ static int load_flat_binary(struct kvm *kvm, int fd)
        while ((nr = read(fd, p, 65536)) > 0)
                p += nr;
 
-       kvm->boot_cs    = BIN_BOOT_LOADER_CS;
-       kvm->boot_ip    = BIN_BOOT_LOADER_IP;
+       p = guest_addr_to_host(kvm, segment_to_flat(RESET_CS, RESET_IP));
+
+       memcpy(p, reset_code, ARRAY_SIZE(reset_code));
+
+       kvm->boot_cs    = RESET_CS;
+       kvm->boot_ip    = RESET_IP;
 
        return true;
 }
@@ -230,8 +239,12 @@ static bool load_bzimage(struct kvm *kvm, int fd)
        while ((nr = read(fd, p, 65536)) > 0)
                p += nr;
 
-       kvm->boot_cs    = 0;
-       kvm->boot_ip    = BZ_BOOT_LOADER_START;
+       p = guest_addr_to_host(kvm, segment_to_flat(RESET_CS, RESET_IP));
+
+       memcpy(p, reset_code, ARRAY_SIZE(reset_code));
+
+       kvm->boot_cs    = RESET_CS;
+       kvm->boot_ip    = RESET_IP;
 
        return true;
 }
@@ -457,6 +470,12 @@ void kvm__show_code(struct kvm *self)
        unsigned int i;
        uint8_t *ip;
 
+       if (ioctl(self->vcpu_fd, KVM_GET_REGS, &self->regs) < 0)
+               die("KVM_GET_REGS failed");
+
+       if (ioctl(self->vcpu_fd, KVM_GET_SREGS, &self->sregs) < 0)
+               die("KVM_GET_SREGS failed");
+
        ip = guest_addr_to_host(self, ip_real_to_flat(self, self->regs.rip) - code_prologue);
 
        printf("Code: ");

diff --git a/tools/kvm/util.h b/tools/kvm/util.h
index ddb276871c4f70f245effff136d7cb966787edaa..fa91b95cb0560500100849de02177cbf6af96ff3 100644 (file)
--- a/tools/kvm/util.h
+++ b/tools/kvm/util.h
@@ -1,6 +1,8 @@
 #ifndef UTIL_H_
 #define UTIL_H_
 
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
 /*
  * Some bits are stolen from perf tool :)
  */