Under FRED, entry_from_pv() handles everything. To start with, implement
exception handling in the same manner as entry_from_xen(), although we can
unconditionally enable interrupts after the async/fatal events.
After entry_from_pv() returns, test_all_events() needs to run to perform
exception and interrupt injection. Split entry_FRED_R3() into two and
introduce eretu_exit_to_guest() as the latter half, coming unilaterally from
restore_all_guest().
For all of this, there is a slightly complicated relationship with CONFIG_PV.
entry_FRED_R3() must exist irrespective of CONFIG_PV, because it's the
entrypoint registered with hardware. For simplicity, entry_from_pv() is
always called, but it collapses into fatal_trap() in the !PV case.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
v3:
* Adjust comments.
* Group CP with others. It's definitely wrong for perf, but that's out the
window anyway now that we're letting a compiler make the decision tree.
v2:
* New
---
xen/arch/x86/traps.c | 75 +++++++++++++++++++++++++++++++-
xen/arch/x86/x86_64/entry-fred.S | 13 +++++-
xen/arch/x86/x86_64/entry.S | 4 +-
3 files changed, 89 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 0027f096a6c3..3f7db11c247b 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2266,9 +2266,82 @@ void asmlinkage check_ist_exit(const struct cpu_user_regs *regs, bool ist_exit)
void asmlinkage entry_from_pv(struct cpu_user_regs *regs)
{
+ struct fred_info *fi = cpu_regs_fred_info(regs);
+ uint8_t type = regs->fred_ss.type;
+ uint8_t vec = regs->fred_ss.vector;
+
/* Copy fred_ss.vector into entry_vector as IDT delivery would have done. */
- regs->entry_vector = regs->fred_ss.vector;
+ regs->entry_vector = vec;
+
+ if ( !IS_ENABLED(CONFIG_PV) )
+ goto fatal;
+
+ /*
+ * First, handle the asynchronous or fatal events. These are either
+ * unrelated to the interrupted context, or may not have valid context
+ * recorded, and all have special rules on how/whether to re-enable IRQs.
+ */
+ switch ( type )
+ {
+ case X86_ET_EXT_INTR:
+ return do_IRQ(regs);
+
+ case X86_ET_NMI:
+ return do_nmi(regs);
+
+ case X86_ET_HW_EXC:
+ switch ( vec )
+ {
+ case X86_EXC_DF: return do_double_fault(regs);
+ case X86_EXC_MC: return do_machine_check(regs);
+ }
+ break;
+ }
+
+ /*
+ * With the asynchronous events handled, what remains are the synchronous
+ * ones. PV guest context always had interrupts enabled.
+ */
+ local_irq_enable();
+
+ switch ( type )
+ {
+ case X86_ET_HW_EXC:
+ case X86_ET_PRIV_SW_EXC:
+ case X86_ET_SW_EXC:
+ switch ( vec )
+ {
+ case X86_EXC_PF: handle_PF(regs, fi->edata); break;
+ case X86_EXC_GP: do_general_protection(regs); break;
+ case X86_EXC_UD: do_invalid_op(regs); break;
+ case X86_EXC_NM: do_device_not_available(regs); break;
+ case X86_EXC_BP: do_int3(regs); break;
+ case X86_EXC_DB: handle_DB(regs, fi->edata); break;
+ case X86_EXC_CP: do_entry_CP(regs); break;
+
+ case X86_EXC_DE:
+ case X86_EXC_OF:
+ case X86_EXC_BR:
+ case X86_EXC_NP:
+ case X86_EXC_SS:
+ case X86_EXC_MF:
+ case X86_EXC_AC:
+ case X86_EXC_XM:
+ do_trap(regs);
+ break;
+ default:
+ goto fatal;
+ }
+ break;
+
+ default:
+ goto fatal;
+ }
+
+ return;
+
+ fatal:
fatal_trap(regs, false);
}
diff --git a/xen/arch/x86/x86_64/entry-fred.S b/xen/arch/x86/x86_64/entry-fred.S
index 3c3320df22cb..a1ff9a4a9747 100644
--- a/xen/arch/x86/x86_64/entry-fred.S
+++ b/xen/arch/x86/x86_64/entry-fred.S
@@ -15,9 +15,20 @@ FUNC(entry_FRED_R3, 4096)
mov %rsp, %rdi
call entry_from_pv
+#ifdef CONFIG_PV
+ GET_STACK_END(14)
+ movq STACK_CPUINFO_FIELD(current_vcpu)(%r14), %rbx
+
+ jmp test_all_events
+#else
+ BUG /* Not Reached */
+#endif
+END(entry_FRED_R3)
+
+FUNC(eretu_exit_to_guest)
POP_GPRS
eretu
-END(entry_FRED_R3)
+END(eretu_exit_to_guest)
/* The Ring0 entrypoint is at Ring3 + 0x100. */
.org entry_FRED_R3 + 0x100, 0xcc
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index ca446c6ff0ce..0692163faa44 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -63,7 +63,7 @@ UNLIKELY_END(syscall_no_callback)
/* Conditionally clear DF */
and %esi, UREGS_eflags(%rsp)
/* %rbx: struct vcpu */
-test_all_events:
+LABEL(test_all_events, 0)
ASSERT_NOT_IN_ATOMIC
cli # tests must not race interrupts
/*test_softirqs:*/
@@ -152,6 +152,8 @@ END(switch_to_kernel)
FUNC_LOCAL(restore_all_guest)
ASSERT_INTERRUPTS_DISABLED
+ ALTERNATIVE "", "jmp eretu_exit_to_guest", X86_FEATURE_XEN_FRED
+
/* Stash guest SPEC_CTRL value while we can read struct vcpu. */
mov VCPU_arch_msrs(%rbx), %rdx
mov VCPUMSR_spec_ctrl_raw(%rdx), %r15d
--
2.39.5