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AJvYcCX+RnGaKeenSUVPcnIzBFmQHhdvmUl8zEF8np4PtdNUHDYFcH44Gnr9i5jnkTry/kqfr6fAvgMSgziPLNI=@vger.kernel.org X-Gm-Message-State: AOJu0YzXs+fOj1tun41suQ72hawfLV8GrjcjVrU2ZX9+FOcP+Cu/HEwQ kiiDfyQLzRaZ394pz2EYphDdzQuZ72xJfkMbcmxGKageaTf7PQu/o7Ji9MQVauXo4rbhfgZy5Ze 7k0FTPA== X-Received: from plsl9.prod.google.com ([2002:a17:903:2449:b0:2ae:3d76:eb1b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:1968:b0:2ae:8062:8362 with SMTP id d9443c01a7336-2ae82266d9fmr111476405ad.0.1773069857431; Mon, 09 Mar 2026 08:24:17 -0700 (PDT) Date: Mon, 9 Mar 2026 08:24:16 -0700 In-Reply-To: <9C6FC4E7-DF8A-4583-93A8-3B82806D11CD@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251026201911.505204-1-xin@zytor.com> <20251026201911.505204-7-xin@zytor.com> <20260130134644.GUaXy2RNbwEaRSgLUN@fat_crate.local> <9C6FC4E7-DF8A-4583-93A8-3B82806D11CD@zytor.com> Message-ID: Subject: Re: [PATCH v9 06/22] x86/cea: Export __this_cpu_ist_top_va() to KVM From: Sean Christopherson To: Xin Li Cc: Borislav Petkov , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, pbonzini@redhat.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, chao.gao@intel.com, hch@infradead.org, sohil.mehta@intel.com Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Fri, Mar 06, 2026, Xin Li wrote: > > On Jan 30, 2026, at 5:46=E2=80=AFAM, Borislav Petkov wro= te: > diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h > index 2bb65677c079..7eea65bfc838 100644 > --- a/arch/x86/include/asm/fred.h > +++ b/arch/x86/include/asm/fred.h > @@ -35,6 +35,13 @@ > =20 > #ifndef __ASSEMBLER__ > =20 > +enum fred_stack_level { > + FRED_STACK_LEVEL_0, > + FRED_STACK_LEVEL_1, > + FRED_STACK_LEVEL_2, > + FRED_STACK_LEVEL_3 Why bother with a layer of indirection and more enums? Just pivot on the M= SR index. > #ifdef CONFIG_X86_FRED > #include > #include > @@ -105,6 +112,8 @@ static __always_inline void fred_update_rsp0(void) > __this_cpu_write(fred_rsp0, rsp0); > } > } > + > +unsigned long this_cpu_fred_rsp(enum fred_stack_level lvl); > #else /* CONFIG_X86_FRED */ > static __always_inline unsigned long fred_event_data(struct pt_regs *reg= s) { return 0; } > static inline void cpu_init_fred_exceptions(void) { } > @@ -113,6 +122,7 @@ static inline void fred_complete_exception_setup(void= ) { } > static inline void fred_entry_from_kvm(unsigned int type, unsigned int v= ector) { } > static inline void fred_sync_rsp0(unsigned long rsp0) { } > static inline void fred_update_rsp0(void) { } > +static unsigned long this_cpu_fred_rsp(enum fred_stack_level lvl) { retu= rn 0; } > #endif /* CONFIG_X86_FRED */ > #endif /* !__ASSEMBLER__ */ > =20 > diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c > index 433c4a6f1773..363c53701012 100644 > --- a/arch/x86/kernel/fred.c > +++ b/arch/x86/kernel/fred.c > @@ -72,6 +72,23 @@ void cpu_init_fred_exceptions(void) > setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); > } > =20 > +unsigned long this_cpu_fred_rsp(enum fred_stack_level lvl) > +{ > + switch (lvl) { > + case FRED_STACK_LEVEL_0: > + return __this_cpu_read(fred_rsp0); > + case FRED_STACK_LEVEL_1: > + return __this_cpu_ist_top_va(ESTACK_DB); > + case FRED_STACK_LEVEL_2: > + return __this_cpu_ist_top_va(ESTACK_NMI); > + case FRED_STACK_LEVEL_3: > + return __this_cpu_ist_top_va(ESTACK_DF); > + default: > + BUG(); > + } > +} > +EXPORT_SYMBOL_FOR_MODULES(this_cpu_fred_rsp, "kvm-intel"); Meh, just do EXPORT_SYMBOL_FOR_KVM so that there's no export when KVM_X86= =3Dy|n. And it's possible AMD may need to grab the MSRs too. > + > /* Must be called after setup_cpu_entry_areas() */ > void cpu_init_fred_rsps(void) > { > @@ -87,7 +104,7 @@ void cpu_init_fred_rsps(void) > FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL)); > =20 > /* The FRED equivalents to IST stacks... */ > - wrmsrq(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(ESTACK_DB)); > - wrmsrq(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(ESTACK_NMI)); > - wrmsrq(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(ESTACK_DF)); > + wrmsrq(MSR_IA32_FRED_RSP1, this_cpu_fred_rsp(FRED_STACK_LEVEL_1)); > + wrmsrq(MSR_IA32_FRED_RSP2, this_cpu_fred_rsp(FRED_STACK_LEVEL_2)); > + wrmsrq(MSR_IA32_FRED_RSP3, this_cpu_fred_rsp(FRED_STACK_LEVEL_3)); > }