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util/vfio-helpers.c: Use ram_block_discard_disable() in qemu_vfio_open_pci()

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Currently, when using "nvme://" for a block device, like
    -drive file=nvme://0000:01:00.0/1,if=none,id=drive0 \
    -device virtio-blk,drive=drive0 \

VFIO may pin all guest memory, and discarding of RAM no longer works as
expected. I was able to reproduce this easily with my
    01:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd
            NVMe SSD Controller SM981/PM981/PM983

Similar to common VFIO, we have to disable it, making sure that:
a) virtio-balloon won't discard any memory ("silently disabled")
b) virtio-mem and nvme:// run mutually exclusive

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20201116105947.9194-1-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Hildenbrand 2020-11-16 11:59:47 +01:00 committed by Paolo Bonzini
parent 2654ace151
commit b430b51395
2 changed files with 20 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
stubs/ram-block.c
View file

@ -1,6 +1,7 @@
#include "qemu/osdep.h"
#include "exec/ramlist.h"
#include "exec/cpu-common.h"
#include "exec/memory.h"
void *qemu_ram_get_host_addr(RAMBlock *rb)
{
@ -29,3 +30,8 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque)
{
return 0;
}
int ram_block_discard_disable(bool state)
{
return 0;
}

14
util/vfio-helpers.c
View file

@ -16,6 +16,7 @@
#include "qapi/error.h"
#include "exec/ramlist.h"
#include "exec/cpu-common.h"
#include "exec/memory.h"
#include "trace.h"
#include "qemu/error-report.h"
#include "standard-headers/linux/pci_regs.h"
@ -494,8 +495,20 @@ QEMUVFIOState *qemu_vfio_open_pci(const char *device, Error **errp)
int r;
QEMUVFIOState *s = g_new0(QEMUVFIOState, 1);
/*
* VFIO may pin all memory inside mappings, resulting it in pinning
* all memory inside RAM blocks unconditionally.
*/
r = ram_block_discard_disable(true);
if (r) {
error_setg_errno(errp, -r, "Cannot set discarding of RAM broken");
g_free(s);
return NULL;
}
r = qemu_vfio_init_pci(s, device, errp);
if (r) {
ram_block_discard_disable(false);
g_free(s);
return NULL;
}
@ -837,4 +850,5 @@ void qemu_vfio_close(QEMUVFIOState *s)
close(s->device);
close(s->group);
close(s->container);
ram_block_discard_disable(false);
}