mirror of https://gitee.com/openkylin/qemu.git
a71c775b24
The VPD Block Limits Inquiry page is optional, allowing SCSI devices to not implement it. This is the case for devices like the MegaRAID SAS 9361-8i and Microsemi PM8069. In case of SCSI passthrough, the response of this request is used by the QEMU SCSI layer to set the max_io_sectors that the guest device will support, based on the value of the max_sectors_kb that the device has set in the host at that time. Without this response, the guest kernel is free to assume any value of max_io_sectors for the SCSI device. If this value is greater than the value from the host, SCSI Sense errors will occur because the guest will send read/write requests that are larger than the underlying host device is configured to support. An example of this behavior can be seen in [1]. A workaround is to set the max_sectors_kb host value back in the guest kernel (a process that can be automated using rc.local startup scripts and the like), but this has several drawbacks: - it can be troublesome if the guest has many passthrough devices that needs this tuning; - if a change in max_sectors_kb is made in the host side, manual change in the guests will also be required; - during an OS install it is difficult, and sometimes not possible, to go to a terminal and change the max_sectors_kb prior to the installation. This means that the disk can't be used during the install process. The easiest alternative here is to roll back to scsi-hd, install the guest and then go back to SCSI passthrough when the installation is done and max_sectors_kb can be set. An easier way would be to QEMU handle the absence of the Block Limits VPD device response, setting max_io_sectors accordingly and allowing the guest to use the device without the hassle. This patch adds emulation of the Block Limits VPD response for SCSI passthrough devices of type TYPE_DISK that doesn't support it. The following changes were made: - scsi_handle_inquiry_reply will now check the available VPD pages from the Inquiry EVPD reply. In case the device does not - a new function called scsi_generic_set_vpd_bl_emulation, that is called during device realize, was created to set a new flag 'needs_vpd_bl_emulation' of the device. This function retrieves the Inquiry EVPD response of the device to check for VPD BL support. - scsi_handle_inquiry_reply will now check the available VPD pages from the Inquiry EVPD reply in case the device needs VPD BL emulation, adding the Block Limits page (0xb0) to the list. This will make the guest kernel aware of the support that we're now providing by emulation. - a new function scsi_emulate_block_limits creates the emulated Block Limits response. This function is called inside scsi_read_complete in case the device requires Block Limits VPD emulation and we detected a SCSI Sense error in the VPD Block Limits reply that was issued from the guest kernel to the device. This error is expected: we're reporting support from our side, but the device isn't aware of it. With this patch, the guest now queries the Block Limits page during the device configuration because it is being advertised in the Supported Pages response. It will either receive the Block Limits page from the hardware, if it supports it, or will receive an emulated response from QEMU. At any rate, the guest now has the information to set the max_sectors_kb parameter accordingly, sparing the user of SCSI sense errors that would happen without the emulated response and in the absence of Block Limits support from the hardware. [1] https://bugzilla.redhat.com/show_bug.cgi?id=1566195 Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1566195 Reported-by: Dac Nguyen <dacng@us.ibm.com> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> Message-Id: <20180627172432.11120-4-danielhb413@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| .. | ||
| Makefile.objs | ||
| esp-pci.c | ||
| esp.c | ||
| lsi53c895a.c | ||
| megasas.c | ||
| mfi.h | ||
| mpi.h | ||
| mptconfig.c | ||
| mptendian.c | ||
| mptsas.c | ||
| mptsas.h | ||
| scsi-bus.c | ||
| scsi-disk.c | ||
| scsi-generic.c | ||
| spapr_vscsi.c | ||
| srp.h | ||
| trace-events | ||
| vhost-scsi-common.c | ||
| vhost-scsi.c | ||
| vhost-user-scsi.c | ||
| viosrp.h | ||
| virtio-scsi-dataplane.c | ||
| virtio-scsi.c | ||
| vmw_pvscsi.c | ||
| vmw_pvscsi.h | ||