Patch "crypto: ccp - Clear PSP interrupt status register before calling handler" has been added to the 6.3-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    crypto: ccp - Clear PSP interrupt status register before calling handler

to the 6.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     crypto-ccp-clear-psp-interrupt-status-register-befor.patch
and it can be found in the queue-6.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 087648bf7a8d2b09a60e90994be7e720c861136a
Author: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx>
Date:   Tue Mar 28 15:16:36 2023 +0000

    crypto: ccp - Clear PSP interrupt status register before calling handler
    
    [ Upstream commit 45121ad4a1750ca47ce3f32bd434bdb0cdbf0043 ]
    
    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@xxxxxxxxxxxxxxx
    Signed-off-by: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx>
    Acked-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
    Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
index c9c741ac84421..949a3fa0b94a9 100644
--- a/drivers/crypto/ccp/psp-dev.c
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -42,6 +42,9 @@ 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)
@@ -51,9 +54,6 @@ static irqreturn_t psp_irq_handler(int irq, void *data)
 			psp->tee_irq_handler(irq, psp->tee_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;
 }