From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
David Hildenbrand <david@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Juergen Gross <jgross@suse.com>, Deep Shah <sdeep@vmware.com>,
VMware Inc <pv-drivers@vmware.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.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>,
linux-kernel@vger.kernel.org
Subject: [PATCH v10 07/11] x86/tdx: Add HLT support for TDX guest
Date: Fri, 8 Oct 2021 22:37:43 -0700 [thread overview]
Message-ID: <20211009053747.1694419-8-sathyanarayanan.kuppuswamy@linux.intel.com> (raw)
In-Reply-To: <20211009053747.1694419-1-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 v9:
* None
Changes since v8:
* Moved tdx_halt() comments near variable declaration.
Changes since v7:
* Added section title to spec reference in commit log and comments.
* Added extra comments as per review suggestion.
Changes since v6:
* None
Changes since v5:
* Replaced sti with STI in commit log and comments.
* Added comments for _tdx_hypercall() usage in _tdx_halt().
* Added new helper function _tdx_halt() to contain common
code between tdx_halt() and tdx_safe_halt().
* Renamed tdg_->tdx_.
* Removed BUG_ON() and used WARN_ONCE() for HLT emulation
failure.
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 | 30 ++++++++++++++++
arch/x86/kernel/tdx.c | 75 ++++++++++++++++++++++++++++++++++++++--
2 files changed, 103 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/tdcall.S b/arch/x86/kernel/tdcall.S
index c7a5b8d79552..4b1fd1dd2ab5 100644
--- a/arch/x86/kernel/tdcall.S
+++ b/arch/x86/kernel/tdcall.S
@@ -36,6 +36,9 @@
*/
#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).
@@ -235,6 +238,33 @@ 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.
+ *
+ * This 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 1ef979008fe8..c05e8824e5e0 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -5,6 +5,7 @@
#define pr_fmt(fmt) "tdx: " fmt
#include <asm/tdx.h>
+#include <asm/vmx.h>
/* TDX Module call Leaf IDs */
#define TDX_GET_VEINFO 3
@@ -53,6 +54,62 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14,
return out->r10;
}
+static __cpuidle void _tdx_halt(const bool irq_disabled, const bool do_sti)
+{
+ u64 ret;
+
+ /*
+ * Emulate HLT operation via hypercall. More info about ABI
+ * can be found in TDX Guest-Host-Communication Interface
+ * (GHCI), sec 3.8 TDG.VP.VMCALL<Instruction.HLT>.
+ *
+ * The VMM uses the "IRQ disabled" param to understand IRQ
+ * enabled status (RFLAGS.IF) of TD guest and determine
+ * whether or not it should schedule the halted vCPU if an
+ * IRQ becomes pending. E.g. if IRQs are disabled the VMM
+ * can keep the vCPU in virtual HLT, even if an IRQ is
+ * pending, without hanging/breaking the guest.
+ *
+ * do_sti parameter is used by __tdx_hypercall() to decide
+ * whether to call STI instruction before executing TDCALL
+ * instruction.
+ */
+ ret = _tdx_hypercall(EXIT_REASON_HLT, irq_disabled, 0, 0, do_sti, NULL);
+
+ /*
+ * Use WARN_ONCE() to report the failure. Since tdx_*halt() calls
+ * are also used in pv_ops, #VE error handler cannot be used to
+ * report the failure.
+ */
+ WARN_ONCE(ret, "HLT instruction emulation failed\n");
+}
+
+static __cpuidle void tdx_halt(void)
+{
+ /*
+ * Non safe halt is mainly used in CPU offlining and
+ * the guest will stay in halt state. So, STI
+ * instruction call is not required (set do_sti as
+ * false).
+ */
+ const bool irq_disabled = irqs_disabled();
+ const bool do_sti = false;
+
+ _tdx_halt(irq_disabled, do_sti);
+}
+
+static __cpuidle void tdx_safe_halt(void)
+{
+ /*
+ * Since STI instruction will be called in __tdx_hypercall()
+ * set irq_disabled as false.
