[PATCH v2 0/3] Support additional AMD EILVT registers

[PATCH v2 0/3] Support additional AMD EILVT registers

[Naveen N Rao (AMD)]

This is v2 of the series posted at:
http://lore.kernel.org/r/cover.1775019269.git.naveen@kernel.org

Changes since v1:
- Drop the first two patches that were merged
- Call init_eilvt() from apic_bsp_setup(), rather than 
  setup_local_APIC() so as not to call an __init function from a 
  non-init function. (Kernel 0-day bot)
- Initialize eilvt count to APIC_EILVT_NR_AMD_10H and allocate 
  eilvt_offsets array only on AMD processors.
 
Manali,
I am retaining your Tested-by: tag since the changes are minimal, but 
please reply here if you have concerns with the changes.

--
Future AMD processors will be increasing the number of APIC EILVT 
registers (*). This series adds support for the same along with some 
related cleanups.

(*) https://docs.amd.com/v/u/en-US/69205_1.00_AMD64_IBS_PUB)


- Naveen


Naveen N Rao (AMD) (3):
  perf/amd/ibs: Limit the max EILVT register count for AMD family 0x10
  x86/apic: Introduce a variable to track the number of EILVT registers
  x86/apic: Drop APIC_EILVT_NR_MAX and switch to using apic_eilvt_count

 arch/x86/include/asm/apic.h    |  2 ++
 arch/x86/include/asm/apicdef.h |  2 +-
 arch/x86/events/amd/ibs.c      |  4 ++--
 arch/x86/kernel/apic/apic.c    | 19 +++++++++++++++++--
 4 files changed, 22 insertions(+), 5 deletions(-)


base-commit: 70e7aca9f7ff4d1bee94c5b04973c3dbca1dba00
-- 
2.54.0

[PATCH v2 1/3] perf/amd/ibs: Limit the max EILVT register count for AMD family 0x10

[Naveen N Rao (AMD)]

For AMD family 0x10, EILVT offsets are not assigned by BIOS and is
instead assigned by picking the next available EILVT offset.  Use the
maximum EILVT count for family 0x10 (APIC_EILVT_NR_AMD_10H) rather than
an arbitrary maximum EILVT count when looking for the next available
EILVT offset.

Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
Tested-by: Manali Shukla <manali.shukla@amd.com>
---
 arch/x86/events/amd/ibs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 20c2de5c697b..ad73a002f8cd 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -1839,13 +1839,13 @@ static void force_ibs_eilvt_setup(void)
 
 	preempt_disable();
 	/* find the next free available EILVT entry, skip offset 0 */
-	for (offset = 1; offset < APIC_EILVT_NR_MAX; offset++) {
+	for (offset = 1; offset < APIC_EILVT_NR_AMD_10H; offset++) {
 		if (get_eilvt(offset))
 			break;
 	}
 	preempt_enable();
 
-	if (offset == APIC_EILVT_NR_MAX) {
+	if (offset == APIC_EILVT_NR_AMD_10H) {
 		pr_debug("No EILVT entry available\n");
 		return;
 	}
-- 
2.54.0

[PATCH v2 2/3] x86/apic: Introduce a variable to track the number of EILVT registers

[Naveen N Rao (AMD)]

Future AMD processors will be increasing the number of EILVT registers.
Rather than hardcoding the maximum EILVT register count and using that
everywhere, introduce a variable to track the EILVT register count.

The number of EILVT registers is exposed through the extended APIC
Feature Register (APIC_EFEAT) bits 23:16. Use this to initialize the
count and fall back to the current default (APIC_EILVT_NR_AMD_10H) if
the count is not available.

Export the new variable for KVM since it needs this for supporting
extended APIC register space on AMD.

Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
Tested-by: Manali Shukla <manali.shukla@amd.com>
---
http://lore.kernel.org/r/20260204074452.55453-3-manali.shukla@amd.com as 
a related series adding support for KVM and needing access to the EILVT 
register count.

- Naveen


 arch/x86/include/asm/apic.h    |  2 ++
 arch/x86/include/asm/apicdef.h |  1 +
 arch/x86/kernel/apic/apic.c    | 12 ++++++++++++
 3 files changed, 15 insertions(+)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 9cd493d467d4..8b03c7a14706 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -74,6 +74,8 @@ enum apic_intr_mode_id {
 	APIC_SYMMETRIC_IO_NO_ROUTING
 };
 
+extern unsigned int apic_eilvt_count;
+
 /*
  * With 82489DX we can't rely on apic feature bit
  * retrieved via cpuid but still have to deal with
diff --git a/arch/x86/include/asm/apicdef.h b/arch/x86/include/asm/apicdef.h
index bc125c4429dc..ba7657e75ad1 100644
--- a/arch/x86/include/asm/apicdef.h
+++ b/arch/x86/include/asm/apicdef.h
@@ -134,6 +134,7 @@
 #define		APIC_TDR_DIV_64		0x9
 #define		APIC_TDR_DIV_128	0xA
 #define	APIC_EFEAT	0x400
+#define		APIC_EFEAT_XLC(x)	(((x) >> 16) & 0xff)
 #define	APIC_ECTRL	0x410
 #define APIC_SEOI	0x420
 #define APIC_IER	0x480
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 8c614750a19b..ecbf15399399 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -342,6 +342,8 @@ static void __setup_APIC_LVTT(unsigned int clocks, int oneshot, int irqen)
  */
 
 static atomic_t eilvt_offsets[APIC_EILVT_NR_MAX];
+unsigned int apic_eilvt_count __ro_after_init;
+EXPORT_SYMBOL_FOR_KVM(apic_eilvt_count);
 
 static inline int eilvt_entry_is_changeable(unsigned int old, unsigned int new)
 {
@@ -410,6 +412,15 @@ int setup_APIC_eilvt(u8 offset, u8 vector, u8 msg_type, u8 mask)
 }
 EXPORT_SYMBOL_GPL(setup_APIC_eilvt);
 
