On Tue, 27 Feb 2024, Vikram Garhwal wrote:
> From: Juergen Gross <jgr...@suse.com>
>
> Add the callbacks for mapping/unmapping guest memory via grants to the
> special grant memory region.
>
> Signed-off-by: Juergen Gross <jgr...@suse.com>
> Signed-off-by: Vikram Garhwal <vikram.garh...@amd.com>
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
> ---
> hw/xen/xen-mapcache.c | 176 +++++++++++++++++++++++++++++++++++++++++-
> system/physmem.c | 11 ++-
> 2 files changed, 182 insertions(+), 5 deletions(-)
>
> diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
> index 179b7e95b2..2e4c9b4947 100644
> --- a/hw/xen/xen-mapcache.c
> +++ b/hw/xen/xen-mapcache.c
> @@ -9,6 +9,8 @@
> */
>
> #include "qemu/osdep.h"
> +#include "qemu/queue.h"
> +#include "qemu/thread.h"
> #include "qemu/units.h"
> #include "qemu/error-report.h"
>
> @@ -23,6 +25,8 @@
> #include "sysemu/xen-mapcache.h"
> #include "trace.h"
>
> +#include <xenevtchn.h>
> +#include <xengnttab.h>
>
> #if HOST_LONG_BITS == 32
> # define MCACHE_BUCKET_SHIFT 16
> @@ -377,7 +381,7 @@ uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size,
> return p;
> }
>
> -ram_addr_t xen_ram_addr_from_mapcache(void *ptr)
> +static ram_addr_t xen_ram_addr_from_mapcache_try(void *ptr)
> {
> MapCacheEntry *entry = NULL;
> MapCacheRev *reventry;
> @@ -588,10 +592,179 @@ uint8_t *xen_replace_cache_entry(hwaddr old_phys_addr,
> return p;
> }
>
> +struct XENMappedGrantRegion {
> + void *addr;
> + unsigned int pages;
> + unsigned int refs;
> + unsigned int prot;
> + uint32_t idx;
> + QLIST_ENTRY(XENMappedGrantRegion) list;
> +};
> +
> +static xengnttab_handle *xen_region_gnttabdev;
> +static QLIST_HEAD(GrantRegionList, XENMappedGrantRegion) xen_grant_mappings =
> + QLIST_HEAD_INITIALIZER(xen_grant_mappings);
> +static QemuMutex xen_map_mutex;
> +
> +static void *xen_map_grant_dyn(MemoryRegion **mr, hwaddr addr, hwaddr *plen,
> + bool is_write, MemTxAttrs attrs)
> +{
> + unsigned int page_off = addr & (XC_PAGE_SIZE - 1);
> + unsigned int i;
> + unsigned int total_grants = 0;
> + unsigned int nrefs = (page_off + *plen + XC_PAGE_SIZE - 1) >>
> XC_PAGE_SHIFT;
> + uint32_t ref = (addr - XEN_GRANT_ADDR_OFF) >> XC_PAGE_SHIFT;
> + uint32_t *refs = NULL;
> + unsigned int prot = PROT_READ;
> + struct XENMappedGrantRegion *mgr = NULL;
> +
> + if (is_write) {
> + prot |= PROT_WRITE;
> + }
> +
> + qemu_mutex_lock(&xen_map_mutex);
> +
> + QLIST_FOREACH(mgr, &xen_grant_mappings, list) {
> + if (mgr->idx == ref &&
> + mgr->pages == nrefs &&
> + (mgr->prot & prot) == prot) {
> + break;
> + }
> +
> + total_grants += mgr->pages;
> + }
> +
> + if (!mgr) {
> + if (nrefs + total_grants >= XEN_MAX_VIRTIO_GRANTS) {
> + qemu_mutex_unlock(&xen_map_mutex);
> + return NULL;
> + }
> +
> + mgr = g_new(struct XENMappedGrantRegion, 1);
> +
> + if (nrefs == 1) {
> + refs = &ref;
> + } else {
> + refs = g_new(uint32_t, nrefs);
> + for (i = 0; i < nrefs; i++) {
> + refs[i] = ref + i;
> + }
> + }
> + mgr->addr = xengnttab_map_domain_grant_refs(xen_region_gnttabdev,
> nrefs,
> + xen_domid, refs, prot);
> + if (mgr->addr) {
> + mgr->pages = nrefs;
> + mgr->refs = 1;
> + mgr->prot = prot;
> + mgr->idx = ref;
> +
> + QLIST_INSERT_HEAD(&xen_grant_mappings, mgr, list);
> + } else {
> + g_free(mgr);
> + mgr = NULL;
> + }
> + } else {
> + mgr->refs++;
> + }
> +
> + qemu_mutex_unlock(&xen_map_mutex);
> +
> + if (nrefs > 1) {
> + g_free(refs);
> + }
