From 36902417460e3f9f1c63a79d802622fd774f1c30 Mon Sep 17 00:00:00 2001 From: Bernhard Beschow Date: Fri, 13 May 2022 20:09:56 +0200 Subject: [PATCH] hw/ide/piix: Add some documentation to pci_piix3_xen_ide_unplug() The comment is based on commit message ae4d2eb273b167dad748ea4249720319240b1ac2 'xen-platform: add missing disk unplug option'. Since it seems to describe design decisions and limitations that still apply it seems worth having. Signed-off-by: Bernhard Beschow Reviewed-by: Anthony PERARD Message-Id: <20220513180957.90514-3-shentey@gmail.com> Signed-off-by: Anthony PERARD --- hw/ide/piix.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/hw/ide/piix.c b/hw/ide/piix.c index 2345fe9e1d..bc1b37512a 100644 --- a/hw/ide/piix.c +++ b/hw/ide/piix.c @@ -173,6 +173,17 @@ static void pci_piix_ide_realize(PCIDevice *dev, Error **errp) } } +/* + * The Xen HVM unplug protocol [1] specifies a mechanism to allow guests to + * request unplug of 'aux' disks (which is stated to mean all IDE disks, + * except the primary master). + * + * NOTE: The semantics of what happens if unplug of all disks and 'aux' disks + * is simultaneously requested is not clear. The implementation assumes + * that an 'all' request overrides an 'aux' request. + * + * [1] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/misc/hvm-emulated-unplug.pandoc + */ int pci_piix3_xen_ide_unplug(DeviceState *dev, bool aux) { PCIIDEState *pci_ide;