Re: [PATCH v3] cxl/mce: Avoid alias page retirement for corrected errors

From: Shaikh Kamaluddin

Date: Thu Aug 27 2026 - 11:36:27 EST

On Tue, Aug 25, 2026 at 08:39:05AM -0700, Dave Jiang wrote:
>
>
> On 8/24/26 6:49 AM, Shaikh Kamaluddin wrote:
> > cxl_handle_mce() offlines the aliased page of an Extended Linear Cache
> > (ELC) region for any MCE with a usable address in the region. This
> > includes corrected errors, needlessly reducing usable memory.
> >
> > Skip ELC alias retirement when mce_is_correctable() identifies the
> > reported error as corrected. Uncorrected errors with a usable address
> > in the ELC region continue to retire the aliased page as before.
> >
> > mce_usable_address() already implements the per-vendor checks that
> > determine whether the reported address is usable, so no separate
> > memory-error classification is needed.
> >
> > On AMD, a corrected legacy bank 4 DRAM ECC error (XEC 8) reports a
> > usable address and retired the aliased page before this change.
> > Tested under QEMU with Intel Skylake-Server and AMD EPYC-Milan models.
> >
> > Fixes: 516e5bd0b6bf ("cxl: Add mce notifier to emit aliased address for extended linear cache")
> > Signed-off-by: Shaikh Kamaluddin <shaikhkamal2012@xxxxxxxxx>
>
> Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>

Thank you Dave for reviewing.

Regards,
Shaikh Kamaluddin

> > ---
> > Changelog:
> >
> > v2 -> v3:
> > - Drop the mce_is_memory_error() gate added in v2. On AMD it rejects
> > every non-UMC bank type, so poison-consumption records reported from
> > Load/Store or Data Fabric banks never reached mce_usable_address(),
> > which would have accepted them via MCA_STATUS[Poison]. (Sashiko)
> > - mce_usable_address() already implements the complete per-vendor
> > address-usability logic, so no separate memory-error classification
> > is needed.
> > - Add AMD test coverage (QEMU/TCG, EPYC-Milan) alongside the existing
> > Intel results.
> >
> > Link to v2: https://lore.kernel.org/linux-cxl/20260812151759.14390-1-shaikhkamal2012@xxxxxxxxx/
> >
> > v1 -> v2:
> > - Reworked commit message per review feedback
> > - Dropped redundant comment from the code
> >
> > Link to v1: https://lore.kernel.org/linux-cxl/20260810183013.47085-1-shaikhkamal2012@xxxxxxxxx/
> >
> > Reproduced under QEMU/vng. QEMU's cxl-type3 does not emulate the HMAT
> > extended-linear address_mode bit, so ELC was forced locally for testing
> > via a one-line debug hack in cxl_region_probe() (not part of this patch):
> >
> > if (!p->cache_size && p->res)
> > p->cache_size = resource_size(p->res) / 2;
> >
> > Steps:
> > 1. Boot with an Intel CPU model under TCG (KVM host-passthrough will
> > otherwise leak the host's real vendor ID, and AMD/SMCA takes a
> > different mce_usable_address() path, covered in the section below):
> >
> > vng -v -r ./arch/x86/boot/bzImage --disable-kvm --qemu-opts='-cpu Skylake-Server-v4,+mce,+mca -m 4G -machine q35,cxl=on -object memory-backend-ram,id=cxl-mem0,size=512M -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.0 -device cxl-rp,port=0,bus=cxl.0,id=root_port0,chassis=0,slot=0 -device cxl-type3,bus=root_port0,volatile-memdev=cxl-mem0,id=cxl-mem-device0 -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=512M'
> >
> > 2. modprobe mce-inject
> > $ cxl list -M
> > $ cxl list -D
> > $ cxl create-region -m mem0 -d decoder0.0 -w 1 -g 256 -t ram
> > $ dmesg | grep "DEBUG: forced cache_size"
> > $ modprobe device_dax
> > $ modprobe kmem
> > $ ls /sys/bus/dax/devices/
> > $ daxctl reconfigure-device dax0.0 --mode=system-ram
> > $ lsmem
> > RANGE SIZE STATE REMOVABLE BLOCK
> > 0x0000000000000000-0x000000007fffffff 2G online yes 0-15
> > 0x0000000100000000-0x000000017fffffff 2G online yes 32-47
> > 0x0000000190000000-0x00000001afffffff 512M online yes 50-53
> >
> > Memory block size: 128M
> > Total online memory: 4.5G
> > Total offline memory: 0B
> >
> > 3. Load the injector if not loaded earlier and derive the two MCi_STATUS values.
