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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v3 4/4] x86/ucode: Add Kconfig option to remove microcode loading
Amend docs to reflect ucode= command/stanza depend on MICROCODE_LOADING
being set.
The new MICROCODE_OP() is a conditional setter for the microcode_ops
struct. By using IS_ENABLED() there ratehr than ifdef we allow DCE to
remove all statics no longer used when microcode loading is disabled
without tagging them with __maybe_unused.
Signed-off-by: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
---
v3:
* Moved MICROCODE_SCAN_DEFAULT to a separate patch
* Added doc change to admin-guide
* Added Andrew's suggestion for Kconfig help text
* Inlined can_apply_microcode() macro in core.c
* Kept the platform-ops, gating them on CONFIG_MICROCODE_LOADING
through the new MICROCODE_OP() macro.
---
docs/admin-guide/microcode-loading.rst | 2 ++
docs/misc/efi.pandoc | 2 ++
docs/misc/xen-command-line.pandoc | 2 +-
xen/arch/x86/Kconfig | 14 ++++++++++++++
xen/arch/x86/cpu/microcode/amd.c | 16 +++++++++-------
xen/arch/x86/cpu/microcode/core.c | 15 ++++++++++++---
xen/arch/x86/cpu/microcode/intel.c | 11 +++++++----
xen/arch/x86/cpu/microcode/private.h | 2 ++
xen/arch/x86/efi/efi-boot.h | 3 ++-
xen/arch/x86/platform_hypercall.c | 22 +++++++++++++++-------
10 files changed, 66 insertions(+), 23 deletions(-)
diff --git a/docs/admin-guide/microcode-loading.rst
b/docs/admin-guide/microcode-loading.rst
index a07e25802f..148bc8559b 100644
--- a/docs/admin-guide/microcode-loading.rst
+++ b/docs/admin-guide/microcode-loading.rst
@@ -23,6 +23,8 @@ TSX errata which necessitated disabling the feature
entirely), or the addition
of brand new features (e.g. the Spectre v2 controls to work around speculative
execution vulnerabilities).
+Microcode loading support in Xen is controlled by the
+``CONFIG_MICROCODE_LOADING`` Kconfig option.
Boot time microcode loading
---------------------------
diff --git a/docs/misc/efi.pandoc b/docs/misc/efi.pandoc
index 11c1ac3346..c3fb1f3a30 100644
--- a/docs/misc/efi.pandoc
+++ b/docs/misc/efi.pandoc
@@ -104,6 +104,8 @@ Specifies an XSM module to load.
Specifies a CPU microcode blob to load. (x86 only)
+Only available when Xen is compiled with CONFIG_MICROCODE_LOADING.
+
###`dtb=<filename>`
Specifies a device tree file to load. The platform firmware may provide a
diff --git a/docs/misc/xen-command-line.pandoc
b/docs/misc/xen-command-line.pandoc
index 15f7a315a4..866fa2f951 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -2748,7 +2748,7 @@ performance.
### ucode
> `= List of [ <integer> | scan=<bool>, nmi=<bool>, digest-check=<bool> ]`
- Applicability: x86
+ Applicability: x86 with CONFIG_MICROCODE_LOADING active
Default: `scan` is selectable via Kconfig, `nmi,digest-check`
Controls for CPU microcode loading. For early loading, this parameter can
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index d5705e4bff..61f58aa829 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -331,8 +331,22 @@ config REQUIRE_NX
was unavailable. However, if enabled, Xen will no longer boot on
any CPU which is lacking NX support.
+config MICROCODE_LOADING
+ bool "Microcode loading"
+ default y
+ help
+ Microcode updates for CPUs fix errata and provide new functionality
for
+ software to work around bugs, such as the speculative execution
+ vulnerabilities. It is common for OSes to carry updated microcode as
+ software tends to get updated more frequently than firmware.
+
+ For embedded environments where a full firmware/software stack is
being
+ provided, it might not be necessary for Xen to need to load microcode
+ itself.
