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From: Kuppuswamy Sathyanarayanan  <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>
Cc: Peter H Anvin <hpa@zytor.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	Kirill Shutemov <kirill.shutemov@linux.intel.com>,
	Sean Christopherson <seanjc@google.com>,
	Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v5 08/12] x86/tdx: Add HLT support for TDX guest
Date: Wed,  4 Aug 2021 11:13:25 -0700	[thread overview]
Message-ID: <20210804181329.2899708-9-sathyanarayanan.kuppuswamy@linux.intel.com> (raw)
In-Reply-To: <20210804181329.2899708-1-sathyanarayanan.kuppuswamy@linux.intel.com>

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>
---

Changes since v4:
 * Added exception for EXIT_REASON_HLT in __tdx_hypercall() to
   enable interrupts using sti.

Changes since v3:
 * None

 arch/x86/kernel/tdcall.S | 29 +++++++++++++++++++++++
 arch/x86/kernel/tdx.c    | 51 ++++++++++++++++++++++++++++++++++------
 2 files changed, 73 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/tdcall.S b/arch/x86/kernel/tdcall.S
index c9c91c1bf99d..9df94f87465d 100644
--- a/arch/x86/kernel/tdcall.S
+++ b/arch/x86/kernel/tdcall.S
@@ -40,6 +40,9 @@
  */
 #define tdcall .byte 0x66,0x0f,0x01,0xcc
 
+/* HLT TDVMCALL sub-function ID */
+#define EXIT_REASON_HLT			12
+
 /*
  * __tdx_module_call()  - Helper function used by TDX guests to request
  * services from the TDX module (does not include VMM services).
@@ -240,6 +243,32 @@ SYM_FUNC_START(__tdx_hypercall)
 
 	movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx
 
+	/*
+	 * For the idle loop STI needs to be called directly before
+	 * the TDCALL that enters idle (EXIT_REASON_HLT case). STI
+	 * enables interrupts only one instruction later. If there
+	 * are any instructions between the STI and the TDCALL for
+	 * HLT then an interrupt could happen in that time, but the
+	 * code would go back to sleep afterwards, which can cause
+	 * longer delays. There leads to significant difference in
+	 * network performance benchmarks. So add a special case for
+	 * EXIT_REASON_HLT to trigger sti before TDCALL. But this
+	 * change is not required for all HLT cases. So use R15
+	 * register value to identify the case which needs sti. So,
+	 * if R11 is EXIT_REASON_HLT and R15 is 1, then call sti
+	 * before TDCALL instruction. Note that R15 register is not
+	 * required by TDCALL ABI when triggering the hypercall for
+	 * EXIT_REASON_HLT case. So use it in software to select the
+	 * sti case.
+	 */
+	cmpl $EXIT_REASON_HLT, %r11d
+	jne skip_sti
+	cmpl $1, %r15d
+	jne skip_sti
+	/* Set R15 register to 0, it is unused in EXIT_REASON_HLT case */
+	xor %r15, %r15
+	sti
+skip_sti:
 	tdcall
 
 	/* Restore output pointer to R9 */
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 6169f9c740b2..bdd041c4c509 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -7,6 +7,7 @@
 #include <linux/protected_guest.h>
 
 #include <asm/tdx.h>
+#include <asm/vmx.h>
 
 /* TDX Module call Leaf IDs */
 #define TDINFO				1
@@ -76,6 +77,33 @@ 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, 1, NULL);
+
+	/* It should never fail */
+	BUG_ON(ret);
+}
+
 unsigned long tdg_get_ve_info(struct ve_info *ve)
 {
 	u64 ret;
@@ -102,13 +130,19 @@ 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)
@@ -120,5 +154,8 @@ 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("Guest initialized\n");
 }
-- 
2.25.1