> >
> > # modprobe mce-inject
> >
> > MCi_STATUS bit layout used here (arch/x86/include/asm/mce.h):
> > bit 63 VAL - record valid
> > bit 61 UC - uncorrected (0 = corrected error under test)
> > bit 60 EN - error reporting enabled
> > bit 59 MISCV - MCi_MISC valid
> > bit 58 ADDRV - MCi_ADDR valid
> > bits[15:0] MCACOD - retained from the v2 test setup so the Intel
> > and AMD runs differ only in CPU model; not
> > consulted by this path.
> >
> > python3 -c "
> > VAL, UC, EN, MISCV, ADDRV = 1<<63, 1<<61, 1<<60, 1<<59, 1<<58
> > MCACOD_MEM = 1<<7
> > ce = VAL | EN | MISCV | ADDRV | MCACOD_MEM
> > uc = ce | UC
> > print(f'CE status = {hex(ce)}')
> > print(f'UC status = {hex(uc)}')"
> > # CE status = 0x9c00000000000080
> > # UC status = 0xbc00000000000080
> >
> > MCi_MISC: address-mode field, bits[8:6], must be 2 (physical):
> >
> > python3 -c "print(hex(2 << 6))"
> > # misc = 0x80
> >
> > 4. # cd /sys/kernel/debug/mce-inject
> > # echo sw > flags
> > # echo 0x9C00000000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190010000 > addr
> > # echo 9 > bank
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00000000000080 addr=0x190010000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > cxl_mce_debug: spa=0x190010000 contains=1
> > cxl_mce_debug: spa_alias=0x1a0010000 pfn=0x1a0010 pfn_valid=1
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0010000
> > Memory failure: 0x1a0010: recovery action for free buddy page: Recovered
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: 9c00000000000080
> > mce: [Hardware Error]: TSC a605ccda40 ADDR 190010000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 0:50654 TIME 1786375908 SOCKET 0 APIC 0 microcode 1
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 4 kB
> > ---------------------------------------
> >
> > CE without this patch:
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0010000
> > Memory failure: 0x1a0010: recovery action for free buddy page: Recovered
> > HardwareCorrupted: 4 kB
> > -------------------------------------
> >
> > CE with this patch:
> > (no "Offlining aliased SPA" message logged)
> > HardwareCorrupted: 0 kB
> >
> > # cd /sys/kernel/debug/mce-inject
> > # echo sw > flags
> > # echo 0x9C00000000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190010000 > addr
> > # echo 9 > bank
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00000000000080 addr=0x190010000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: 9c00000000000080
> > mce: [Hardware Error]: TSC 2eeae32fe0 ADDR 190010000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 0:50654 TIME 1786377156 SOCKET 0 APIC 0 microcode 1
> > clocksource: Watchdog remote CPU 11 read timed out
> >
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 0 kB
> > --------------------------------------
> >
> > For UC, same steps only status bit information will change :
> >
> > # cd /sys/kernel/debug/mce-inject
> > # echo sw > flags
> > # echo 0xbc00000000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190010000 > addr
> > # echo 9 > bank
> > # dmesg | grep cxl_mce_debug
> > # grep HardwareCorrupted /proc/meminfo
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0xbc00000000000080 addr=0x190010000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > cxl_mce_debug: spa=0x190010000 contains=1
> > cxl_mce_debug: spa_alias=0x1a0010000 pfn=0x1a0010 pfn_valid=1
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0010000
> > Memory failure: 0x1a0010: recovery action for free buddy page: Recovered
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: bc00000000000080
> > mce: [Hardware Error]: TSC e9dd2869e0 ADDR 190010000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 0:50654 TIME 1786377750 SOCKET 0 APIC 0 microcode 1
> >
> > Patched, UC: alias still offlined, confirming uncorrected handling is unchanged by this patch.
