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When the HDM decoder capability is globally enabled, >> ignore DVSEC range registers regardless of individual decoder commit >> state. >> >> should_emulate_decoders() currently loops over per-decoder COMMITTED >> bits, which leads to an incorrect DVSEC fallback when those bits are >> zero. One way to trigger this is to destroy a region and bounce the >> memdev: >> >> cxl disable-region region0 >> cxl destroy-region region0 >> cxl disable-memdev mem0 >> cxl enable-memdev mem0 >> >> Region teardown zeroes the HDM decoder registers including the committed >> bits. The subsequent memdev re-probe finds uncommitted decoders and falls >> back to DVSEC emulation, even though HDM remains globally enabled. >> >> Observed failures: >> >> should_emulate_decoders: cxl_port endpoint6: decoder6.0: committed: 0 base: 0x0_00000000 size: 0x0_00000000 >> devm_cxl_setup_hdm: cxl_port endpoint6: Fallback map 1 range register >> .. >> devm_cxl_add_region: cxl_acpi ACPI0017:00: decoder0.0: created region0 >> __construct_region: cxl_pci 0000:e1:00.0: mem1:decoder6.0: >> __construct_region region0 res: [mem 0x850000000-0x284fffffff flags 0x200] iw: 1 ig: 4096 >> cxl region0: pci0000:e0:port1 cxl_port_setup_targets expected iw: 1 ig: 4096 .. >> cxl region0: pci0000:e0:port1 cxl_port_setup_targets got iw: 1 ig: 256 state: disabled .. >> cxl_port endpoint6: failed to attach decoder6.0 to region0: -6 >> .. >> devm_cxl_add_region: cxl_acpi ACPI0017:00: decoder0.0: created region4 >> alloc_hpa: cxl region4: HPA allocation error (-34) .. >> >> Fixes: 52cc48ad2a76 ("cxl/hdm: Limit emulation to the number of range registers") >> Signed-off-by: Smita Koralahalli >> Reviewed-by: Dan Williams > > Smita, > > Applied to cxl/fixes > 75cea0776de5 cxl/hdm: Avoid incorrect DVSEC fallback when HDM decoders are enabled > > Any chance to add the issue reproduce steps to a regression test script in CXL CLI test please? Thanks! Thank you! Okay I will add it. That should be in ndctl/test? Thanks Smita > >> --- >> v2: >> Reworded commit message to focus on root cause per Dan's feedback. >> Dropped downstream details (IG/construct_region/hpa_alloc) >> Added error signatures. >> Link to v1: https://lore.kernel.org/r/20260212223800.23624-1-Smita.KoralahalliChannabasappa@amd.com >> --- >> drivers/cxl/core/hdm.c | 25 +++++++++---------------- >> 1 file changed, 9 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c >> index c222e98ae736..cb5d5a047a9d 100644 >> --- a/drivers/cxl/core/hdm.c >> +++ b/drivers/cxl/core/hdm.c >> @@ -94,7 +94,6 @@ static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info) >> struct cxl_hdm *cxlhdm; >> void __iomem *hdm; >> u32 ctrl; >> - int i; >> >> if (!info) >> return false; >> @@ -113,22 +112,16 @@ static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info) >> return false; >> >> /* >> - * If any decoders are committed already, there should not be any >> - * emulated DVSEC decoders. >> + * If HDM decoders are globally enabled, do not fall back to DVSEC >> + * range emulation. Zeroed decoder registers after region teardown >> + * do not imply absence of HDM capability. >> + * >> + * Falling back to DVSEC here would treat the decoder as AUTO and >> + * may incorrectly latch default interleave settings. >> */ >> - for (i = 0; i < cxlhdm->decoder_count; i++) { >> - ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(i)); >> - dev_dbg(&info->port->dev, >> - "decoder%d.%d: committed: %ld base: %#x_%.8x size: %#x_%.8x\n", >> - info->port->id, i, >> - FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl), >> - readl(hdm + CXL_HDM_DECODER0_BASE_HIGH_OFFSET(i)), >> - readl(hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(i)), >> - readl(hdm + CXL_HDM_DECODER0_SIZE_HIGH_OFFSET(i)), >> - readl(hdm + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(i))); >> - if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl)) >> - return false; >> - } >> + ctrl = readl(hdm + CXL_HDM_DECODER_CTRL_OFFSET); >> + if (ctrl & CXL_HDM_DECODER_ENABLE) >> + return false; >> >> return true; >> } >> >> base-commit: 93d0fcdddc9e7be9d4f42acbe57bc90dbb0fe75d >