linux-kernel - Re: [PATCH v2] EDAC/amd64: Fix possible module load failure on some UMC usage combinations

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Message-ID: <20241211185109.GFZ1nfHQBJB4rdXXSI@fat_crate.local>
Date: Wed, 11 Dec 2024 19:51:09 +0100
From: Borislav Petkov <bp@...en8.de>
To: Yazen Ghannam <yazen.ghannam@....com>
Cc: Avadhut Naik <avadhut.naik@....com>, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] EDAC/amd64: Fix possible module load failure on some
 UMC usage combinations

On Wed, Dec 11, 2024 at 10:46:37AM -0500, Yazen Ghannam wrote:
> Looks good overall. We can even remove the "nid" variable and just use
> "pvt->mc_node_id" directly in the debug message. This is another remnant
> from when this function did register accesses.

Ok, done.

Avadhut, can you pls verify this fixes your issue too?

I'll run it on my boxes too, to make sure nothing breaks.

Thx.

---
From: "Borislav Petkov (AMD)" <bp@...en8.de>
Date: Wed, 11 Dec 2024 12:07:42 +0100
Subject: [PATCH] EDAC/amd64: Simplify ECC check on unified memory controllers

The intent of the check is to see whether at least one UMC has ECC
enabled. So do that instead of tracking which ones are enabled in masks
which are too small in size anyway and lead to not loading the driver on
Zen4 machines with UMCs enabled over UMC8.

Fixes: e2be5955a886 ("EDAC/amd64: Add support for AMD Family 19h Models 10h-1Fh and A0h-AFh")
Reported-by: Avadhut Naik <avadhut.naik@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Cc: <stable@...nel.org>
Link: https://lore.kernel.org/r/20241210212054.3895697-1-avadhut.naik@amd.com
---
 drivers/edac/amd64_edac.c | 32 ++++++++++----------------------
 1 file changed, 10 insertions(+), 22 deletions(-)

diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index ddfbdb66b794..5d356b7c4589 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -3362,36 +3362,24 @@ static bool dct_ecc_enabled(struct amd64_pvt *pvt)
 
 static bool umc_ecc_enabled(struct amd64_pvt *pvt)
 {
-	u8 umc_en_mask = 0, ecc_en_mask = 0;
-	u16 nid = pvt->mc_node_id;
 	struct amd64_umc *umc;
-	u8 ecc_en = 0, i;
+	bool ecc_en = false;
+	int i;
 
+	/* Check whether at least one UMC is enabled: */
 	for_each_umc(i) {
 		umc = &pvt->umc[i];
 
-		/* Only check enabled UMCs. */
-		if (!(umc->sdp_ctrl & UMC_SDP_INIT))
-			continue;
-
-		umc_en_mask |= BIT(i);
-
-		if (umc->umc_cap_hi & UMC_ECC_ENABLED)
-			ecc_en_mask |= BIT(i);
+		if (umc->sdp_ctrl & UMC_SDP_INIT &&
+		    umc->umc_cap_hi & UMC_ECC_ENABLED) {
+			ecc_en = true;
+			break;
+		}
 	}
 
-	/* Check whether at least one UMC is enabled: */
-	if (umc_en_mask)
-		ecc_en = umc_en_mask == ecc_en_mask;
-	else
-		edac_dbg(0, "Node %d: No enabled UMCs.\n", nid);
-
-	edac_dbg(3, "Node %d: DRAM ECC %s.\n", nid, (ecc_en ? "enabled" : "disabled"));
+	edac_dbg(3, "Node %d: DRAM ECC %s.\n", pvt->mc_node_id, (ecc_en ? "enabled" : "disabled"));
 
-	if (!ecc_en)
-		return false;
-	else
-		return true;
+	return ecc_en;
 }
 
 static inline void
-- 
2.43.0

-- 
Regards/Gruss,
    Boris.

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