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0010000
> > Memory failure: 0x1a0010: recovery action for free buddy page: Recovered
> > HardwareCorrupted: 4 kB
> > -----------------------------------------------------------------------
> >
> > AMD Platform Testing:
> > ---------------------
> >
> > Note the vendor difference: on Intel, MISCV with MCi_MISC[8:6]=2 makes
> > any ADDRV record usable, so a plain CE is address-usable. On AMD an
> > address is usable only via poison, legacy bank-4 DRAM ECC, or PADDRV --
> > hence the differing usable= values for the same status word below.
> >
> >
> > vendor_id : AuthenticAMD
> > model name : AMD EPYC-Milan Processor
> >
> > -------------------------------------
> > Mainline Kernel Without this patch:
> > -------------------------------------
> >
> > vng -v -r ./arch/x86/boot/bzImage --disable-kvm --qemu-opts='-cpu EPYC-Milan -m 4G -machine q35,cxl=on -object memory-backend-ram,id=cxl-mem0,size=512M -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.0 -device cxl-rp,port=0,bus=cxl.0,id=root_port0,chassis=0,slot=0 -device cxl-type3,bus=root_port0,volatile-memdev=cxl-mem0,id=cxl-mem-device0 -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=512M'
> >
> > # cxl list -M
> > # cxl list -D
> > # cxl create-region -m mem0 -d decoder0.0 -w 1 -g 256 -t ram
> > # dmesg | grep "DEBUG: forced cache_size"
> > # modprobe device_dax
> > # modprobe kmem
> > # daxctl reconfigure-device dax0.0 --mode=system-ram
> >
> > # lsmem
> > RANGE SIZE STATE REMOVABLE BLOCK
> > 0x0000000000000000-0x000000007fffffff 2G online yes 0-15
> > 0x0000000100000000-0x000000017fffffff 2G online yes 32-47
> > 0x0000000190000000-0x00000001afffffff 512M online yes 50-53
> >
> > Memory block size: 128M
> > Total online memory: 4.5G
> > Total offline memory: 0B
> > Load Injector
> > # modprobe mce-inject
> > --------------------------------------------------------------------------------
> >
> > case1:
> >
> > label status addr bank note
> >
> > [LEGACY_B4_CE] 0x9c00000000080000 0x190070000 4 "case 3: bank4 XEC8 corrected+usable "[Before Patch]
> > ---------------------------------------------------------------------------------------------------------------------
> >
> > # cd /sys/kernel/debug/mce-inject
> > # echo sw > flags
> > # echo 0x9c00000000080000 > status
> > # echo 0x80 > misc
> > # echo 0x190070000 > addr
> > # echo 4 > bank
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00000000080000 addr=0x190070000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > cxl_mce_debug: spa=0x190070000 contains=1
> > cxl_mce_debug: spa_alias=0x1a0070000 pfn=0x1a0070 pfn_valid=1
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0070000
> > Memory failure: 0x1a0070: recovery action for free buddy page: Recovered
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 4: 9c00000000080000
> > mce: [Hardware Error]: TSC cbdf882d20 ADDR 190070000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787479138 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 4 kB
> > --------------------------------------------------------------------------------------------
> >
> > case2:
> > label status addr bank note
> >
> > [POISON] 0x9c00080000000080 0x190040000 9 "case 2: poison only (UC=0) - divergence to note"[Before Patch]
> > -----------------------------------------------------------------------------------------------------------------------
> >
> > # echo sw > flags
> > # echo 0x9c00080000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190040000 > addr
> > # echo 9 > bank
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00080000000080 addr=0x190040000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > cxl_mce_debug: spa=0x190040000 contains=1
> > cxl_mce_debug: spa_alias=0x1a0040000 pfn=0x1a0040 pfn_valid=1
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0040000
> > Memory failure: 0x1a0040: recovery action for free buddy page: Recovered
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: 9c00080000000080
> > mce: [Hardware Error]: TSC 17153949200 ADDR 190040000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787479277 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 8 kB (cumulative added previous 4kb + 4kb this test)
> > -----------------------------------------------
> >
> > AMD Platform Testing with applied patch:
> > ------------------------------------------
> >
> > # cxl list -D
> > # cxl create-region -m mem0 -d decoder0.0 -w 1 -g 256 -t ram
> > # dmesg | grep "DEBUG: forced cache_size"
> > # modprobe device_dax
