From: Juergen Gross <jgross@suse.com>
To: xen-devel@lists.xenproject.org, x86@kernel.org,
linux-kernel@vger.kernel.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>
Subject: [PATCH v3 08/15] x86: add new features for paravirt patching
Date: Thu, 17 Dec 2020 10:31:26 +0100 [thread overview]
Message-ID: <20201217093133.1507-9-jgross@suse.com> (raw)
In-Reply-To: <20201217093133.1507-1-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)
---
arch/x86/include/asm/cpufeatures.h | 2 ++
arch/x86/kernel/alternative.c | 40 ++++++++++++++++++++++++++++--
2 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index f5ef2d5b9231..1077b675a008 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -237,6 +237,8 @@
#define X86_FEATURE_VMCALL ( 8*32+18) /* "" Hypervisor supports the VMCALL instruction */
#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_PVUNLOCK ( 8*32+21) /* "" PV unlock function */
+#define X86_FEATURE_VCPUPREEMPT ( 8*32+22) /* "" 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/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 0a904fb2678b..abb481808811 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -600,6 +600,15 @@ int alternatives_text_reserved(void *start, void *end)
#endif /* CONFIG_SMP */
#ifdef CONFIG_PARAVIRT
+static 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);
+}
+
void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
struct paravirt_patch_site *end)
{
@@ -623,6 +632,8 @@ void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
}
extern struct paravirt_patch_site __start_parainstructions[],
__stop_parainstructions[];
+#else
+static void __init paravirt_set_cap(void) { }
#endif /* CONFIG_PARAVIRT */
/*
@@ -730,6 +741,33 @@ 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 +786,6 @@ void __init alternative_instructions(void)
}
#endif
- apply_paravirt(__parainstructions, __parainstructions_end);
-
restart_nmi();
alternatives_patched = 1;
}
--
2.26.2
next prev parent reply other threads:[~2020-12-17 9:32 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 9:31 [PATCH v3 00/15] x86: major paravirt cleanup Juergen Gross
2020-12-17 9:31 ` [PATCH v3 01/15] x86/xen: use specific Xen pv interrupt entry for MCE Juergen Gross
2020-12-17 9:31 ` [PATCH v3 02/15] x86/xen: use specific Xen pv interrupt entry for DF Juergen Gross
2020-12-17 9:31 ` [PATCH v3 03/15] x86/pv: switch SWAPGS to ALTERNATIVE Juergen Gross
2020-12-17 9:31 ` [PATCH v3 04/15] x86/xen: drop USERGS_SYSRET64 paravirt call Juergen Gross
2020-12-17 9:31 ` [PATCH v3 05/15] x86: rework arch_local_irq_restore() to not use popf Juergen Gross
2020-12-17 9:31 ` [PATCH v3 06/15] x86/paravirt: switch time pvops functions to use static_call() Juergen Gross
2020-12-17 17:31 ` Michael Kelley
2021-01-06 10:41 ` Borislav Petkov
2021-01-19 11:36 ` Jürgen Groß
2021-01-06 10:03 ` Borislav Petkov
2021-01-19 11:33 ` Jürgen Groß
2020-12-17 9:31 ` [PATCH v3 07/15] x86/alternative: support "not feature" and ALTERNATIVE_TERNARY Juergen Gross
2021-01-07 19:08 ` Borislav Petkov
2021-01-19 11:35 ` Jürgen Groß
2021-01-19 12:06 ` Borislav Petkov
2021-01-19 12:12 ` Jürgen Groß
2020-12-17 9:31 ` Juergen Gross [this message]
2020-12-17 13:12 ` [PATCH v3 08/15] x86: add new features for paravirt patching kernel test robot
2021-01-14 18:30 ` Borislav Petkov
2021-01-14 18:40 ` Borislav Petkov
2020-12-17 9:31 ` [PATCH v3 09/15] x86/paravirt: remove no longer needed 32-bit pvops cruft Juergen Gross
2020-12-17 9:31 ` [PATCH v3 10/15] x86/paravirt: simplify paravirt macros Juergen Gross
2020-12-17 16:46 ` kernel test robot
2020-12-17 9:31 ` [PATCH v3 11/15] x86/paravirt: switch iret pvops to ALTERNATIVE Juergen Gross
2020-12-17 9:31 ` [PATCH v3 12/15] objtool: Alternatives vs ORC, the hard way Juergen Gross
2020-12-17 9:31 ` [PATCH v3 13/15] x86/paravirt: add new macros PVOP_ALT* supporting pvops in ALTERNATIVEs Juergen Gross
2020-12-17 9:31 ` [PATCH v3 14/15] x86/paravirt: switch functions with custom code to ALTERNATIVE Juergen Gross
2020-12-17 16:42 ` kernel test robot
2020-12-17 9:31 ` [PATCH v3 15/15] x86/paravirt: have only one paravirt patch function Juergen Gross
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