shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-07 19:30:30 +09:00
Code Issues Packages Projects Releases Wiki Activity

ANDROID: KVM: arm64: pkvm: Don't zero shared pages

Browse Source 
The pKVM hypervisor currently zeroes all the pages mapped into guests
when tearing them down for confidentiality reasons. However, for pages
that are shared with the host this is unecessary at best as the content
of memory is already visible. This is particularly bad for non-protected
guests as all their memory is shared with the host by definition.

Add a new flag to distingish pages that solely need to be updated from
an ownership perspective and those that need to be zeroed.

NOTE: We should probably overhaul the teardown procedure at some point
to avoid the proliferation of those flags, but that would require
significant changes so we might not want that in Android 13.

Bug: 223678931
Change-Id: Icefc85a0bdcdf9958e9eb6871c794f68b06a007f
Signed-off-by: Quentin Perret <qperret@google.com>
This commit is contained in:
Quentin Perret
2022-03-14 15:26:38 +00:00
parent c7bd5ae906
commit f6498d73a5
2 changed files with 22 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/kvm/hyp/include/nvhe/memory.h
View File

@@ -12,6 +12,7 @@
* page-table lock due to the lack of atomics at EL2.
*/
#define HOST_PAGE_NEED_POISONING BIT(0)
#define HOST_PAGE_PENDING_RECLAIM BIT(1)
struct hyp_page {
unsigned short refcount;

25
arch/arm64/kvm/hyp/nvhe/mem_protect.c
View File

@@ -292,7 +292,17 @@ static int reclaim_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
return 0;
page = hyp_phys_to_page(kvm_pte_to_phys(pte));
page->flags |= HOST_PAGE_NEED_POISONING;
switch (pkvm_getstate(kvm_pgtable_stage2_pte_prot(pte))) {
case PKVM_PAGE_OWNED:
page->flags |= HOST_PAGE_NEED_POISONING;
fallthrough;
case PKVM_PAGE_SHARED_BORROWED:
case PKVM_PAGE_SHARED_OWNED:
page->flags |= HOST_PAGE_PENDING_RECLAIM;
break;
default:
return -EPERM;
}
return 0;
}
@@ -1873,16 +1883,23 @@ int __pkvm_host_reclaim_page(u64 pfn)
goto unlock;
page = hyp_phys_to_page(addr);
if (!(page->flags & HOST_PAGE_PENDING_RECLAIM)) {
ret = -EPERM;
goto unlock;
}
if (page->flags & HOST_PAGE_NEED_POISONING) {
ret = hyp_zero_page(addr);
if (ret)
goto unlock;
page->flags &= ~HOST_PAGE_NEED_POISONING;
ret = host_stage2_set_owner_locked(addr, PAGE_SIZE, pkvm_host_id);
} else {
ret = -EPERM;
}
ret = host_stage2_set_owner_locked(addr, PAGE_SIZE, pkvm_host_id);
if (ret)
goto unlock;
page->flags &= ~HOST_PAGE_PENDING_RECLAIM;
unlock:
host_unlock_component();