crypto: ccp - do not request interrupt on cmd completion when irqs disabled

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: 8ef9795 ("crypto: ccp: Add panic notifier for SEV/SNP firmware shutdown on kdump")

Based-on-patch-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Amit Shah <amit.shah@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: amit3s

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 */