+static __init void init_eilvt(void)
+{
+	if (cpu_feature_enabled(X86_FEATURE_EXTAPIC))
+		apic_eilvt_count = APIC_EFEAT_XLC(apic_read(APIC_EFEAT));
+
+	if (!apic_eilvt_count && boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
+		apic_eilvt_count = APIC_EILVT_NR_AMD_10H;
+}
+
 /*
  * Program the next event, relative to now
  */
@@ -2344,6 +2355,7 @@ static void __init apic_bsp_setup(bool upmode)
 	if (upmode)
 		apic_bsp_up_setup();
 	setup_local_APIC();
+	init_eilvt();
 
 	enable_IO_APIC();
 	end_local_APIC_setup();
-- 
2.54.0

[PATCH v2 3/3] x86/apic: Drop APIC_EILVT_NR_MAX and switch to using apic_eilvt_count

[Naveen N Rao (AMD)]

Switch to using apic_eilvt_count as the maximum EILVT register count.
Since this value is no longer a compile-time constant, update
eilvt_offsets to be dynamically allocated.

Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
Tested-by: Manali Shukla <manali.shukla@amd.com>
---
 arch/x86/include/asm/apicdef.h | 1 -
 arch/x86/kernel/apic/apic.c    | 7 +++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/apicdef.h b/arch/x86/include/asm/apicdef.h
index ba7657e75ad1..32a242ae0455 100644
--- a/arch/x86/include/asm/apicdef.h
+++ b/arch/x86/include/asm/apicdef.h
@@ -140,7 +140,6 @@
 #define APIC_IER	0x480
 #define APIC_EILVTn(n)	(0x500 + 0x10 * n)
 #define		APIC_EILVT_NR_AMD_10H	4
-#define		APIC_EILVT_NR_MAX	APIC_EILVT_NR_AMD_10H
 
 #define APIC_BASE (fix_to_virt(FIX_APIC_BASE))
 #define APIC_BASE_MSR		0x800
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index ecbf15399399..0313989e1632 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -341,7 +341,7 @@ static void __setup_APIC_LVTT(unsigned int clocks, int oneshot, int irqen)
  * necessarily a BIOS bug.
  */
 
-static atomic_t eilvt_offsets[APIC_EILVT_NR_MAX];
+static atomic_t *eilvt_offsets;
 unsigned int apic_eilvt_count __ro_after_init;
 EXPORT_SYMBOL_FOR_KVM(apic_eilvt_count);
 
@@ -356,7 +356,7 @@ static unsigned int reserve_eilvt_offset(int offset, unsigned int new)
 {
 	unsigned int rsvd, vector;
 
-	if (offset >= APIC_EILVT_NR_MAX)
+	if (!eilvt_offsets || offset >= apic_eilvt_count)
 		return ~0;
 
 	rsvd = atomic_read(&eilvt_offsets[offset]);
@@ -419,6 +419,9 @@ static __init void init_eilvt(void)
 
 	if (!apic_eilvt_count && boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
 		apic_eilvt_count = APIC_EILVT_NR_AMD_10H;
+
+	if (apic_eilvt_count)
+		eilvt_offsets = kzalloc_objs(atomic_t, apic_eilvt_count);
 }
 
 /*
-- 
2.54.0

Re: [PATCH v2 0/3] Support additional AMD EILVT registers

[Bharata B Rao]

On 12-May-26 7:49 PM, Naveen N Rao (AMD) wrote:
> This is v2 of the series posted at:
> http://lore.kernel.org/r/cover.1775019269.git.naveen@kernel.org
> 
> Changes since v1:
> - Drop the first two patches that were merged
> - Call init_eilvt() from apic_bsp_setup(), rather than 
>   setup_local_APIC() so as not to call an __init function from a 
>   non-init function. (Kernel 0-day bot)
> - Initialize eilvt count to APIC_EILVT_NR_AMD_10H and allocate 
>   eilvt_offsets array only on AMD processors.
>  
> Manali,
> I am retaining your Tested-by: tag since the changes are minimal, but 
> please reply here if you have concerns with the changes.
> 
> --
> Future AMD processors will be increasing the number of APIC EILVT 
> registers (*). This series adds support for the same along with some 
> related cleanups.
> 
> (*) https://docs.amd.com/v/u/en-US/69205_1.00_AMD64_IBS_PUB)

This patchset is required to support IBS Memory Profiler feature too. This
patchset got tested with pghot+IBS Memory profiler -
https://lore.kernel.org/linux-mm/20260504060924.344313-8-bharata@amd.com/

Regards,
Bharata.