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KVM: arm64: Implement do_unshare() helper for unsharing memory

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Tearing down a previously shared memory region results in the borrower
losing access to the underlying pages and returning them to the "owned"
state in the owner.

Implement a do_unshare() helper, along the same lines as do_share(), to
provide this functionality for the host-to-hyp case.

Reviewed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211215161232.1480836-13-qperret@google.com
This commit is contained in:
Will Deacon 2021-12-15 16:12:29 +00:00 committed by Marc Zyngier
parent 1ee32109fd
commit 376a240f03
1 changed files with 115 additions and 0 deletions
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115
arch/arm64/kvm/hyp/nvhe/mem_protect.c
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@ -485,6 +485,16 @@ static int host_request_owned_transition(u64 *completer_addr,
return __host_check_page_state_range(addr, size, PKVM_PAGE_OWNED);
}
static int host_request_unshare(u64 *completer_addr,
const struct pkvm_mem_transition *tx)
{
u64 size = tx->nr_pages * PAGE_SIZE;
u64 addr = tx->initiator.addr;
*completer_addr = tx->initiator.host.completer_addr;
return __host_check_page_state_range(addr, size, PKVM_PAGE_SHARED_OWNED);
}
static int host_initiate_share(u64 *completer_addr,
const struct pkvm_mem_transition *tx)
{
@ -495,6 +505,16 @@ static int host_initiate_share(u64 *completer_addr,
return __host_set_page_state_range(addr, size, PKVM_PAGE_SHARED_OWNED);
}
static int host_initiate_unshare(u64 *completer_addr,
const struct pkvm_mem_transition *tx)
{
u64 size = tx->nr_pages * PAGE_SIZE;
u64 addr = tx->initiator.addr;
*completer_addr = tx->initiator.host.completer_addr;
return __host_set_page_state_range(addr, size, PKVM_PAGE_OWNED);
}
static enum pkvm_page_state hyp_get_page_state(kvm_pte_t pte)
{
if (!kvm_pte_valid(pte))
@ -535,6 +555,17 @@ static int hyp_ack_share(u64 addr, const struct pkvm_mem_transition *tx,
return __hyp_check_page_state_range(addr, size, PKVM_NOPAGE);
}
static int hyp_ack_unshare(u64 addr, const struct pkvm_mem_transition *tx)
{
u64 size = tx->nr_pages * PAGE_SIZE;
if (__hyp_ack_skip_pgtable_check(tx))
return 0;
return __hyp_check_page_state_range(addr, size,
PKVM_PAGE_SHARED_BORROWED);
}
static int hyp_complete_share(u64 addr, const struct pkvm_mem_transition *tx,
enum kvm_pgtable_prot perms)
{
@ -545,6 +576,14 @@ static int hyp_complete_share(u64 addr, const struct pkvm_mem_transition *tx,
return pkvm_create_mappings_locked(start, end, prot);
}
static int hyp_complete_unshare(u64 addr, const struct pkvm_mem_transition *tx)
{
u64 size = tx->nr_pages * PAGE_SIZE;
int ret = kvm_pgtable_hyp_unmap(&pkvm_pgtable, addr, size);
return (ret != size) ? -EFAULT : 0;
}
static int check_share(struct pkvm_mem_share *share)
{
const struct pkvm_mem_transition *tx = &share->tx;
@ -621,6 +660,82 @@ static int do_share(struct pkvm_mem_share *share)
return WARN_ON(__do_share(share));
}
static int check_unshare(struct pkvm_mem_share *share)
{
const struct pkvm_mem_transition *tx = &share->tx;
u64 completer_addr;
int ret;
switch (tx->initiator.id) {
case PKVM_ID_HOST:
ret = host_request_unshare(&completer_addr, tx);
break;
default:
ret = -EINVAL;
}
if (ret)
return ret;
switch (tx->completer.id) {
case PKVM_ID_HYP:
ret = hyp_ack_unshare(completer_addr, tx);
break;
default:
ret = -EINVAL;
}
return ret;
}
static int __do_unshare(struct pkvm_mem_share *share)
{
const struct pkvm_mem_transition *tx = &share->tx;
u64 completer_addr;
int ret;
switch (tx->initiator.id) {
case PKVM_ID_HOST:
ret = host_initiate_unshare(&completer_addr, tx);
break;
default:
ret = -EINVAL;
}
if (ret)
return ret;
switch (tx->completer.id) {
case PKVM_ID_HYP:
ret = hyp_complete_unshare(completer_addr, tx);
break;
default:
ret = -EINVAL;
}
return ret;
}
/*
* do_unshare():
*
* The page owner revokes access from another component for a range of
* pages which were previously shared using do_share().
*
* Initiator: SHARED_OWNED => OWNED
* Completer: SHARED_BORROWED => NOPAGE
*/
static int do_unshare(struct pkvm_mem_share *share)
{
int ret;
ret = check_unshare(share);
if (ret)
return ret;
return WARN_ON(__do_unshare(share));
}
int __pkvm_host_share_hyp(u64 pfn)
{
int ret;