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From: Jan Beulich <jbeulich@suse.com>
Subject: x86/HVM: don't load LDTR with VM86 mode attrs during task switch
Just like TR, LDTR is purely a protected mode facility and hence needs
to be loaded accordingly. Also move its loading to where it
architecurally belongs.
This is XSA-192.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Tested-by: Andrew Cooper <andrew.cooper3@citrix.com>
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2728,17 +2728,16 @@ static void hvm_unmap_entry(void *p)
}
static int hvm_load_segment_selector(
- enum x86_segment seg, uint16_t sel)
+ enum x86_segment seg, uint16_t sel, unsigned int eflags)
{
struct segment_register desctab, cs, segr;
struct desc_struct *pdesc, desc;
u8 dpl, rpl, cpl;
bool_t writable;
int fault_type = TRAP_invalid_tss;
- struct cpu_user_regs *regs = guest_cpu_user_regs();
struct vcpu *v = current;
- if ( regs->eflags & X86_EFLAGS_VM )
+ if ( eflags & X86_EFLAGS_VM )
{
segr.sel = sel;
segr.base = (uint32_t)sel << 4;
@@ -2986,6 +2985,8 @@ void hvm_task_switch(
if ( rc != HVMCOPY_okay )
goto out;
+ if ( hvm_load_segment_selector(x86_seg_ldtr, tss.ldt, 0) )
+ goto out;
if ( hvm_set_cr3(tss.cr3, 1) )
goto out;
@@ -3008,13 +3009,12 @@ void hvm_task_switch(
}
exn_raised = 0;
- if ( hvm_load_segment_selector(x86_seg_ldtr, tss.ldt) ||
- hvm_load_segment_selector(x86_seg_es, tss.es) ||
- hvm_load_segment_selector(x86_seg_cs, tss.cs) ||
- hvm_load_segment_selector(x86_seg_ss, tss.ss) ||
- hvm_load_segment_selector(x86_seg_ds, tss.ds) ||
- hvm_load_segment_selector(x86_seg_fs, tss.fs) ||
- hvm_load_segment_selector(x86_seg_gs, tss.gs) )
+ if ( hvm_load_segment_selector(x86_seg_es, tss.es, tss.eflags) ||
+ hvm_load_segment_selector(x86_seg_cs, tss.cs, tss.eflags) ||
+ hvm_load_segment_selector(x86_seg_ss, tss.ss, tss.eflags) ||
+ hvm_load_segment_selector(x86_seg_ds, tss.ds, tss.eflags) ||
+ hvm_load_segment_selector(x86_seg_fs, tss.fs, tss.eflags) ||
+ hvm_load_segment_selector(x86_seg_gs, tss.gs, tss.eflags) )
exn_raised = 1;
rc = hvm_copy_to_guest_virt(
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