KVM: disable writeback for 0x0f 0x01 instructions.

0x0f 0x01 instructions (ie lgdt, lidt, smsw, lmsw and invlpg) does
not use writeback. This patch set no_wb=1 when emulating those
instructions.

This fixes a regression booting the FreeBSD kernel on AMD.

Signed-off-by: Aurelien Jarno <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 1b800fc00342c55dbdb47c21935345330b49c4ef..1f979cb0df314f82cab71e88f2c7892922454860 100644 (file)
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -1178,6 +1178,8 @@ pop_instruction:
 twobyte_insn:
        switch (b) {
        case 0x01: /* lgdt, lidt, lmsw */
+               /* Disable writeback. */
+               no_wb = 1;
                switch (modrm_reg) {
                        u16 size;
                        unsigned long address;