> > # modprobe kmem
> > # daxctl reconfigure-device dax0.0 --mode=system-ram
> > # lsmem
> > # modprobe mce-inject
> > ----------------------------------------------------
> >
> > case1:
> > label status addr bank note
> >
> > [ CE] 0x9c00000000000080 0x190010000 9 "case 1: corrected, no usable addr"
> > ----------------------------------------------------------------------------------------
> >
> > # cd /sys/kernel/debug/mce-inject
> > # echo sw > flags
> > # echo 0x9c00000000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190010000 > addr
> > # echo 9 > bank
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00000000000080 addr=0x190010000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=0
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: 9c00000000000080
> > mce: [Hardware Error]: TSC 8e59f2f3bc0 ADDR 190010000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787454918 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 0 kB
> > -------------------------------------------------------------------------
> >
> > case2:
> > label status addr bank note
> > [ UC ] 0xbc00000000000080 0x190020000 9 "case 1: uncorrected, no poison -> unusable"
> > -------------------------------------------------------------------------------------------------
> >
> > cd /sys/kernel/debug/mce-inject
> > echo sw > flags
> > echo 0xbc00000000000080 > status
> > echo 0x80 > misc
> > echo 0x190020000 > addr
> > echo 9 > bank
> > Result:
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0xbc00000000000080 addr=0x190020000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=0
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: bc00000000000080
> > mce: [Hardware Error]: TSC 134d6de13240 ADDR 190020000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787460569 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 0 kB
> > -------------------------------------------------------------------
> >
> > case3:
> > label status addr bank note
> >
> > [ POISON ] 0x9c00080000000080 0x190040000 9 "case 2: poison only (UC=0) - divergence to note"
> > ------------------------------------------------------------------------------------------------------------
> >
> > # cd /sys/kernel/debug/mce-inject
> > # echo sw > flags
> > # echo 0x9c00080000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190040000 > addr
> > # echo 9 > bank
> > Result:
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00080000000080 addr=0x190040000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: 9c00080000000080
> > mce: [Hardware Error]: TSC 14e29da617c0 ADDR 190040000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787463321 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 0 kB
> > ------------------------------------------
> >
> > case4:
> > label status addr bank note
> >
> > [ DEFERRED ] 0x9c00100000000080 0x190020000 9 "case 1: deferred, no poison -> unusable"
> > ------------------------------------------------------------------------------------------------
> >
> > # echo sw > flags
> > # echo 0x9c00100000000080 > status
> > # echo 0x80 > misc
> > #echo 0x190020000 > addr
> > #echo 9 > bank
> > Result:
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00100000000080 addr=0x190020000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=0
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: 9c00100000000080
> > mce: [Hardware Error]: TSC 9a2d801ff40 ADDR 190020000
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787456818 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 0 kB
> > -----------------------------------------------
> >
> > case5:
> > label status addr bank note
> >
> > [ DEF_POISON ] 0x9c00180000000080 0x190060000 9 "case 2: deferred+poison - MUST be handled"
> > --------------------------------------------------------------------------------------------------------
> >
> > # echo sw > flags
> > # echo 0x9c00180000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190060000 > addr
> > # echo 9 > bank
> > Result:
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00180000000080 addr=0x190060000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > cxl_mce_debug: spa=0x190060000 contains=1
> > cxl_mce_debug: spa_alias=0x1a0060000 pfn=0x1a0060 pfn_valid=1
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0060000
> > Memory failure: 0x1a0060: recovery action for free buddy page: Recovered
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: 9c00180000000080
