KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 157 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-dwc-pcie b/Documentation/ABI/testing/debugfs-dwc-pcie
new file mode 100644
index 000000000..92b76f52a
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-dwc-pcie
@@ -0,0 +1,157 @@
+What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_debug/lane_detect
+Date:		February 2025
+Contact:	Shradha Todi <shradha.t@samsung.com>
+Description:	(RW) Write the lane number to be checked for detection.	Read
+		will return whether PHY indicates receiver detection on the
+		selected lane. The default selected lane is Lane0.
+
+What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_debug/rx_valid
+Date:		February 2025
+Contact:	Shradha Todi <shradha.t@samsung.com>
+Description:	(RW) Write the lane number to be checked as valid or invalid.
+		Read will return the status of PIPE RXVALID signal of the
+		selected lane. The default selected lane is Lane0.
+
+What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_err_inj/<error>
+Date:		February 2025
+Contact:	Shradha Todi <shradha.t@samsung.com>
+Description:	The "rasdes_err_inj" is a directory which can be used to inject
+		errors into the system. The possible errors that can be injected
+		are:
+
+		  1) tx_lcrc            - TLP LCRC error injection TX Path
+		  2) b16_crc_dllp       - 16b CRC error injection of ACK/NAK DLLP
+		  3) b16_crc_upd_fc     - 16b CRC error injection of Update-FC DLLP
+		  4) tx_ecrc            - TLP ECRC error injection TX Path
+		  5) fcrc_tlp           - TLP's FCRC error injection TX Path
+		  6) parity_tsos        - Parity error of TSOS
+		  7) parity_skpos       - Parity error on SKPOS
+		  8) rx_lcrc            - LCRC error injection RX Path
+		  9) rx_ecrc            - ECRC error injection RX Path
+		  10) tlp_err_seq       - TLPs SEQ# error
+		  11) ack_nak_dllp_seq  - DLLPS ACK/NAK SEQ# error
+		  12) ack_nak_dllp      - ACK/NAK DLLPs transmission block
+		  13) upd_fc_dllp       - UpdateFC DLLPs transmission block
+		  14) nak_dllp          - Always transmission for NAK DLLP
+		  15) inv_sync_hdr_sym  - Invert SYNC header
+		  16) com_pad_ts1       - COM/PAD TS1 order set
+		  17) com_pad_ts2       - COM/PAD TS2 order set
+		  18) com_fts           - COM/FTS FTS order set
+		  19) com_idl           - COM/IDL E-idle order set
+		  20) end_edb           - END/EDB symbol
+		  21) stp_sdp           - STP/SDP symbol
+		  22) com_skp           - COM/SKP SKP order set
+		  23) posted_tlp_hdr    - Posted TLP Header credit value control
+		  24) non_post_tlp_hdr  - Non-Posted TLP Header credit value control
+		  25) cmpl_tlp_hdr      - Completion TLP Header credit value control
+		  26) posted_tlp_data   - Posted TLP Data credit value control
+		  27) non_post_tlp_data - Non-Posted TLP Data credit value control
+		  28) cmpl_tlp_data     - Completion TLP Data credit value control
+		  29) duplicate_tlp     - Generates duplicate TLPs
+		  30) nullified_tlp     - Generates Nullified TLPs
+
+		(WO) Write to the attribute will prepare controller to inject
+		the respective error in the next transmission of data.
+
+		Parameter required to write will change in the following ways:
+
+		- Errors 9 and 10 are sequence errors. The write command:
+
+		    echo <count> <diff> > /sys/kernel/debug/dwc_pcie_<dev>/rasdes_err_inj/<error>
+
+		    <count>
+			    Number of errors to be injected
+		    <diff>
+			    The difference to add or subtract from natural
+			    sequence number to generate sequence error.
+			    Allowed range from -4095 to 4095
+
+		- Errors 23 to 28 are credit value error insertions. The write
+		  command:
+
+		    echo <count> <diff> <vc> > /sys/kernel/debug/dwc_pcie_<dev>/rasdes_err_inj/<error>
+
+		    <count>
+			    Number of errors to be injected
+		    <diff>
+			    The difference to add or subtract from UpdateFC
+			    credit value. Allowed range from -4095 to 4095
+		    <vc>
+			    Target VC number
+
+		- All other errors. The write command:
+
+		    echo <count> > /sys/kernel/debug/dwc_pcie_<dev>/rasdes_err_inj/<error>
+
+		    <count>
+			    Number of errors to be injected
+
+What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_event_counters/<event>/counter_enable
+Date:		February 2025
+Contact:	Shradha Todi <shradha.t@samsung.com>
+Description:	The "rasdes_event_counters" is the directory which can be used
+		to collect statistical data about the number of times a certain
+		event has occurred in the controller. The list of possible
+		events are:
+
+		1) EBUF Overflow
+		2) EBUF Underrun
+		3) Decode Error
+		4) Running Disparity Error
+		5) SKP OS Parity Error
+		6) SYNC Header Error
+		7) Rx Valid De-assertion
+		8) CTL SKP OS Parity Error
+		9) 1st Retimer Parity Error
+		10) 2nd Retimer Parity Error
+		11) Margin CRC and Parity Error
+		12) Detect EI Infer
+		13) Receiver Error
+		14) RX Recovery Req
+		15) N_FTS Timeout
+		16) Framing Error
+		17) Deskew Error
+		18) Framing Error In L0
+		19) Deskew Uncompleted Error
+		20) Bad TLP
+		21) LCRC Error
+		22) Bad DLLP
+		23) Replay Number Rollover
+		24) Replay Timeout
+		25) Rx Nak DLLP
+		26) Tx Nak DLLP
+		27) Retry TLP
+		28) FC Timeout
+		29) Poisoned TLP
+		30) ECRC Error
+		31) Unsupported Request
+		32) Completer Abort
+		33) Completion Timeout
+		34) EBUF SKP Add
+		35) EBUF SKP Del
+
+		(RW) Write 1 to enable the event counter and write 0 to disable
+		the event counter. Read will return whether the counter is
+		currently enabled or disabled. Counter is disabled by default.
+
+What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_event_counters/<event>/counter_value
+Date:		February 2025
+Contact:	Shradha Todi <shradha.t@samsung.com>
+Description:	(RO) Read will return the current value of the event counter.
+		To reset the counter, counter should be disabled first and then
+		enabled back using the "counter_enable" attribute.
+
+What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_event_counters/<event>/lane_select
+Date:		February 2025
+Contact:	Shradha Todi <shradha.t@samsung.com>
+Description:	(RW) Some lanes in the event list are lane specific events.
+		These include events from 1 to 11, as well as, 34 and 35. Write
+		the lane number for which you wish the counter to be enabled,
+		disabled, or value dumped. Read will return the current
+		selected lane number. Lane0 is selected by default.
+
+What:		/sys/kernel/debug/dwc_pcie_<dev>/ltssm_status
+Date:		February 2025
+Contact:	Hans Zhang <18255117159@163.com>
+Description:	(RO) Read will return the current PCIe LTSSM state in both
+		string and raw value.