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kvm: Remove 'reset vector' hack

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As explained by Avi Kivity, KVM on Intel requires segment 'base' to equal to
'selector * 16'.  Fix that up and remove the 'reset vector' hack.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
This commit is contained in:
Pekka Enberg
2015-06-01 16:39:38 +01:00
committed by Will Deacon
parent 54d4a62605
commit 147c74c2e7
1 changed files with 7 additions and 26 deletions
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kvm.c
+7 -26
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@@ -153,27 +153,6 @@ static inline uint32_t segment_to_flat(uint16_t selector, uint16_t offset)
return ((uint32_t)selector << 4) + (uint32_t) offset;
}
/*
* HACK ALERT! KVM seems to be unable to run 16-bit real mode if 'cs' selector
* does not equal to 0xf000 at the beginning. To work around that, we need a
* 'reset vector' at 0xf000:0xfff0 that has an hard-coded jump to 0x000:0x7c000
* where we also load the Linux kernel boot sector and setup code.
*/
#define RESET_VECTOR_CS 0xf000
#define RESET_VECTOR_IP 0xfff0
static unsigned char reset_vector_code[] = { 0xea, 0x00, 0x7c, 0x00, 0x00 };
static void load_reset_vector(struct kvm *self)
{
void *p;
p = guest_addr_to_host(self, segment_to_flat(RESET_VECTOR_CS, RESET_VECTOR_IP));
memcpy(p, reset_vector_code, ARRAY_SIZE(reset_vector_code));
}
#define BOOT_LOADER_CS 0x0000
#define BOOT_LOADER_IP 0x7c00
@@ -284,13 +263,15 @@ static inline uint64_t ip_real_to_flat(struct kvm *self, uint64_t ip)
void kvm__reset_vcpu(struct kvm *self)
{
load_reset_vector(self);
self->sregs = (struct kvm_sregs) {
.cr0 = 0x60000010ULL,
.cs = (struct kvm_segment) {
.selector = RESET_VECTOR_CS,
.base = 0xffff0000UL,
/*
* KVM on Intel requires 'base' to be 'selector * 16' in
* real mode.
*/
.selector = BOOT_LOADER_CS,
.base = BOOT_LOADER_CS * 16,
.limit = 0xffffU,
.type = 0x0bU,
.present = 1,
@@ -354,7 +335,7 @@ void kvm__reset_vcpu(struct kvm *self)
die_perror("KVM_SET_SREGS failed");
self->regs = (struct kvm_regs) {
.rip = RESET_VECTOR_IP,
.rip = BOOT_LOADER_IP,
/* We start the guest in 16-bit real mode */
.rflags = 0x0000000000000002ULL,
};