> > mce: [Hardware Error]: TSC a60fd45ae60 ADDR 190060000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787457072 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 4 kB
> > -----------------------------------
> >
> > case6:
> > label status addr bank note
> >
> > [UC_POISON] 0xbc00080000000080 0x190050000 9 "case 2: poison consumption - MUST be handled"
> > --------------------------------------------------------------------------------------------------------
> >
> > # echo sw > flags
> > # echo 0xbc00080000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190050000 > addr
> > # echo 9 > bank
> >
> > Resul:
> >
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0xbc00080000000080 addr=0x190050000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > cxl_mce_debug: spa=0x190050000 contains=1
> > cxl_mce_debug: spa_alias=0x1a0050000 pfn=0x1a0050 pfn_valid=1
> > cxl_region region0: Offlining aliased SPA address0: 0x1a0050000
> > Memory failure: 0x1a0050: recovery action for free buddy page: Recovered
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: bc00080000000080
> > mce: [Hardware Error]: TSC f03abeed540 ADDR 190050000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787457328 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 4 kB
> > -------------------------------------------------------------------------------------
> >
> > case7:
> > label status addr bank note
> >
> > [B4_NONMEM_POISON] 0x9c00080000000080 0x190080000 4 "case 3 override: bank4 non-mem, poison ignored"
> > -------------------------------------------------------------------------------------------------------------------
> >
> > # echo sw > flags
> > # echo 0x9c00080000000080 > status
> > # echo 0x80 > misc
> > # echo 0x190080000 > addr
> > # echo 4 > bank
> >
> > Result:
> >
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00080000000080 addr=0x190080000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=0
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 4: 9c00080000000080
> > mce: [Hardware Error]: TSC 21c66cecf80 ADDR 190080000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787454082 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 0 kB
> > --------------------------------------------------------------------------------------------
> >
> > case8:
> > label status addr bank note
> >
> > [LEGACY_B4_CE] 0x9c00000000080000 0x190070000 4 "case 3: bank4 XEC8 corrected+usable - THE FIX"
> > -------------------------------------------------------------------------------------------------------------------
> >
> > echo sw > flags
> > echo 0x9c00000000080000 > status
> > echo 0x80 > misc
> > echo 0x190070000 > addr
> > echo 4 > bank
> >
> > result:
> > -------
> >
> > mce: [Hardware Error]: Machine check events logged
> > cxl_mce_debug: entered status=0x9c00000000080000 addr=0x190070000 cache_size=0x10000000 res=[mem 0x190000000-0x1afffffff flags 0x200] usable=1
> > mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 4: 9c00000000080000
> > mce: [Hardware Error]: TSC 3610305ed80 ADDR 190070000 MISC 80
> > mce: [Hardware Error]: PROCESSOR 2:a00f11 TIME 1787454482 SOCKET 0 APIC 0 microcode 1000065
> > # grep HardwareCorrupted /proc/meminfo
> > HardwareCorrupted: 0 kB
> > -------------------------------------------
> >
> > Note: an AMD record with MCI_STATUS_POISON set but UC and Deferred
> > clear is filtered by this patch where it previously was not. Per AMD64
> > APM 24593 Rev 3.45, when UC is clear the error class is determined
> > solely by the Deferred bit, and Poison qualifies an uncorrected error
> > rather than establishing one. Real poison is therefore always reported
> > with Deferred set (not yet consumed) or UC set (consumed via #MC), and
> > both of those cases still retire the alias. Poison with UC and Deferred
> > both clear is not a valid encoding and appears only under software
> > injection.
> >
> > drivers/cxl/core/mce.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/cxl/core/mce.c b/drivers/cxl/core/mce.c
> > index 65fed913b221..3ac6802e750d 100644
> > --- a/drivers/cxl/core/mce.c
> > +++ b/drivers/cxl/core/mce.c
> > @@ -18,7 +18,13 @@ static int cxl_handle_mce(struct notifier_block *nb, unsigned long val,
> > u64 spa, spa_alias;
> > unsigned long pfn;
> >
> > - if (!mce || !mce_usable_address(mce))
> > + if (!mce)
> > + return NOTIFY_DONE;
> > +
> > + if (mce_is_correctable(mce))
> > + return NOTIFY_DONE;
> > +
> > + if (!mce_usable_address(mce))
> > return NOTIFY_DONE;
> >
> > spa = mce->addr & MCI_ADDR_PHYSADDR;
> >
> > base-commit: 7098e9cd98a05c0c5de2fae0c2465f9d966fdd07
>