[PATCH 21/36] x86/tdx: Remove TDX_HCALL_ISSUE_STI
From: Peter Zijlstra <peterz@infradead.org>
Date: 2022-06-08 14:49:55
Also in:
linux-acpi, linux-alpha, linux-arch, linux-arm-msm, linux-clk, linux-m68k, linux-mips, linux-omap, linux-perf-users, linux-pm, linux-riscv, linux-s390, linux-sh, linux-tegra, linux-um, lkml, rcu, sparclinux, virtualization, xen-devel
, Arnd Bergmann [off-list ref], ulli.kroll@googlemail.com, vgupta@kernel.org, linux-clk@vger.kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, rcu@vger.kernel.org, bp@alien8.de, bcain@quicinc.com, tsbogend@alpha.franken.de, linux-parisc@vger.kernel.org, sudeep.holla@arm.com, shawnguo@kernel.org, davem@davemloft.net, kirill.shutemov@linux.intel.com, dalias@libc.org, tony@atomide.com, amakhalov@vmware.com, bjorn.andersson@linaro.org, hpa@zytor.com, sparclinux@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-riscv@lists.infradead.org, Isaku Yamahata [off-list ref], anton.ivanov@cambridgegreys.com, jonas@southpole.se, yury.norov@gmail.com, richard@nod.at, x86@kernel.org, linux@armlinux.org.uk, mingo@redhat.com, aou@eecs.berkeley.edu, paulmck@kernel.org, hca@linux.ibm.com, stefan.kristiansson@saunalahti.fi, openrisc@lists.librecores.org, paul.walmsley@sifive.com, linux-tegra@vger.kernel.org, namhyung@kernel.org, andriy.shevchenko@linux.intel.com, jpoimboe@kernel.or g, jgross@suse.com, monstr@monstr.eu, linux-mips@vger.kernel.org, palmer@dabbelt.com, anup@brainfault.org, ink@jurassic.park.msu.ru, johannes@sipsolutions.net, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" [off-list ref] Now that arch_cpu_idle() is expected to return with IRQs disabled, avoid the useless STI/CLI dance. Per the specs this is supposed to work, but nobody has yet relied up this behaviour so broken implementations are possible. Cc: Isaku Yamahata <redacted> Cc: kirill.shutemov@linux.intel.com Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/x86/coco/tdx/tdcall.S | 13 ------------- arch/x86/coco/tdx/tdx.c | 23 ++++------------------- arch/x86/include/asm/shared/tdx.h | 1 - 3 files changed, 4 insertions(+), 33 deletions(-)
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S@@ -139,19 +139,6 @@ 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 instruction enables - * interrupts only one instruction later. If there is a window between - * STI and the instruction that emulates the HALT state, there is a - * chance for interrupts to happen in this window, which can delay the - * HLT operation indefinitely. Since this is the not the desired - * result, conditionally call STI before TDCALL. - */ - testq $TDX_HCALL_ISSUE_STI, %rsi - jz .Lskip_sti - sti -.Lskip_sti: tdcall /* --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c
@@ -124,7 +124,7 @@ static u64 get_cc_mask(void) return BIT_ULL(gpa_width - 1); } -static u64 __cpuidle __halt(const bool irq_disabled, const bool do_sti) +static u64 __cpuidle __halt(const bool irq_disabled) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD,
@@ -144,20 +144,14 @@ static u64 __cpuidle __halt(const bool i * can keep the vCPU in virtual HLT, even if an IRQ is * pending, without hanging/breaking the guest. */ - return __tdx_hypercall(&args, do_sti ? TDX_HCALL_ISSUE_STI : 0); + return __tdx_hypercall(&args, 0); } static bool handle_halt(void) { - /* - * Since non safe halt is mainly used in CPU offlining - * and the guest will always stay in the halt state, don't - * call the STI instruction (set do_sti as false). - */ const bool irq_disabled = irqs_disabled(); - const bool do_sti = false; - if (__halt(irq_disabled, do_sti)) + if (__halt(irq_disabled)) return false; return true;
@@ -165,22 +159,13 @@ static bool handle_halt(void) void __cpuidle tdx_safe_halt(void) { - /* - * For do_sti=true case, __tdx_hypercall() function enables - * interrupts using the STI instruction before the TDCALL. So - * set irq_disabled as false. - */ const bool irq_disabled = false; - const bool do_sti = true; /* * Use WARN_ONCE() to report the failure. */ - if (__halt(irq_disabled, do_sti)) + if (__halt(irq_disabled)) WARN_ONCE(1, "HLT instruction emulation failed\n"); - - /* XXX I can't make sense of what @do_sti actually does */ - raw_local_irq_disable(); } static bool read_msr(struct pt_regs *regs) --- a/arch/x86/include/asm/shared/tdx.h +++ b/arch/x86/include/asm/shared/tdx.h
@@ -8,7 +8,6 @@ #define TDX_HYPERCALL_STANDARD 0 #define TDX_HCALL_HAS_OUTPUT BIT(0) -#define TDX_HCALL_ISSUE_STI BIT(1) #define TDX_CPUID_LEAF_ID 0x21 #define TDX_IDENT "IntelTDX "