Allow setting PCI_MSIX_FLAGS_MASKALL too

QubesOS/qubes-issues#4799
QubesOS/qubes-issues#7057
QubesOS/qubes-issues#7052

Author: marmarek

0001-xen-pciback-Allow-setting-PCI_MSIX_FLAGS_MASKALL-too.patch

@@ -0,0 +1,62 @@
+From 16ffd72062cf0e3f8ca98051a78235f4ac37c339 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
+ <marmarek@invisiblethingslab.com>
+Date: Mon, 14 Nov 2022 10:55:35 +0100
+Subject: [PATCH] xen-pciback: Allow setting PCI_MSIX_FLAGS_MASKALL too
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+When Xen domain configures MSI-X, the usual approach is to enable MSI-X
+together with masking all of them via the config space, then fill the
+table and only then clear PCI_MSIX_FLAGS_MASKALL. Allow doing this via
+QEMU running in a stub domain.
+
+Previously, when changing PCI_MSIX_FLAGS_MASKALL was not allowed, the
+whole write was aborted, preventing change to the PCI_MSIX_FLAGS_ENABLE
+bit too.
+
+Note the Xen hypervisor intercepts this write anyway, and may keep the
+PCI_MSIX_FLAGS_MASKALL bit set if it wishes to. It will store the
+guest-requested state and will apply it eventually.
+
+Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
+---
+ drivers/xen/xen-pciback/conf_space_capability.c | 9 ++++++---
+ 1 file changed, 6 insertions(+), 3 deletions(-)
+
+diff --git a/drivers/xen/xen-pciback/conf_space_capability.c b/drivers/xen/xen-pciback/conf_space_capability.c
+index 5e53b4817f16..097316a74126 100644
+--- a/drivers/xen/xen-pciback/conf_space_capability.c
++++ b/drivers/xen/xen-pciback/conf_space_capability.c
+@@ -190,13 +190,16 @@ static const struct config_field caplist_pm[] = {
+ };
+ 
+ static struct msi_msix_field_config {
+-	u16          enable_bit; /* bit for enabling MSI/MSI-X */
+-	unsigned int int_type;   /* interrupt type for exclusiveness check */
++	u16          enable_bit;   /* bit for enabling MSI/MSI-X */
++	u16          allowed_bits; /* bits allowed to be changed */
++	unsigned int int_type;     /* interrupt type for exclusiveness check */
+ } msi_field_config = {
+ 	.enable_bit	= PCI_MSI_FLAGS_ENABLE,
++	.allowed_bits	= PCI_MSI_FLAGS_ENABLE,
+ 	.int_type	= INTERRUPT_TYPE_MSI,
+ }, msix_field_config = {
+ 	.enable_bit	= PCI_MSIX_FLAGS_ENABLE,
++	.allowed_bits	= PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL,
+ 	.int_type	= INTERRUPT_TYPE_MSIX,
+ };
+ 
+@@ -229,7 +232,7 @@ static int msi_msix_flags_write(struct pci_dev *dev, int offset, u16 new_value,
+ 		return 0;
+ 
+ 	if (!dev_data->allow_interrupt_control ||
+-	    (new_value ^ old_value) & ~field_config->enable_bit)
++	    (new_value ^ old_value) & ~field_config->allowed_bits)
+ 		return PCIBIOS_SET_FAILED;
+ 
+ 	if (new_value & field_config->enable_bit) {
+-- 
+2.37.3
+

kernel.spec.in

@@ -146,6 +146,7 @@ Patch12: 0013-xen-pcifront-pciback-Update-pciif.h-with-err-and-res.patch
 Patch16: 0001-usbip-tweak-clear-halt-with-simple-reset.patch
 Patch19: increase-reclaim-speed.patch
 Patch25: 0001-Re-enable-interrupts-before-loading-PNVM.patch
+Patch26: 0001-xen-pciback-Allow-setting-PCI_MSIX_FLAGS_MASKALL-too.patch
 
 %description
 Qubes Dom0 kernel.