+
config MICROCODE_SCAN_DEFAULT
bool "Scan for microcode by default"
+ depends on MICROCODE_LOADING
help
During boot, Xen can scan the multiboot images for a CPIO archive
containing CPU microcode to be loaded, which is Linux's mechanism for
diff --git a/xen/arch/x86/cpu/microcode/amd.c b/xen/arch/x86/cpu/microcode/amd.c
index 71b041c84b..86706a21a6 100644
--- a/xen/arch/x86/cpu/microcode/amd.c
+++ b/xen/arch/x86/cpu/microcode/amd.c
@@ -561,11 +561,11 @@ static const char __initconst amd_cpio_path[] =
"kernel/x86/microcode/AuthenticAMD.bin";
static const struct microcode_ops __initconst_cf_clobber amd_ucode_ops = {
- .cpu_request_microcode = cpu_request_microcode,
+ .cpu_request_microcode = MICROCODE_OP(cpu_request_microcode),
.collect_cpu_info = collect_cpu_info,
- .apply_microcode = apply_microcode,
- .compare = amd_compare,
- .cpio_path = amd_cpio_path,
+ .apply_microcode = MICROCODE_OP(apply_microcode),
+ .compare = MICROCODE_OP(amd_compare),
+ .cpio_path = MICROCODE_OP(amd_cpio_path),
};
void __init ucode_probe_amd(struct microcode_ops *ops)
@@ -574,7 +574,8 @@ void __init ucode_probe_amd(struct microcode_ops *ops)
* The Entrysign vulnerability (SB-7033, CVE-2024-36347) affects Zen1-5
* CPUs. Taint Xen if digest checking is turned off.
*/
- if ( boot_cpu_data.family >= 0x17 && boot_cpu_data.family <= 0x1a &&
+ if ( IS_ENABLED(CONFIG_MICROCODE_LOADING) &&
+ boot_cpu_data.family >= 0x17 && boot_cpu_data.family <= 0x1a &&
!opt_digest_check )
{
printk(XENLOG_WARNING
@@ -614,8 +615,9 @@ void __init amd_check_entrysign(void)
unsigned int curr_rev;
uint8_t fixed_rev;
- if ( boot_cpu_data.vendor != X86_VENDOR_AMD ||
- boot_cpu_data.family < 0x17 ||
+ if ( !IS_ENABLED(CONFIG_MICROCODE_LOADING) ||
+ boot_cpu_data.vendor != X86_VENDOR_AMD ||
+ boot_cpu_data.family < 0x17 ||
boot_cpu_data.family > 0x1a )
return;
diff --git a/xen/arch/x86/cpu/microcode/core.c
b/xen/arch/x86/cpu/microcode/core.c
index dabdb95b4c..efaf808f1a 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -58,7 +58,7 @@
*/
#define MICROCODE_UPDATE_TIMEOUT_US 1000000
-static bool __initdata ucode_mod_forced;
+static bool __initdata __maybe_unused ucode_mod_forced;
static unsigned int nr_cores;
/*
@@ -104,6 +104,7 @@ static int __initdata opt_mod_idx;
static bool __initdata opt_scan = IS_ENABLED(CONFIG_MICROCODE_SCAN_DEFAULT);
bool __ro_after_init opt_digest_check = true;
+#ifdef CONFIG_MICROCODE_LOADING
/*
* Used by the EFI path only, when xen.cfg identifies an explicit microcode
* file. Overrides ucode=<int>|scan on the regular command line.
@@ -162,6 +163,7 @@ static int __init cf_check parse_ucode(const char *s)
return rc;
}
custom_param("ucode", parse_ucode);
+#endif /* CONFIG_MICROCODE_LOADING */
static struct microcode_ops __ro_after_init ucode_ops;
@@ -469,7 +471,7 @@ struct ucode_buf {
char buffer[];
};
-static long cf_check ucode_update_hcall_cont(void *data)
+static long cf_check __maybe_unused ucode_update_hcall_cont(void *data)
{
struct microcode_patch *patch = NULL;
int ret, result;
@@ -613,6 +615,7 @@ static long cf_check ucode_update_hcall_cont(void *data)
return ret;
}
+#ifdef CONFIG_MICROCODE_LOADING
int ucode_update_hcall(XEN_GUEST_HANDLE(const_void) buf,
unsigned long len, unsigned int flags)
{
@@ -645,6 +648,7 @@ int ucode_update_hcall(XEN_GUEST_HANDLE(const_void) buf,
*/
return continue_hypercall_on_cpu(0, ucode_update_hcall_cont, buffer);
}
+#endif /* CONFIG_MICROCODE_LOADING */
/* Load a cached update to current cpu */
int microcode_update_one(void)
@@ -658,7 +662,7 @@ int microcode_update_one(void)
if ( ucode_ops.collect_cpu_info )
alternative_vcall(ucode_ops.collect_cpu_info);
- if ( !ucode_ops.apply_microcode )
+ if ( !IS_ENABLED(CONFIG_MICROCODE_LOADING) || !ucode_ops.apply_microcode )
return -EOPNOTSUPP;
spin_lock(µcode_mutex);
@@ -678,6 +682,7 @@ int microcode_update_one(void)
*/
static int __initdata early_mod_idx = -1;
+#ifdef CONFIG_MICROCODE_LOADING
static int __init cf_check microcode_init_cache(void)
{
struct boot_info *bi = &xen_boot_info;
@@ -734,6 +739,7 @@ static int __init cf_check microcode_init_cache(void)
return rc;
}
presmp_initcall(microcode_init_cache);
+#endif /* CONFIG_MICROCODE_LOADING */
/*
* There are several tasks:
@@ -898,6 +904,9 @@ int __init early_microcode_init(struct boot_info *bi)
printk(XENLOG_INFO "BSP microcode revision: 0x%08x\n",
this_cpu(cpu_sig).rev);
+ if ( !IS_ENABLED(CONFIG_MICROCODE_LOADING) )
+ return -ENODEV;
+
/*
* Some hypervisors deliberately report a microcode revision of -1 to
* mean that they will not accept microcode updates.
