Author: jhb
Date: Mon Oct 15 18:12:25 2018
New Revision: 339364
URL: https://svnweb.freebsd.org/changeset/base/339364
Log:
Reload the LDT selector after an AMD-v #VMEXIT.
cpu_switch() always reloads the LDT, so this can only affect the
hypervisor process itself. Fix this by explicitly reloading the host
LDT selector after each #VMEXIT. The stock bhyve process on FreeBSD
never uses a custom LDT, so this change is cosmetic.
Reviewed by: kib
Tested by: Mike Tancsa <m...@sentex.net>
Approved by: re (gjb)
MFC after: 2 weeks
Modified:
head/sys/amd64/vmm/amd/svm.c
Modified: head/sys/amd64/vmm/amd/svm.c
==============================================================================
--- head/sys/amd64/vmm/amd/svm.c Mon Oct 15 17:50:02 2018
(r339363)
+++ head/sys/amd64/vmm/amd/svm.c Mon Oct 15 18:12:25 2018
(r339364)
@@ -1940,6 +1940,7 @@ svm_vmrun(void *arg, int vcpu, register_t rip, pmap_t
struct vm *vm;
uint64_t vmcb_pa;
int handled;
+ uint16_t ldt_sel;
svm_sc = arg;
vm = svm_sc->vm;
@@ -2024,6 +2025,15 @@ svm_vmrun(void *arg, int vcpu, register_t rip, pmap_t
break;
}
+ /*
+ * #VMEXIT resumes the host with the guest LDTR, so
+ * save the current LDT selector so it can be restored
+ * after an exit. The userspace hypervisor probably
+ * doesn't use a LDT, but save and restore it to be
+ * safe.
+ */
+ ldt_sel = sldt();
+
svm_inj_interrupts(svm_sc, vcpu, vlapic);
/* Activate the nested pmap on 'curcpu' */
@@ -2053,6 +2063,9 @@ svm_vmrun(void *arg, int vcpu, register_t rip, pmap_t
* to be restored explicitly.
*/
restore_host_tss();
+
+ /* Restore host LDTR. */
+ lldt(ldt_sel);
/* #VMEXIT disables interrupts so re-enable them here. */
enable_gintr();
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