> +
> + return mgr ? mgr->addr + page_off : NULL;
> +}
> +
> +static void xen_unmap_grant_dyn(MemoryRegion *mr, void *buffer, ram_addr_t
> addr,
> + hwaddr len, bool is_write, hwaddr access_len)
> +{
> + unsigned int page_off = (unsigned long)buffer & (XC_PAGE_SIZE - 1);
> + unsigned int nrefs = (page_off + len + XC_PAGE_SIZE - 1) >>
> XC_PAGE_SHIFT;
> + unsigned int prot = PROT_READ;
> + struct XENMappedGrantRegion *mgr = NULL;
> +
> + if (is_write) {
> + prot |= PROT_WRITE;
> + }
> +
> + qemu_mutex_lock(&xen_map_mutex);
> +
> + QLIST_FOREACH(mgr, &xen_grant_mappings, list) {
> + if (mgr->addr == buffer - page_off &&
> + mgr->pages == nrefs &&
> + (mgr->prot & prot) == prot) {
> + break;
> + }
> + }
> + if (mgr) {
> + mgr->refs--;
> + if (!mgr->refs) {
> + xengnttab_unmap(xen_region_gnttabdev, mgr->addr, nrefs);
> +
> + QLIST_REMOVE(mgr, list);
> + g_free(mgr);
> + }
> + } else {
> + error_report("xen_unmap_grant_dyn() trying to unmap unknown buffer");
> + }
> +
> + qemu_mutex_unlock(&xen_map_mutex);
> +}
> +
> +static ram_addr_t xen_ram_addr_from_grant_cache(void *ptr)
> +{
> + unsigned int page_off = (unsigned long)ptr & (XC_PAGE_SIZE - 1);
> + struct XENMappedGrantRegion *mgr = NULL;
> + ram_addr_t raddr = RAM_ADDR_INVALID;
> +
> + qemu_mutex_lock(&xen_map_mutex);
> +
> + QLIST_FOREACH(mgr, &xen_grant_mappings, list) {
> + if (mgr->addr == ptr - page_off) {
> + break;
> + }
> + }
> +
> + if (mgr) {
> + raddr = (mgr->idx << XC_PAGE_SHIFT) + page_off + XEN_GRANT_ADDR_OFF;
> + }
> +
> + qemu_mutex_unlock(&xen_map_mutex);
> +
> + return raddr;
> +}
> +
> +ram_addr_t xen_ram_addr_from_mapcache(void *ptr)
> +{
> + ram_addr_t raddr;
> +
> + raddr = xen_ram_addr_from_mapcache_try(ptr);
> + if (raddr == RAM_ADDR_INVALID) {
> + raddr = xen_ram_addr_from_grant_cache(ptr);
> + }
> +
> + return raddr;
> +}
> +
> +static const struct MemoryRegionOps xen_grant_mr_ops = {
> + .map = xen_map_grant_dyn,
> + .unmap = xen_unmap_grant_dyn,
> + .endianness = DEVICE_LITTLE_ENDIAN,
> +};
> +
> MemoryRegion *xen_init_grant_ram(void)
> {
> RAMBlock *block;
>
> + qemu_mutex_init(&xen_map_mutex);
> +
> + xen_region_gnttabdev = xengnttab_open(NULL, 0);
> + if (xen_region_gnttabdev == NULL) {
> + fprintf(stderr, "can't open gnttab device\n");
> + return NULL;
> + }
> +
> memory_region_init(&ram_grants, NULL, "xen.grants",
> XEN_MAX_VIRTIO_GRANTS * XC_PAGE_SIZE);
> block = g_malloc0(sizeof(*block));
> @@ -606,6 +779,7 @@ MemoryRegion *xen_init_grant_ram(void)
> ram_grants.ram_block = block;
> ram_grants.ram = true;
> ram_grants.terminates = true;
> + ram_grants.ops = &xen_grant_mr_ops;
> ram_block_add_list(block);
> memory_region_add_subregion(get_system_memory(), XEN_GRANT_ADDR_OFF,
> &ram_grants);
> diff --git a/system/physmem.c b/system/physmem.c
> index d989e9fc1f..e6fc075d8f 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -2232,13 +2232,16 @@ RAMBlock *qemu_ram_block_from_host(void *ptr, bool
> round_offset,
>
> if (xen_enabled()) {
> ram_addr_t ram_addr;
> +
> RCU_READ_LOCK_GUARD();
> ram_addr = xen_ram_addr_from_mapcache(ptr);
> - block = qemu_get_ram_block(ram_addr);
> - if (block) {
> - *offset = ram_addr - block->offset;
> + if (ram_addr != RAM_ADDR_INVALID) {
> + block = qemu_get_ram_block(ram_addr);
> + if (block) {
> + *offset = ram_addr - block->offset;
> + }
> + return block;
> }
> - return block;
> }
>
> RCU_READ_LOCK_GUARD();
> --
> 2.17.1
>