+ */
+ const bool irq_disabled = false;
+ const bool do_sti = true;
+
+ _tdx_halt(irq_disabled, do_sti);
+}
+
bool tdx_get_ve_info(struct ve_info *ve)
{
struct tdx_module_output out;
@@ -84,8 +141,19 @@ bool tdx_get_ve_info(struct ve_info *ve)
bool tdx_handle_virtualization_exception(struct pt_regs *regs,
struct ve_info *ve)
{
- pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
- return false;
+ switch (ve->exit_reason) {
+ case EXIT_REASON_HLT:
+ tdx_halt();
+ break;
+ default:
+ pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
+ return false;
+ }
+
+ /* After successful #VE handling, move the IP */
+ regs->ip += ve->instr_len;
+
+ return true;
}
void __init tdx_early_init(void)
@@ -95,5 +163,8 @@ void __init tdx_early_init(void)
setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
+ pv_ops.irq.safe_halt = tdx_safe_halt;
+ pv_ops.irq.halt = tdx_halt;
+
pr_info("Guest initialized\n");
}
--
2.25.1
next prev parent reply other threads:[~2021-10-09 5:38 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-09 5:37 [PATCH v10 00/11] Add TDX Guest Support (Initial support) Kuppuswamy Sathyanarayanan
2021-10-09 5:37 ` [PATCH v10 01/11] x86/paravirt: Move halt paravirt calls under CONFIG_PARAVIRT Kuppuswamy Sathyanarayanan
2021-10-15 16:59 ` David Hildenbrand
2021-10-09 5:37 ` [PATCH v10 02/11] x86/tdx: Introduce INTEL_TDX_GUEST config option Kuppuswamy Sathyanarayanan
2021-10-11 18:19 ` Josh Poimboeuf
2021-10-11 18:38 ` Andi Kleen
2021-10-11 18:47 ` Kuppuswamy, Sathyanarayanan
2021-10-09 5:37 ` [PATCH v10 03/11] x86/cpufeatures: Add TDX Guest CPU feature Kuppuswamy Sathyanarayanan
2021-10-13 8:18 ` Borislav Petkov
2021-10-13 13:32 ` Sathyanarayanan Kuppuswamy
2021-10-13 19:42 ` Josh Poimboeuf
2021-10-13 23:19 ` Thomas Gleixner
2021-10-14 0:25 ` Josh Poimboeuf
2021-10-14 7:57 ` Borislav Petkov
[not found] ` <1a6220a5-3abd-dea1-4b2f-2acade311236@linux.intel.com>
2021-10-18 21:59 ` Borislav Petkov
2021-10-18 22:04 ` Sathyanarayanan Kuppuswamy
2021-10-13 20:44 ` Thomas Gleixner
2021-10-13 21:05 ` Sathyanarayanan Kuppuswamy
2021-10-13 21:35 ` Thomas Gleixner
2021-10-13 21:07 ` Borislav Petkov
2021-10-13 21:25 ` Thomas Gleixner
2021-10-13 21:37 ` Borislav Petkov
2021-10-13 22:28 ` Sathyanarayanan Kuppuswamy
2021-10-13 23:02 ` Thomas Gleixner
2021-10-14 17:28 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 04/11] x86/tdx: Add TDX support to intel_cc_platform_has() Kuppuswamy Sathyanarayanan
2021-10-13 15:57 ` Borislav Petkov
2021-10-14 7:12 ` Thomas Gleixner
2021-10-14 17:31 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 05/11] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Kuppuswamy Sathyanarayanan
2021-10-14 7:28 ` Thomas Gleixner
2021-10-15 0:19 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 06/11] x86/traps: Add #VE support for TDX guest Kuppuswamy Sathyanarayanan
2021-10-14 8:30 ` Thomas Gleixner
2021-10-17 2:45 ` Sathyanarayanan Kuppuswamy
2021-10-17 3:18 ` Dave Hansen
2021-10-17 3:49 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` Kuppuswamy Sathyanarayanan [this message]
2021-10-14 9:30 ` [PATCH v10 07/11] x86/tdx: Add HLT " Thomas Gleixner
2021-10-15 1:33 ` Sathyanarayanan Kuppuswamy
2021-10-15 15:03 ` Sean Christopherson
2021-10-09 5:37 ` [PATCH v10 08/11] x86/tdx: Wire up KVM hypercalls Kuppuswamy Sathyanarayanan
2021-10-14 10:21 ` Thomas Gleixner
2021-10-15 3:03 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 09/11] x86/tdx: Add MSR support for TDX guest Kuppuswamy Sathyanarayanan
2021-10-09 5:37 ` [PATCH v10 10/11] x86/tdx: Don't write CSTAR MSR on Intel Kuppuswamy Sathyanarayanan
2021-10-14 10:47 ` Thomas Gleixner
2021-10-14 13:47 ` Andi Kleen
2021-10-14 14:27 ` Thomas Gleixner
2021-10-09 5:37 ` [PATCH v10 11/11] x86/tdx: Handle CPUID via #VE Kuppuswamy Sathyanarayanan
2021-10-14 12:01 ` Thomas Gleixner
2021-10-14 13:25 ` Dave Hansen
2021-10-09 7:38 ` [PATCH v10 00/11] Add TDX Guest Support (Initial support) Borislav Petkov
2021-10-09 20:56 ` Kuppuswamy, Sathyanarayanan
2021-10-11 13:03 ` Borislav Petkov
2021-10-11 16:33 ` Dave Hansen
2021-10-11 16:48 ` Dave Hansen
2021-10-11 17:04 ` Borislav Petkov
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