[Xen-changelog] [xen stable-4.13] x86/svm: Fix handling of EFLAGS.RF on task switch

[patchbot@xxxxxxx]

commit ecd3e34ff88b4a8130e7bc6dc18b09682ac3da2b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Dec 3 16:59:09 2019 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Dec 11 17:10:39 2019 +0000

    x86/svm: Fix handling of EFLAGS.RF on task switch
    
    VT-x updates RF before vmexit, so eflags written into the outgoing TSS 
happens
    to be correct.  SVM does not update RF before vmexit, and instead provides 
it
    via a bit in exitinfo2.
    
    In practice, needing RF set in the outgoing state occurs when a task gate is
    used to handle faults.
    
    Extend hvm_task_switch() with an extra_eflags parameter which gets fed into
    the outgoing TSS, and fill it in suitably from the SVM vmexit information.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c        | 4 ++--
 xen/arch/x86/hvm/svm/svm.c    | 3 ++-
 xen/arch/x86/hvm/vmx/vmx.c    | 3 ++-
 xen/include/asm-x86/hvm/hvm.h | 2 +-
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 7f556171bd..47573f71b8 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2913,7 +2913,7 @@ void hvm_prepare_vm86_tss(struct vcpu *v, uint32_t base, 
uint32_t limit)
 
 void hvm_task_switch(
     uint16_t tss_sel, enum hvm_task_switch_reason taskswitch_reason,
-    int32_t errcode, unsigned int insn_len)
+    int32_t errcode, unsigned int insn_len, unsigned int extra_eflags)
 {
     struct vcpu *v = current;
     struct cpu_user_regs *regs = guest_cpu_user_regs();
@@ -2988,7 +2988,7 @@ void hvm_task_switch(
         eflags &= ~X86_EFLAGS_NT;
 
     tss.eip    = regs->eip + insn_len;
-    tss.eflags = eflags;
+    tss.eflags = eflags | extra_eflags;
     tss.eax    = regs->eax;
     tss.ecx    = regs->ecx;
     tss.edx    = regs->edx;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 0fb1908c18..6ae43999ff 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2812,7 +2812,8 @@ void svm_vmexit_handler(struct cpu_user_regs *regs)
         if ( (vmcb->exitinfo2 >> 44) & 1 )
             errcode = (uint32_t)vmcb->exitinfo2;
 
-        hvm_task_switch(vmcb->exitinfo1, reason, errcode, insn_len);
+        hvm_task_switch(vmcb->exitinfo1, reason, errcode, insn_len,
+                        (vmcb->exitinfo2 & (1ul << 48)) ? X86_EFLAGS_RF : 0);
         break;
     }
 
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 6e57e888f9..e70096b798 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3999,7 +3999,8 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
         else
              ecode = -1;
 
-        hvm_task_switch(exit_qualification, reasons[source], ecode, inst_len);
+        hvm_task_switch(exit_qualification, reasons[source], ecode, inst_len,
+                        0 /* EFLAGS.RF already updated. */);
         break;
     }
     case EXIT_REASON_CPUID:
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 17fb7efa6e..1d7b66f927 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -296,7 +296,7 @@ void hvm_set_rdtsc_exiting(struct domain *d, bool_t enable);
 enum hvm_task_switch_reason { TSW_jmp, TSW_iret, TSW_call_or_int };
 void hvm_task_switch(
     uint16_t tss_sel, enum hvm_task_switch_reason taskswitch_reason,
-    int32_t errcode, unsigned int insn_len);
+    int32_t errcode, unsigned int insn_len, unsigned int extra_eflags);
 
 enum hvm_access_type {
     hvm_access_insn_fetch,
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13

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