Logic in early_acpi_process_madt() & acpi_process_madt() is really hard to
follow now. Clean them up.
Done basic boot test on my x86-64 PC.
CCed [email protected]
Cao jin (2):
x86/acpi: Improve code readablity of early madt processing
x86/acpi: Cleanup acpi_process_madt()
arch/x86/kernel/acpi/boot.c | 72 +++++++++++++++----------------------
1 file changed, 28 insertions(+), 44 deletions(-)
--
2.21.0
Current processing logic is confusing.
Return value of early_acpi_parse_madt_lapic_addr_ovr() indicates error(< 0),
parsed entry number(>= 0). So, it makes no sense to initialize acpi_lapic &
smp_found_config seeing no override entry, instead, initialize them seeing
MADT.
Put register_lapic_address() into override entry processing doesn't make
sense either.
Improved all the related comments too.
Signed-off-by: Cao jin <[email protected]>
---
arch/x86/kernel/acpi/boot.c | 28 ++++++++++------------------
1 file changed, 10 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 04205ce127a1..2131035bba98 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1003,11 +1003,7 @@ static int __init acpi_parse_fadt(struct acpi_table_header *table)
}
#ifdef CONFIG_X86_LOCAL_APIC
-/*
- * Parse LAPIC entries in MADT
- * returns 0 on success, < 0 on error
- */
-
+/* Returns >= 0 on success, indicates parsed entry number; < 0 on error. */
static int __init early_acpi_parse_madt_lapic_addr_ovr(void)
{
int count;
@@ -1025,11 +1021,8 @@ static int __init early_acpi_parse_madt_lapic_addr_ovr(void)
if (count < 0) {
printk(KERN_ERR PREFIX
"Error parsing LAPIC address override entry\n");
- return count;
}
- register_lapic_address(acpi_lapic_addr);
-
return count;
}
@@ -1234,19 +1227,16 @@ static inline int acpi_parse_madt_ioapic_entries(void)
static void __init early_acpi_process_madt(void)
{
#ifdef CONFIG_X86_LOCAL_APIC
- int error;
+ int ret;
if (!acpi_table_parse(ACPI_SIG_MADT, acpi_parse_madt)) {
+ /* Found MADT */
+ acpi_lapic = 1;
+ smp_found_config = 1;
- /*
- * Parse MADT LAPIC entries
- */
- error = early_acpi_parse_madt_lapic_addr_ovr();
- if (!error) {
- acpi_lapic = 1;
- smp_found_config = 1;
- }
- if (error == -EINVAL) {
+ /* See if override entry exists. */
+ ret = early_acpi_parse_madt_lapic_addr_ovr();
+ if (ret == -EINVAL) {
/*
* Dell Precision Workstation 410, 610 come here.
*/
@@ -1254,6 +1244,8 @@ static void __init early_acpi_process_madt(void)
"Invalid BIOS MADT, disabling ACPI\n");
disable_acpi();
}
+
+ register_lapic_address(acpi_lapic_addr);
}
#endif
}
--
2.21.0
After many duct-taped patches, the readablity of these code chunks are
really hard. This patch does following improvements:
1. Drop unnecessary comment that is self-documented by function name,
while supply with necessary comments.
2. Drop duplicated code: acpi_process_madt() has already been called
in early madt processing, acpi_lapic & smp_found_config is also
initialized there.
3. Fix code logic: variable count's usage is quite confusing now, and
some code logic is wrong, like count & x2count will never be negative
after assigned from madt_proc[n].count
Signed-off-by: Cao jin <[email protected]>
---
arch/x86/kernel/acpi/boot.c | 44 +++++++++++++++----------------------
1 file changed, 18 insertions(+), 26 deletions(-)
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 2131035bba98..844fc9f26064 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1026,9 +1026,10 @@ static int __init early_acpi_parse_madt_lapic_addr_ovr(void)
return count;
}
+/* Returns 0 on success, < 0 on error. */
static int __init acpi_parse_madt_lapic_entries(void)
{
- int count;
+ int count = 0;
int x2count = 0;
int ret;
struct acpi_subtable_proc madt_proc[2];
@@ -1036,10 +1037,13 @@ static int __init acpi_parse_madt_lapic_entries(void)
if (!boot_cpu_has(X86_FEATURE_APIC))
return -ENODEV;
- count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_SAPIC,
- acpi_parse_sapic, MAX_LOCAL_APIC);
+ /* SAPIC is commonly found on Intel Itanium processor. */
+ ret = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_SAPIC,
+ acpi_parse_sapic, MAX_LOCAL_APIC);
