linux-kernel - [PATCH] crypto: ccp: do not request interrupt on cmd completion when irqs disabled

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Message-ID: <20240829102007.34355-1-amit@kernel.org>
Date: Thu, 29 Aug 2024 12:20:07 +0200
From: Amit Shah <amit@...nel.org>
To: ashish.kalra@....com,
	thomas.lendacky@....com,
	bp@...en8.de,
	john.allen@....com,
	herbert@...dor.apana.org.au,
	davem@...emloft.net,
	michael.roth@....com,
	linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org
Cc: amit.shah@....com
Subject: [PATCH] crypto: ccp: do not request interrupt on cmd completion when irqs disabled

From: Amit Shah <amit.shah@....com>

While sending a command to the PSP, we always requested an interrupt
from the PSP after command completion.  This worked for most cases.  For
the special case of irqs being disabled -- e.g. when running within
crashdump or kexec contexts, we should not set the SEV_CMDRESP_IOC flag,
so the PSP knows to not attempt interrupt delivery.

Fixes: 8ef979584ea8 ("crypto: ccp: Add panic notifier for SEV/SNP firmware shutdown on kdump")

Based-on-patch-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Amit Shah <amit.shah@....com>
---
 drivers/crypto/ccp/sev-dev.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 9810edbb272d..1775bac7f597 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -910,7 +910,18 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 
 	sev->int_rcvd = 0;
 
-	reg = FIELD_PREP(SEV_CMDRESP_CMD, cmd) | SEV_CMDRESP_IOC;
+	reg = FIELD_PREP(SEV_CMDRESP_CMD, cmd);
+
+	/*
+	 * If invoked during panic handling, local interrupts are disabled so
+	 * the PSP command completion interrupt can't be used.
+	 * sev_wait_cmd_ioc() already checks for interrupts disabled and
+	 * polls for PSP command completion.  Ensure we do not request an
+	 * interrupt from the PSP if irqs disabled.
+	 */
+	if (!irqs_disabled())
+		reg |= SEV_CMDRESP_IOC;
+
 	iowrite32(reg, sev->io_regs + sev->vdata->cmdresp_reg);
 
 	/* wait for command completion */
-- 
2.46.0