linux-kernel - [PATCH] xen-pciback: Consider MSI-X enabled only when MASKALL bit is cleared

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Message-Id: <20221117114122.1588338-1-marmarek@invisiblethingslab.com>
Date:   Thu, 17 Nov 2022 12:41:17 +0100
From:   Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
To:     linux-kernel@...r.kernel.org
Cc:     Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>, Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Jan Beulich <jbeulich@...e.com>,
        xen-devel@...ts.xenproject.org (moderated list:XEN HYPERVISOR INTERFACE)
Subject: [PATCH] xen-pciback: Consider MSI-X enabled only when MASKALL bit is cleared

Linux enables MSI-X before disabling INTx, but keeps MSI-X masked until
the table is filled. Then it disables INTx just before clearing MASKALL
bit. Currently this approach is rejected by xen-pciback.
Allow setting PCI_MSIX_FLAGS_ENABLE while INTx is still enabled as long
as PCI_MSIX_FLAGS_MASKALL is set too.

Fixes: 5e29500eba2a ("xen-pciback: Allow setting PCI_MSIX_FLAGS_MASKALL too")
Signed-off-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
---
 drivers/xen/xen-pciback/conf_space.c            | 2 +-
 drivers/xen/xen-pciback/conf_space_capability.c | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xen-pciback/conf_space.c b/drivers/xen/xen-pciback/conf_space.c
index 059de92aea7d..e8923bffc175 100644
--- a/drivers/xen/xen-pciback/conf_space.c
+++ b/drivers/xen/xen-pciback/conf_space.c
@@ -313,7 +313,7 @@ int xen_pcibk_get_interrupt_type(struct pci_dev *dev)
 				&val);
 		if (err)
 			return err;
-		if (val & PCI_MSIX_FLAGS_ENABLE)
+		if (val & PCI_MSIX_FLAGS_ENABLE && !(val & PCI_MSIX_FLAGS_MASKALL))
 			ret |= INTERRUPT_TYPE_MSIX;
 	}
 	return ret ?: INTERRUPT_TYPE_NONE;
diff --git a/drivers/xen/xen-pciback/conf_space_capability.c b/drivers/xen/xen-pciback/conf_space_capability.c
index 097316a74126..5c851f916ebc 100644
--- a/drivers/xen/xen-pciback/conf_space_capability.c
+++ b/drivers/xen/xen-pciback/conf_space_capability.c
@@ -242,6 +242,10 @@ static int msi_msix_flags_write(struct pci_dev *dev, int offset, u16 new_value,
 		if (int_type == INTERRUPT_TYPE_NONE ||
 		    int_type == field_config->int_type)
 			goto write;
+		if (int_type == INTERRUPT_TYPE_INTX &&
+		    field_config->int_type == INTERRUPT_TYPE_MSIX &&
+		    (new_value & PCI_MSIX_FLAGS_MASKALL))
+			goto write;
 		return PCIBIOS_SET_FAILED;
 	}
 
-- 
2.37.3