2020-04-14 15:42:38

by Mihai Carabas

[permalink] [raw]
Subject: [PATCH] x86: microcode: fix return value for microcode late loading

The return value from stop_machine might not be consistent.

stop_machine_cpuslocked returns:
- zero if all functions have returned 0
- a non-zero value if at least one of the functions returned
a non-zero value

There is no way to know if it is negative or positive. So make
__reload_late return 0 on success, or negative otherwise.

Signed-off-by: Mihai Carabas <[email protected]>
---
arch/x86/kernel/cpu/microcode/core.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 7019d4b..336003e 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -545,8 +545,7 @@ static int __wait_for_cpus(atomic_t *t, long long timeout)
/*
* Returns:
* < 0 - on error
- * 0 - no update done
- * 1 - microcode was updated
+ * 0 - success (no update done or microcode was updated)
*/
static int __reload_late(void *info)
{
@@ -573,11 +572,9 @@ static int __reload_late(void *info)
else
goto wait_for_siblings;

- if (err > UCODE_NFOUND) {
+ if (err >= UCODE_NFOUND) {
pr_warn("Error reloading microcode on CPU %d\n", cpu);
ret = -1;
- } else if (err == UCODE_UPDATED || err == UCODE_OK) {
- ret = 1;
}

wait_for_siblings:
@@ -608,7 +605,7 @@ static int microcode_reload_late(void)
atomic_set(&late_cpus_out, 0);

ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
- if (ret > 0)
+ if (ret == 0)
microcode_check();

pr_info("Reload completed, microcode revision: 0x%x\n", boot_cpu_data.microcode);
@@ -649,7 +646,7 @@ static ssize_t reload_store(struct device *dev,
put:
put_online_cpus();

- if (ret >= 0)
+ if (ret == 0)
ret = size;

return ret;
--
1.8.3.1


2020-04-15 21:45:47

by Peter Zijlstra

[permalink] [raw]
Subject: Re: [PATCH] x86: microcode: fix return value for microcode late loading

On Tue, Apr 14, 2020 at 12:55:35PM +0300, Mihai Carabas wrote:
> The return value from stop_machine might not be consistent.
>
> stop_machine_cpuslocked returns:
> - zero if all functions have returned 0
> - a non-zero value if at least one of the functions returned
> a non-zero value
>
> There is no way to know if it is negative or positive. So make
> __reload_late return 0 on success, or negative otherwise.
>
> Signed-off-by: Mihai Carabas <[email protected]>

Isn't the right fix to disable late-loading?

2020-04-17 15:11:51

by Borislav Petkov

[permalink] [raw]
Subject: Re: [PATCH] x86: microcode: fix return value for microcode late loading

On Tue, Apr 14, 2020 at 12:55:35PM +0300, Mihai Carabas wrote:
> The return value from stop_machine might not be consistent.
>
> stop_machine_cpuslocked returns:
> - zero if all functions have returned 0
> - a non-zero value if at least one of the functions returned
> a non-zero value
>
> There is no way to know if it is negative or positive. So make
> __reload_late return 0 on success, or negative otherwise.
>
> Signed-off-by: Mihai Carabas <[email protected]>
> ---
> arch/x86/kernel/cpu/microcode/core.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
> index 7019d4b..336003e 100644
> --- a/arch/x86/kernel/cpu/microcode/core.c
> +++ b/arch/x86/kernel/cpu/microcode/core.c
> @@ -545,8 +545,7 @@ static int __wait_for_cpus(atomic_t *t, long long timeout)
> /*
> * Returns:
> * < 0 - on error
> - * 0 - no update done
> - * 1 - microcode was updated
> + * 0 - success (no update done or microcode was updated)
> */
> static int __reload_late(void *info)
> {
> @@ -573,11 +572,9 @@ static int __reload_late(void *info)
> else
> goto wait_for_siblings;
>
> - if (err > UCODE_NFOUND) {
> + if (err >= UCODE_NFOUND) {

It is not an error if no microcode was found.

> pr_warn("Error reloading microcode on CPU %d\n", cpu);
^^^^^^^^^^

> ret = -1;

--
Regards/Gruss,
Boris.

https://people.kernel.org/tglx/notes-about-netiquette

2020-04-21 20:12:28

by Mihai Carabas

[permalink] [raw]
Subject: [PATCH v2] x86: microcode: fix return value for microcode late loading

The return value from stop_machine might not be consistent.

stop_machine_cpuslocked returns:
- zero if all functions have returned 0
- a non-zero value if at least one of the functions returned
a non-zero value

There is no way to know if it is negative or positive. So make
__reload_late return 0 on success, or negative otherwise.