- if (!count) {
+
+ /* No SAPIC entries implies it is not Itanium processor. */
+ if (!ret) {
memset(madt_proc, 0, sizeof(madt_proc));
madt_proc[0].id = ACPI_MADT_TYPE_LOCAL_APIC;
madt_proc[0].handler = acpi_parse_lapic;
@@ -1056,15 +1060,14 @@ static int __init acpi_parse_madt_lapic_entries(void)
count = madt_proc[0].count;
x2count = madt_proc[1].count;
- }
- if (!count && !x2count) {
- printk(KERN_ERR PREFIX "No LAPIC entries present\n");
- /* TBD: Cleanup to allow fallback to MPS */
- return -ENODEV;
- } else if (count < 0 || x2count < 0) {
- printk(KERN_ERR PREFIX "Error parsing LAPIC entry\n");
- /* TBD: Cleanup to allow fallback to MPS */
- return count;
+ if (!count && !x2count) {
+ printk(KERN_ERR PREFIX "No LAPIC entries present\n");
+ /* TBD: Cleanup to allow fallback to MPS */
+ return -ENODEV;
+ }
+ } else if (ret < 0) {
+ printk(KERN_ERR PREFIX "Error parsing SAPIC entries\n");
+ return ret;
}
x2count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_X2APIC_NMI,
@@ -1074,7 +1077,7 @@ static int __init acpi_parse_madt_lapic_entries(void)
if (count < 0 || x2count < 0) {
printk(KERN_ERR PREFIX "Error parsing LAPIC NMI entry\n");
/* TBD: Cleanup to allow fallback to MPS */
- return count;
+ return (count < 0) ? count : x2count;
}
return 0;
}
@@ -1255,25 +1258,14 @@ static void __init acpi_process_madt(void)
#ifdef CONFIG_X86_LOCAL_APIC
int error;
- if (!acpi_table_parse(ACPI_SIG_MADT, acpi_parse_madt)) {
-
- /*
- * Parse MADT LAPIC entries
- */
+ if (acpi_lapic) {
error = acpi_parse_madt_lapic_entries();
if (!error) {
- acpi_lapic = 1;
-
- /*
- * Parse MADT IO-APIC entries
- */
mutex_lock(&acpi_ioapic_lock);
error = acpi_parse_madt_ioapic_entries();
mutex_unlock(&acpi_ioapic_lock);
if (!error) {
acpi_set_irq_model_ioapic();
-
- smp_found_config = 1;
}
}
if (error == -EINVAL) {
--
2.21.0
Ping.
On 1/23/20 9:41 AM, Cao jin wrote:
> Logic in early_acpi_process_madt() & acpi_process_madt() is really hard to
> follow now. Clean them up.
>
> Done basic boot test on my x86-64 PC.
>
> CCed [email protected]
>
> Cao jin (2):
> x86/acpi: Improve code readablity of early madt processing
> x86/acpi: Cleanup acpi_process_madt()
>
> arch/x86/kernel/acpi/boot.c | 72 +++++++++++++++----------------------
> 1 file changed, 28 insertions(+), 44 deletions(-)
>
--
Sincerely,
Cao jin
On Thu, Jan 23, 2020 at 09:41:43AM +0800, Cao jin wrote:
> Current processing logic is confusing.
>
> Return value of early_acpi_parse_madt_lapic_addr_ovr() indicates error(< 0),
> parsed entry number(>= 0).
You mean, the count of table entries parsed successfully?
> So, it makes no sense to initialize acpi_lapic & smp_found_config
> seeing no override entry, instead, initialize them seeing MADT.
Err, that logical conclusion is not really clear to me - pls try
again with more detail. I kinda see what you mean by looking at
acpi_process_madt() but before I commit a change like that, I better
have the warm and fuzzy feeling that it is correct and properly
explained in its commit message.
So why did
cbf9bd603ab1 ("acpi: get boot_cpu_id as early for k8_scan_nodes")
do it this way? Was it wrong or why?
I'm very wary about touching ACPI parsing code for no good reason
because, well, it is ACPI...
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On 2/24/20 9:21 PM, Borislav Petkov wrote:
> On Thu, Jan 23, 2020 at 09:41:43AM +0800, Cao jin wrote:
>> Current processing logic is confusing.
>>
>> Return value of early_acpi_parse_madt_lapic_addr_ovr() indicates error(< 0),
>> parsed entry number(>= 0).
>
> You mean, the count of table entries parsed successfully?
Yes, 0 for no override sub-table.
>
>> So, it makes no sense to initialize acpi_lapic & smp_found_config
>> seeing no override entry, instead, initialize them seeing MADT.
>
> Err, that logical conclusion is not really clear to me - pls try
> again with more detail. I kinda see what you mean by looking at
> acpi_process_madt() but before I commit a change like that, I better
> have the warm and fuzzy feeling that it is correct and properly
> explained in its commit message.
