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Message-ID: <20250429151808.GJ4198@noisy.programming.kicks-ass.net>
Date: Tue, 29 Apr 2025 17:18:08 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Michael Kelley <mhklinux@...look.com>
Cc: "x86@...nel.org" <x86@...nel.org>,
"kys@...rosoft.com" <kys@...rosoft.com>,
"haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
"decui@...rosoft.com" <decui@...rosoft.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"hpa@...or.com" <hpa@...or.com>,
"jpoimboe@...nel.org" <jpoimboe@...nel.org>,
"pawan.kumar.gupta@...ux.intel.com" <pawan.kumar.gupta@...ux.intel.com>,
"seanjc@...gle.com" <seanjc@...gle.com>,
"pbonzini@...hat.com" <pbonzini@...hat.com>,
"ardb@...nel.org" <ardb@...nel.org>,
"kees@...nel.org" <kees@...nel.org>, Arnd Bergmann <arnd@...db.de>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
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"ojeda@...nel.org" <ojeda@...nel.org>
Subject: Re: [PATCH 4/6] x86,hyperv: Clean up hv_do_hypercall()
On Mon, Apr 21, 2025 at 06:27:57PM +0000, Michael Kelley wrote:
> > @@ -483,14 +484,16 @@ static void __init ms_hyperv_init_platfo
> > ms_hyperv.shared_gpa_boundary =
> > BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);
> >
> > - hyperv_paravisor_present = !!ms_hyperv.paravisor_present;
> > -
> > pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
> > ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
> >
> >
> > if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
> > static_branch_enable(&isolation_type_snp);
> > +#if defined(CONFIG_AMD_MEM_ENCRYPT) && defined(CONFIG_HYPERV)
> > + if (!ms_hyperv.paravisor_present)
> > + static_call_update(hv_hypercall, hv_snp_hypercall);
> > +#endif
>
> This #ifdef (and one below for TDX) are really ugly. They could be avoided by adding
> stubs for hv_snp_hypercall() and hv_tdx_hypercall(), and making the hv_hypercall static
> call exist even when !CONFIG_HYPERV (and for 32-bit builds). Or is there a reason to
> not do that?
>
> > } else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX) {
> > static_branch_enable(&isolation_type_tdx);
> >
> > @@ -498,6 +501,9 @@ static void __init ms_hyperv_init_platfo
> > ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;
> >
> > if (!ms_hyperv.paravisor_present) {
> > +#if defined(CONFIG_INTEL_TDX_GUEST) && defined(CONFIG_HYPERV)
> > + static_call_update(hv_hypercall, hv_tdx_hypercall);
> > +#endif
> > /*
> > * Mark the Hyper-V TSC page feature as disabled
> > * in a TDX VM without paravisor so that the
> >
> >
I've ended up with the below.. I thought it a waste to make all that
stuff available to 32bit and !HYPERV.
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -392,6 +392,7 @@ u64 hv_snp_hypercall(u64 control, u64 pa
#else
static inline void hv_ghcb_msr_write(u64 msr, u64 value) {}
static inline void hv_ghcb_msr_read(u64 msr, u64 *value) {}
+u64 hv_snp_hypercall(u64 control, u64 param1, u64 param2) {}
#endif /* CONFIG_AMD_MEM_ENCRYPT */
#ifdef CONFIG_INTEL_TDX_GUEST
@@ -441,6 +442,7 @@ u64 hv_tdx_hypercall(u64 control, u64 pa
#else
static inline void hv_tdx_msr_write(u64 msr, u64 value) {}
static inline void hv_tdx_msr_read(u64 msr, u64 *value) {}
+u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2) {}
#endif /* CONFIG_INTEL_TDX_GUEST */
#if defined(CONFIG_AMD_MEM_ENCRYPT) || defined(CONFIG_INTEL_TDX_GUEST)
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -39,6 +39,10 @@ static inline unsigned char hv_get_nmi_r
return 0;
}
+extern u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
+extern u64 hv_snp_hypercall(u64 control, u64 param1, u64 param2);
+extern u64 hv_std_hypercall(u64 control, u64 param1, u64 param2);
+
#if IS_ENABLED(CONFIG_HYPERV)
extern void *hv_hypercall_pg;
@@ -48,10 +52,6 @@ bool hv_isolation_type_snp(void);
bool hv_isolation_type_tdx(void);
#ifdef CONFIG_X86_64
-extern u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
-extern u64 hv_snp_hypercall(u64 control, u64 param1, u64 param2);
-extern u64 hv_std_hypercall(u64 control, u64 param1, u64 param2);
-
DECLARE_STATIC_CALL(hv_hypercall, hv_std_hypercall);
#endif
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -287,9 +287,14 @@ static void __init x86_setup_ops_for_tsc
#ifdef CONFIG_X86_64
DEFINE_STATIC_CALL(hv_hypercall, hv_std_hypercall);
EXPORT_STATIC_CALL_TRAMP_GPL(hv_hypercall);
+#define hypercall_update(hc) static_call_update(hv_hypercall, hc)
#endif
#endif /* CONFIG_HYPERV */
+#ifndef hypercall_update
+#define hypercall_update(hc) (void)hc
+#endif
+
static uint32_t __init ms_hyperv_platform(void)
{
u32 eax;
@@ -490,10 +495,8 @@ static void __init ms_hyperv_init_platfo
if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
static_branch_enable(&isolation_type_snp);
-#if defined(CONFIG_AMD_MEM_ENCRYPT) && defined(CONFIG_HYPERV)
if (!ms_hyperv.paravisor_present)
- static_call_update(hv_hypercall, hv_snp_hypercall);
-#endif
+ hypercall_update(hv_snp_hypercall);
} else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX) {
static_branch_enable(&isolation_type_tdx);
@@ -501,9 +504,7 @@ static void __init ms_hyperv_init_platfo
ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;
if (!ms_hyperv.paravisor_present) {
-#if defined(CONFIG_INTEL_TDX_GUEST) && defined(CONFIG_HYPERV)
- static_call_update(hv_hypercall, hv_tdx_hypercall);
-#endif
+ hypercall_update(hv_tdx_hypercall);
/*
* Mark the Hyper-V TSC page feature as disabled
* in a TDX VM without paravisor so that the
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