[PATCH v1 08/11] x86/tdx: Add HLT support for TDX guest

Kuppuswamy Sathyanarayanan
2021-06-02T02:22:10Z

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

Per Guest-Host-Communication Interface (GHCI) for Intel Trust
Domain Extensions (Intel TDX) specification, sec 3.8,
TDVMCALL[Instruction.HLT] provides HLT operation. Use it to implement
halt() and safe_halt() paravirtualization calls.

The same TDX hypercall is used to handle #VE exception due to
EXIT_REASON_HLT.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
arch/x86/kernel/tdx.c | 50 +++++++++++++++++++++++++++++++++++++------
1 file changed, 43 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 527d2638ddae..76b71bf56b81 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -88,6 +88,33 @@ static void tdg_get_info(void)
td_info.attributes = out.rdx;
}

+static __cpuidle void tdg_halt(void)
+{
+ u64 ret;
+
+ ret = __tdx_hypercall(EXIT_REASON_HLT, irqs_disabled(), 0, 0, 0, NULL);
+
+ /* It should never fail */
+ BUG_ON(ret);
+}
+
+static __cpuidle void tdg_safe_halt(void)
+{
+ u64 ret;
+
+ /*
+ * Enable interrupts next to the TDVMCALL to avoid
+ * performance degradation.
+ */
+ local_irq_enable();
+
+ /* IRQ is enabled, So set R12 as 0 */
+ ret = __tdx_hypercall(EXIT_REASON_HLT, 0, 0, 0, 0, NULL);
+
+ /* It should never fail */
+ BUG_ON(ret);
+}
+
unsigned long tdg_get_ve_info(struct ve_info *ve)
{
u64 ret;
@@ -114,13 +141,19 @@ unsigned long tdg_get_ve_info(struct ve_info *ve)
int tdg_handle_virtualization_exception(struct pt_regs *regs,
struct ve_info *ve)
{
- /*
- * TODO: Add handler support for various #VE exit
- * reasons. It will be added by other patches in
- * the series.
- */
- pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
- return -EFAULT;
+ switch (ve->exit_reason) {
+ case EXIT_REASON_HLT:
+ tdg_halt();
+ break;
+ default:
+ pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
+ return -EFAULT;
+ }
+
+ /* After successful #VE handling, move the IP */
+ regs->ip += ve->instr_len;
+
+ return 0;
}

void __init tdx_early_init(void)
@@ -132,5 +165,8 @@ void __init tdx_early_init(void)

tdg_get_info();

+ pv_ops.irq.safe_halt = tdg_safe_halt;
+ pv_ops.irq.halt = tdg_halt;
+
pr_info("TDX guest is initialized\n");
}
--
2.25.1