>
My understanding of early_acpi_process_madt(): mainly for getting APIC
register base address(acpi_lapic_addr) from MADT, then process it via
register_lapic_address(). acpi_lapic_addr could be got from one of
following 2 places:
1. MADT header (32-bit address, always exist)
2. MADT sub-table: Local APIC Address Override (64-bit address,
optional, high priority and use it if present)
So the making-sense logic to me goes like:
1. get (32-bit) acpi_lapic_addr from MADT header.
2. check if there is MADT override structure & get 64-bit
acpi_lapic_addr if present.
3. register_lapic_address(acpi_lapic_addr);
Then, it looks weird to me putting register_lapic_address() into
early_acpi_parse_madt_lapic_addr_ovr(), the result is not wrong, but the
code logic is hard for newbie. (these 2 functions both does more than
its name tells, register_lapic_address() also get boot cpu APIC ID &
version.)
Variable acpi_lapic and its counterpart smp_found_config from MPS
indicate whether it is SMP system, right? The following code:
error = early_acpi_parse_madt_lapic_addr_ovr();
if (!error) {
acpi_lapic = 1;
smp_found_config = 1;
}
means setting them when there is no override sub-table, so why can't
moving the setting operation out? Another issue: if there *is* override
sub-table, don't set those two?
> So why did
>
> cbf9bd603ab1 ("acpi: get boot_cpu_id as early for k8_scan_nodes")
>
> do it this way? Was it wrong or why?
Not a clue... The title says it wants boot_cpu_physical_apicid, but did
many other things. Maybe Thomas could provide some insights?
>
> I'm very wary about touching ACPI parsing code for no good reason
> because, well, it is ACPI...
I was expecting ACPI guys could help to confirm;) I also understand this
should be tested widely, but I just have a normal PC, so it is a RFC:)
--
Sincerely,
Cao jin
Hello BP,
Does the explanation make sense to you?
BTW, also test it on i386, boots fine.
--
Sincerely,
Cao jin
On 2/25/20 3:02 PM, Cao jin wrote:
> On 2/24/20 9:21 PM, Borislav Petkov wrote:
>> On Thu, Jan 23, 2020 at 09:41:43AM +0800, Cao jin wrote:
>>> Current processing logic is confusing.
>>>
>>> Return value of early_acpi_parse_madt_lapic_addr_ovr() indicates error(< 0),
>>> parsed entry number(>= 0).
>>
>> You mean, the count of table entries parsed successfully?
>
> Yes, 0 for no override sub-table.
>
>>
>>> So, it makes no sense to initialize acpi_lapic & smp_found_config
>>> seeing no override entry, instead, initialize them seeing MADT.
>>
>> Err, that logical conclusion is not really clear to me - pls try
>> again with more detail. I kinda see what you mean by looking at
>> acpi_process_madt() but before I commit a change like that, I better
>> have the warm and fuzzy feeling that it is correct and properly
>> explained in its commit message.
>>
>
> My understanding of early_acpi_process_madt(): mainly for getting APIC
> register base address(acpi_lapic_addr) from MADT, then process it via
> register_lapic_address(). acpi_lapic_addr could be got from one of
> following 2 places:
>
> 1. MADT header (32-bit address, always exist)
> 2. MADT sub-table: Local APIC Address Override (64-bit address,
> optional, high priority and use it if present)
>
> So the making-sense logic to me goes like:
>
> 1. get (32-bit) acpi_lapic_addr from MADT header.
> 2. check if there is MADT override structure & get 64-bit
> acpi_lapic_addr if present.
> 3. register_lapic_address(acpi_lapic_addr);
>
> Then, it looks weird to me putting register_lapic_address() into
> early_acpi_parse_madt_lapic_addr_ovr(), the result is not wrong, but the
> code logic is hard for newbie. (these 2 functions both does more than
> its name tells, register_lapic_address() also get boot cpu APIC ID &
> version.)
>
> Variable acpi_lapic and its counterpart smp_found_config from MPS
> indicate whether it is SMP system, right? The following code:
>
>
> error = early_acpi_parse_madt_lapic_addr_ovr();
> if (!error) {
> acpi_lapic = 1;
> smp_found_config = 1;
> }
>
> means setting them when there is no override sub-table, so why can't
> moving the setting operation out? Another issue: if there *is* override
> sub-table, don't set those two?
>
Ping.
On 1/23/20 9:41 AM, Cao jin wrote:
> Logic in early_acpi_process_madt() & acpi_process_madt() is really hard to
> follow now. Clean them up.
>
> Done basic boot test on my x86-64 PC.
>
> CCed [email protected]
>
> Cao jin (2):
> x86/acpi: Improve code readablity of early madt processing
> x86/acpi: Cleanup acpi_process_madt()
>
> arch/x86/kernel/acpi/boot.c | 72 +++++++++++++++----------------------
> 1 file changed, 28 insertions(+), 44 deletions(-)
>
--
Sincerely,
Cao jin