  parent reply	other threads:[~2021-08-04 18:15 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-04 18:13 [PATCH v5 00/12] Add TDX Guest Support (Initial support) Kuppuswamy Sathyanarayanan
2021-08-04 18:13 ` [PATCH v5 01/12] x86/paravirt: Move halt paravirt calls under CONFIG_PARAVIRT Kuppuswamy Sathyanarayanan
2021-08-12  7:18   ` Borislav Petkov
2021-08-12 17:17     ` Kuppuswamy, Sathyanarayanan
2021-08-17 12:50     ` Juergen Gross
2021-08-17 13:16       ` Kuppuswamy, Sathyanarayanan
2021-08-17 13:28         ` Juergen Gross
2021-08-17 13:39           ` Kuppuswamy, Sathyanarayanan
2021-08-17 13:47             ` Juergen Gross
2021-08-17 13:50               ` Kuppuswamy, Sathyanarayanan
2021-08-04 18:13 ` [PATCH v5 02/12] x86/tdx: Introduce INTEL_TDX_GUEST config option Kuppuswamy Sathyanarayanan
2021-08-04 18:13 ` [PATCH v5 03/12] x86/cpufeatures: Add TDX Guest CPU feature Kuppuswamy Sathyanarayanan
2021-08-12  7:39   ` Borislav Petkov
2021-08-04 18:13 ` [PATCH v5 04/12] x86/tdx: Add protected guest support for TDX guest Kuppuswamy Sathyanarayanan
2021-08-04 21:59   ` Sean Christopherson
2021-08-04 22:03     ` Dave Hansen
2021-08-04 22:26       ` Kuppuswamy, Sathyanarayanan
2021-08-04 22:42         ` Sean Christopherson
2021-08-04 23:00           ` Kuppuswamy, Sathyanarayanan
2021-08-12  7:53             ` Borislav Petkov
2021-08-12 17:18               ` Kuppuswamy, Sathyanarayanan
2021-08-20 14:28                 ` Borislav Petkov
2021-08-20 16:42                   ` Kuppuswamy, Sathyanarayanan
2021-08-20 16:59                     ` Borislav Petkov
2021-08-20 17:11                       ` Kuppuswamy, Sathyanarayanan
2021-08-04 18:13 ` [PATCH v5 05/12] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Kuppuswamy Sathyanarayanan
2021-08-20 15:16   ` Borislav Petkov
2021-08-04 18:13 ` [PATCH v5 06/12] x86/tdx: Get TD execution environment information via TDINFO Kuppuswamy Sathyanarayanan
2021-08-04 22:38   ` Sean Christopherson
2021-08-20 17:13   ` Borislav Petkov
2021-08-20 17:31     ` Kuppuswamy, Sathyanarayanan
2021-08-20 17:35       ` Borislav Petkov
2021-08-20 18:29         ` Kuppuswamy, Sathyanarayanan
2021-08-20 18:58           ` Andi Kleen
2021-08-20 19:01             ` Kuppuswamy, Sathyanarayanan
2021-08-04 18:13 ` [PATCH v5 07/12] x86/traps: Add #VE support for TDX guest Kuppuswamy Sathyanarayanan
2021-08-24 10:17   ` Borislav Petkov
2021-08-24 17:32     ` Kuppuswamy, Sathyanarayanan
2021-08-24 17:36       ` Dave Hansen
2021-08-24 17:46       ` Borislav Petkov
2021-09-02 15:24         ` Kuppuswamy, Sathyanarayanan
2021-09-03 10:17           ` Borislav Petkov
2021-08-04 18:13 ` Kuppuswamy Sathyanarayanan [this message]
2021-08-24 16:10   ` [PATCH v5 08/12] x86/tdx: Add HLT " Borislav Petkov
2021-08-24 17:06     ` Sean Christopherson
2021-08-24 17:25       ` Andi Kleen
2021-08-24 17:27       ` Borislav Petkov
2021-08-24 17:47         ` Sean Christopherson
2021-08-24 17:50           ` Borislav Petkov
2021-08-31 20:49         ` Kuppuswamy, Sathyanarayanan
2021-09-01  7:42           ` Borislav Petkov
2021-08-24 18:18       ` Kuppuswamy, Sathyanarayanan
2021-08-24 18:28         ` Andi Kleen
2021-08-24 17:35     ` Kuppuswamy, Sathyanarayanan
2021-08-24 17:48       ` Borislav Petkov
2021-08-04 18:13 ` [PATCH v5 09/12] x86/tdx: Wire up KVM hypercalls Kuppuswamy Sathyanarayanan
2021-08-24 16:34   ` Borislav Petkov
2021-08-24 18:11     ` Kuppuswamy, Sathyanarayanan
2021-08-24 18:29       ` Borislav Petkov
2021-08-24 19:11         ` Kuppuswamy, Sathyanarayanan
2021-08-24 19:39           ` Borislav Petkov
2021-08-04 18:13 ` [PATCH v5 10/12] x86/tdx: Add MSR support for TDX guest Kuppuswamy Sathyanarayanan
2021-08-24 16:55   ` Borislav Petkov
2021-08-24 18:12     ` Kuppuswamy, Sathyanarayanan
2021-08-04 18:13 ` [PATCH v5 11/12] x86/tdx: Don't write CSTAR MSR on Intel Kuppuswamy Sathyanarayanan
2021-08-04 18:31   ` Sean Christopherson
2021-08-04 21:03     ` Kuppuswamy, Sathyanarayanan
2021-08-04 21:44       ` Sean Christopherson
2021-08-04 21:48       ` Dave Hansen
2021-08-04 22:23         ` Kuppuswamy, Sathyanarayanan
2021-08-04 18:13 ` [PATCH v5 12/12] x86/tdx: Handle CPUID via #VE Kuppuswamy Sathyanarayanan
2021-08-24 17:48   ` Borislav Petkov

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