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bhyve: Drop volatile qualifiers from virtio rings

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The qualifiers are there presumably because these rings are mapped into
the guest, but they do not appear to be required for correctness, and
bhyve generally doesn't qualify accesses to guest memory this way.
Moreover, the qualifiers are discarded by snapshot code, causing clang
to emit warnings.  Just stop using volatile here.

MFC after:	2 weeks
Reviewed by:	corvink, jhb
Differential Revision:	https://reviews.freebsd.org/D37291
This commit is contained in:
Mark Johnston 2022-11-11 10:02:10 -05:00
parent 691e23e6c5
commit 593200c23b
2 changed files with 10 additions and 11 deletions
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13
usr.sbin/bhyve/virtio.c
View File

@ -214,10 +214,9 @@ vi_vq_init(struct virtio_softc *vs, uint32_t pfn)
* descriptor.
*/
static inline void
_vq_record(int i, volatile struct vring_desc *vd,
struct vmctx *ctx, struct iovec *iov, int n_iov,
struct vi_req *reqp) {
_vq_record(int i, struct vring_desc *vd, struct vmctx *ctx, struct iovec *iov,
int n_iov, struct vi_req *reqp)
{
if (i >= n_iov)
return;
iov[i].iov_base = paddr_guest2host(ctx, vd->addr, vd->len);
@ -271,7 +270,7 @@ vq_getchain(struct vqueue_info *vq, struct iovec *iov, int niov,
u_int ndesc, n_indir;
u_int idx, next;
struct vi_req req;
volatile struct vring_desc *vdir, *vindir, *vp;
struct vring_desc *vdir, *vindir, *vp;
struct vmctx *ctx;
struct virtio_softc *vs;
const char *name;
@ -409,8 +408,8 @@ vq_retchains(struct vqueue_info *vq, uint16_t n_chains)
void
vq_relchain_prepare(struct vqueue_info *vq, uint16_t idx, uint32_t iolen)
{
volatile struct vring_used *vuh;
volatile struct vring_used_elem *vue;
struct vring_used *vuh;
struct vring_used_elem *vue;
uint16_t mask;
/*

8
usr.sbin/bhyve/virtio.h
View File

@ -314,14 +314,14 @@ struct vqueue_info {
uint32_t vq_pfn; /* PFN of virt queue (not shifted!) */
volatile struct vring_desc *vq_desc; /* descriptor array */
volatile struct vring_avail *vq_avail; /* the "avail" ring */
volatile struct vring_used *vq_used; /* the "used" ring */
struct vring_desc *vq_desc; /* descriptor array */
struct vring_avail *vq_avail; /* the "avail" ring */
struct vring_used *vq_used; /* the "used" ring */
};
/* as noted above, these are sort of backwards, name-wise */
#define VQ_AVAIL_EVENT_IDX(vq) \
(*(volatile uint16_t *)&(vq)->vq_used->ring[(vq)->vq_qsize])
(*(uint16_t *)&(vq)->vq_used->ring[(vq)->vq_qsize])
#define VQ_USED_EVENT_IDX(vq) \
((vq)->vq_avail->ring[(vq)->vq_qsize])