FAILED: patch "[PATCH] crypto: ccp - Clear PSP interrupt status register before" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 45121ad4a1750ca47ce3f32bd434bdb0cdbf0043
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023050637-deuce-matcher-74ad@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 45121ad4a1750ca47ce3f32bd434bdb0cdbf0043 Mon Sep 17 00:00:00 2001
From: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
Date: Tue, 28 Mar 2023 15:16:36 +0000
Subject: [PATCH] crypto: ccp - Clear PSP interrupt status register before
 calling handler

The PSP IRQ is edge-triggered (MSI or MSI-X) in all cases supported by
the psp module so clear the interrupt status register early in the
handler to prevent missed interrupts. sev_irq_handler() calls wake_up()
on a wait queue, which can result in a new command being submitted from
a different CPU. This then races with the clearing of isr and can result
in missed interrupts. A missed interrupt results in a command waiting
until it times out, which results in the psp being declared dead.

This is unlikely on bare metal, but has been observed when running
virtualized. In the cases where this is observed, sev->cmdresp_reg has
PSP_CMDRESP_RESP set which indicates that the command was processed
correctly but no interrupt was asserted.

The full sequence of events looks like this:

CPU 1: submits SEV cmd #1
CPU 1: calls wait_event_timeout()
CPU 0: enters psp_irq_handler()
CPU 0: calls sev_handler()->wake_up()
CPU 1: wakes up; finishes processing cmd #1
CPU 1: submits SEV cmd #2
CPU 1: calls wait_event_timeout()
PSP:   finishes processing cmd #2; interrupt status is still set; no interrupt
CPU 0: clears intsts
CPU 0: exits psp_irq_handler()
CPU 1: wait_event_timeout() times out; psp_dead=true

Fixes: 200664d5237f ("crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support")
Cc: stable@vger.kernel.org
Signed-off-by: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
index ec98f19800de..e3d6955d3265 100644
--- a/drivers/crypto/ccp/psp-dev.c
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -43,15 +43,15 @@ static irqreturn_t psp_irq_handler(int irq, void *data)
 	/* Read the interrupt status: */
 	status = ioread32(psp->io_regs + psp->vdata->intsts_reg);
 
+	/* Clear the interrupt status by writing the same value we read. */
+	iowrite32(status, psp->io_regs + psp->vdata->intsts_reg);
+
 	/* invoke subdevice interrupt handlers */
 	if (status) {
 		if (psp->sev_irq_handler)
 			psp->sev_irq_handler(irq, psp->sev_irq_data, status);
 	}
 
-	/* Clear the interrupt status by writing the same value we read. */
-	iowrite32(status, psp->io_regs + psp->vdata->intsts_reg);
-
 	return IRQ_HANDLED;
 }