Signed-off-by: Mihai Carabas <[email protected]>
---
Changes in v2:
- do not print anything on UCODE_NFOUND as microcode not found
is not an error

arch/x86/kernel/cpu/microcode/core.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 7019d4b..a2ae3da 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -545,8 +545,7 @@ static int __wait_for_cpus(atomic_t *t, long long timeout)
/*
* Returns:
* < 0 - on error
- * 0 - no update done
- * 1 - microcode was updated
+ * 0 - success (no update done or microcode was updated)
*/
static int __reload_late(void *info)
{
@@ -576,8 +575,8 @@ static int __reload_late(void *info)
if (err > UCODE_NFOUND) {
pr_warn("Error reloading microcode on CPU %d\n", cpu);
ret = -1;
- } else if (err == UCODE_UPDATED || err == UCODE_OK) {
- ret = 1;
+ } else if (err == UCODE_NFOUND) {
+ ret = -1;
}

wait_for_siblings:
@@ -608,7 +607,7 @@ static int microcode_reload_late(void)
atomic_set(&late_cpus_out, 0);

ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
- if (ret > 0)
+ if (ret == 0)
microcode_check();

pr_info("Reload completed, microcode revision: 0x%x\n", boot_cpu_data.microcode);
@@ -649,7 +648,7 @@ static ssize_t reload_store(struct device *dev,
put:
put_online_cpus();

- if (ret >= 0)
+ if (ret == 0)
ret = size;

return ret;
--
1.8.3.1

2020-04-22 18:05:48

by tip-bot2 for Haifeng Xu

[permalink] [raw]
Subject: [tip: x86/microcode] x86/microcode: Fix return value for microcode late loading

The following commit has been merged into the x86/microcode branch of tip:

Commit-ID: 9adbf3c609af92a57a73000a3cb8f4c2d307dfa3
Gitweb: https://git.kernel.org/tip/9adbf3c609af92a57a73000a3cb8f4c2d307dfa3
Author: Mihai Carabas <[email protected]>
AuthorDate: Tue, 21 Apr 2020 22:28:38 +03:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Wed, 22 Apr 2020 19:55:50 +02:00

x86/microcode: Fix return value for microcode late loading

The return value from stop_machine() might not be consistent.

stop_machine_cpuslocked() returns:
- zero if all functions have returned 0.
- a non-zero value if at least one of the functions returned
a non-zero value.

There is no way to know if it is negative or positive. So make
__reload_late() return 0 on success or negative otherwise.

[ bp: Unify ret val check and touch up. ]

Signed-off-by: Mihai Carabas <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/kernel/cpu/microcode/core.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 7019d4b..baec68b 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -545,8 +545,7 @@ static int __wait_for_cpus(atomic_t *t, long long timeout)
/*
* Returns:
* < 0 - on error
- * 0 - no update done
- * 1 - microcode was updated
+ * 0 - success (no update done or microcode was updated)
*/
static int __reload_late(void *info)
{
@@ -573,11 +572,11 @@ static int __reload_late(void *info)
else
goto wait_for_siblings;

- if (err > UCODE_NFOUND) {
- pr_warn("Error reloading microcode on CPU %d\n", cpu);
+ if (err >= UCODE_NFOUND) {
+ if (err == UCODE_ERROR)
+ pr_warn("Error reloading microcode on CPU %d\n", cpu);
+
ret = -1;
- } else if (err == UCODE_UPDATED || err == UCODE_OK) {
- ret = 1;
}

wait_for_siblings:
@@ -608,7 +607,7 @@ static int microcode_reload_late(void)
atomic_set(&late_cpus_out, 0);

ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
- if (ret > 0)
+ if (ret == 0)
microcode_check();

pr_info("Reload completed, microcode revision: 0x%x\n", boot_cpu_data.microcode);
@@ -649,7 +648,7 @@ static ssize_t reload_store(struct device *dev,
put:
put_online_cpus();

- if (ret >= 0)
+ if (ret == 0)
ret = size;

return ret;