diff --git a/xen/arch/x86/cpu/microcode/intel.c
b/xen/arch/x86/cpu/microcode/intel.c
index 281993e725..ba99f4ffdc 100644
--- a/xen/arch/x86/cpu/microcode/intel.c
+++ b/xen/arch/x86/cpu/microcode/intel.c
@@ -408,17 +408,20 @@ static const char __initconst intel_cpio_path[] =
"kernel/x86/microcode/GenuineIntel.bin";
static const struct microcode_ops __initconst_cf_clobber intel_ucode_ops = {
- .cpu_request_microcode = cpu_request_microcode,
+ .cpu_request_microcode = MICROCODE_OP(cpu_request_microcode),
.collect_cpu_info = collect_cpu_info,
- .apply_microcode = apply_microcode,
- .compare = intel_compare,
- .cpio_path = intel_cpio_path,
+ .apply_microcode = MICROCODE_OP(apply_microcode),
+ .compare = MICROCODE_OP(intel_compare),
+ .cpio_path = MICROCODE_OP(intel_cpio_path),
};
void __init ucode_probe_intel(struct microcode_ops *ops)
{
*ops = intel_ucode_ops;
+ if ( !IS_ENABLED(CONFIG_MICROCODE_LOADING) )
+ return;
+
if ( !can_load_microcode() )
ops->apply_microcode = NULL;
}
diff --git a/xen/arch/x86/cpu/microcode/private.h
b/xen/arch/x86/cpu/microcode/private.h
index e6c965dc99..1167b79db1 100644
--- a/xen/arch/x86/cpu/microcode/private.h
+++ b/xen/arch/x86/cpu/microcode/private.h
@@ -93,4 +93,6 @@ void ucode_probe_intel(struct microcode_ops *ops);
static inline void ucode_probe_intel(struct microcode_ops *ops) {}
#endif
+#define MICROCODE_OP(x) (IS_ENABLED(CONFIG_MICROCODE_LOADING) ? (x) : NULL)
+
#endif /* ASM_X86_MICROCODE_PRIVATE_H */
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index 0194720003..42a2c46b5e 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -295,7 +295,8 @@ static void __init efi_arch_cfg_file_late(const
EFI_LOADED_IMAGE *image,
{
union string name;
- if ( read_section(image, L"ucode", &ucode, NULL) )
+ if ( !IS_ENABLED(CONFIG_MICROCODE_LOADING) ||
+ read_section(image, L"ucode", &ucode, NULL) )
return;
name.s = get_value(&cfg, section, "ucode");
diff --git a/xen/arch/x86/platform_hypercall.c
b/xen/arch/x86/platform_hypercall.c
index 79bb99e0b6..a55060e662 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -309,22 +309,30 @@ ret_t do_platform_op(
case XENPF_microcode_update:
{
- XEN_GUEST_HANDLE(const_void) data;
+ ret = -EOPNOTSUPP;
+ if ( IS_ENABLED(CONFIG_MICROCODE_LOADING) )
+ {
+ XEN_GUEST_HANDLE(const_void) data;
- guest_from_compat_handle(data, op->u.microcode.data);
+ guest_from_compat_handle(data, op->u.microcode.data);
+ ret = ucode_update_hcall(data, op->u.microcode.length, 0);
+ }
- ret = ucode_update_hcall(data, op->u.microcode.length, 0);
break;
}
case XENPF_microcode_update2:
{
- XEN_GUEST_HANDLE(const_void) data;
+ ret = -EOPNOTSUPP;
+ if ( IS_ENABLED(CONFIG_MICROCODE_LOADING) )
+ {
+ XEN_GUEST_HANDLE(const_void) data;
- guest_from_compat_handle(data, op->u.microcode2.data);
+ guest_from_compat_handle(data, op->u.microcode2.data);
+ ret = ucode_update_hcall(data, op->u.microcode2.length,
+ op->u.microcode2.flags);
+ }
- ret = ucode_update_hcall(data, op->u.microcode2.length,
- op->u.microcode2.flags);
break;
}
--
2.43.0
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