Mailing List Archive

[xen staging] x86/svm: Fix handling of EFLAGS.RF on task switch
commit a57e0b39800242a0fc3ef76c9cb642f10a1a5cbd
Author: Andrew Cooper <andrew.cooper3@citrix.com>
AuthorDate: Tue Dec 3 16:59:09 2019 +0000
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Thu Dec 5 13:19:28 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@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
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 290bd4c882..7cb235a667 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 7450cbe40d..bafc3b30c5 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3963,7 +3963,8 @@ 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#staging

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