From: Juergen Gross <jgross@suse.com>
To: xen-devel@lists.xenproject.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org
Cc: Juergen Gross <jgross@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>, Deep Shah <sdeep@vmware.com>,
"VMware, Inc." <pv-drivers@vmware.com>
Subject: [PATCH v4 09/15] x86: add new features for paravirt patching
Date: Wed, 20 Jan 2021 14:55:49 +0100 [thread overview]
Message-ID: <20210120135555.32594-10-jgross@suse.com> (raw)
In-Reply-To: <20210120135555.32594-1-jgross@suse.com>
For being able to switch paravirt patching from special cased custom
code sequences to ALTERNATIVE handling some X86_FEATURE_* are needed
as new features. This enables to have the standard indirect pv call
as the default code and to patch that with the non-Xen custom code
sequence via ALTERNATIVE patching later.
Make sure paravirt patching is performed before alternative patching.
Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- add comment (Boris Petkov)
- no negative features (Boris Petkov)
V4:
- move paravirt_set_cap() to paravirt-spinlocks.c
---
arch/x86/include/asm/cpufeatures.h | 2 ++
arch/x86/include/asm/paravirt.h | 10 ++++++++++
arch/x86/kernel/alternative.c | 30 ++++++++++++++++++++++++++--
arch/x86/kernel/paravirt-spinlocks.c | 9 +++++++++
4 files changed, 49 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 84b887825f12..3ae8944b253a 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -238,6 +238,8 @@
#define X86_FEATURE_VMW_VMMCALL ( 8*32+19) /* "" VMware prefers VMMCALL hypercall instruction */
#define X86_FEATURE_SEV_ES ( 8*32+20) /* AMD Secure Encrypted Virtualization - Encrypted State */
#define X86_FEATURE_VM_PAGE_FLUSH ( 8*32+21) /* "" VM Page Flush MSR is supported */
+#define X86_FEATURE_PVUNLOCK ( 8*32+22) /* "" PV unlock function */
+#define X86_FEATURE_VCPUPREEMPT ( 8*32+23) /* "" PV vcpu_is_preempted function */
/* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
#define X86_FEATURE_FSGSBASE ( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 1e45b46fae84..8c354099d9c3 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -47,6 +47,10 @@ static inline u64 paravirt_steal_clock(int cpu)
return static_call(pv_steal_clock)(cpu);
}
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+void __init paravirt_set_cap(void);
+#endif
+
/* The paravirtualized I/O functions */
static inline void slow_down_io(void)
{
@@ -811,5 +815,11 @@ static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
{
}
#endif
+
+#ifndef CONFIG_PARAVIRT_SPINLOCKS
+static inline void paravirt_set_cap(void)
+{
+}
+#endif
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_PARAVIRT_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 0a904fb2678b..221acb2b868a 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -28,6 +28,7 @@
#include <asm/insn.h>
#include <asm/io.h>
#include <asm/fixmap.h>
+#include <asm/paravirt.h>
int __read_mostly alternatives_patched;
@@ -730,6 +731,33 @@ void __init alternative_instructions(void)
* patching.
*/
+ /*
+ * Paravirt patching and alternative patching can be combined to
+ * replace a function call with a short direct code sequence (e.g.
+ * by setting a constant return value instead of doing that in an
+ * external function).
+ * In order to make this work the following sequence is required:
+ * 1. set (artificial) features depending on used paravirt
+ * functions which can later influence alternative patching
+ * 2. apply paravirt patching (generally replacing an indirect
+ * function call with a direct one)
+ * 3. apply alternative patching (e.g. replacing a direct function
+ * call with a custom code sequence)
+ * Doing paravirt patching after alternative patching would clobber
+ * the optimization of the custom code with a function call again.
+ */
+ paravirt_set_cap();
+
+ /*
+ * First patch paravirt functions, such that we overwrite the indirect
+ * call with the direct call.
+ */
+ apply_paravirt(__parainstructions, __parainstructions_end);
+
+ /*
+ * Then patch alternatives, such that those paravirt calls that are in
+ * alternatives can be overwritten by their immediate fragments.
+ */
apply_alternatives(__alt_instructions, __alt_instructions_end);
#ifdef CONFIG_SMP
@@ -748,8 +776,6 @@ void __init alternative_instructions(void)
}
#endif
- apply_paravirt(__parainstructions, __parainstructions_end);
-
restart_nmi();
alternatives_patched = 1;
}
diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
index 4f75d0cf6305..9e1ea99ad9df 100644
--- a/arch/x86/kernel/paravirt-spinlocks.c
+++ b/arch/x86/kernel/paravirt-spinlocks.c
@@ -32,3 +32,12 @@ bool pv_is_native_vcpu_is_preempted(void)
return pv_ops.lock.vcpu_is_preempted.func ==
__raw_callee_save___native_vcpu_is_preempted;
}
+
+void __init paravirt_set_cap(void)
+{
+ if (!pv_is_native_spin_unlock())
+ setup_force_cpu_cap(X86_FEATURE_PVUNLOCK);
+
+ if (!pv_is_native_vcpu_is_preempted())
+ setup_force_cpu_cap(X86_FEATURE_VCPUPREEMPT);
+}
--
2.26.2
next prev parent reply other threads:[~2021-01-20 13:56 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 13:55 [PATCH v4 00/15] x86: major paravirt cleanup Juergen Gross
2021-01-20 13:55 ` [PATCH v4 01/15] static_call: Pull some static_call declarations to the type headers Juergen Gross
2021-01-20 13:55 ` [PATCH v4 02/15] x86/xen: use specific Xen pv interrupt entry for MCE Juergen Gross
2021-01-20 13:55 ` [PATCH v4 03/15] x86/xen: use specific Xen pv interrupt entry for DF Juergen Gross
2021-01-20 13:55 ` [PATCH v4 04/15] x86/pv: switch SWAPGS to ALTERNATIVE Juergen Gross
2021-01-20 13:55 ` [PATCH v4 05/15] x86/xen: drop USERGS_SYSRET64 paravirt call Juergen Gross
2021-01-20 13:55 ` [PATCH v4 06/15] x86: rework arch_local_irq_restore() to not use popf Juergen Gross
2021-01-20 13:55 ` [PATCH v4 07/15] x86/paravirt: switch time pvops functions to use static_call() Juergen Gross
2021-01-24 16:14 ` Michael Kelley
2021-02-01 19:48 ` Borislav Petkov
2021-01-20 13:55 ` [PATCH v4 08/15] x86/alternative: support "not feature" and ALTERNATIVE_TERNARY Juergen Gross
2021-01-20 13:55 ` Juergen Gross [this message]
2021-01-20 13:55 ` [PATCH v4 10/15] x86/paravirt: remove no longer needed 32-bit pvops cruft Juergen Gross
2021-01-20 13:55 ` [PATCH v4 11/15] x86/paravirt: simplify paravirt macros Juergen Gross
2021-01-20 13:55 ` [PATCH v4 12/15] x86/paravirt: switch iret pvops to ALTERNATIVE Juergen Gross
2021-01-20 13:55 ` [PATCH v4 13/15] x86/paravirt: add new macros PVOP_ALT* supporting pvops in ALTERNATIVEs Juergen Gross
2021-01-20 13:55 ` [PATCH v4 14/15] x86/paravirt: switch functions with custom code to ALTERNATIVE Juergen Gross
2021-01-20 13:55 ` [PATCH v4 15/15] x86/paravirt: have only one paravirt patch function Juergen Gross
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