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KVM: arm64: Back the hypervisor 'struct hyp_page' array for all memory

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The EL2 'vmemmap' array in nVHE Protected mode is currently very sparse:
only memory pages owned by the hypervisor itself have a matching 'struct
hyp_page'. However, as the size of this struct has been reduced
significantly since its introduction, it appears that we can now afford
to back the vmemmap for all of memory.

Having an easily accessible 'struct hyp_page' for every physical page in
memory provides the hypervisor with a simple mechanism to store metadata
(e.g. a refcount) that wouldn't otherwise fit in the very limited number
of software bits available in the host stage-2 page-table entries. This
will be used in subsequent patches when pinning host memory pages for
use by the hypervisor at EL2.

Tested-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221110190259.26861-4-will@kernel.org
This commit is contained in:
Quentin Perret
2022-11-10 19:02:36 +00:00
committed by Marc Zyngier
parent 72a5bc0f15
commit 8e6bcc3a45
6 changed files with 60 additions and 40 deletions
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18
arch/arm64/kvm/pkvm.c
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@@ -53,7 +53,7 @@ static int __init register_memblock_regions(void)
void __init kvm_hyp_reserve(void)
{
u64 nr_pages, prev, hyp_mem_pages = 0;
u64 hyp_mem_pages = 0;
int ret;
if (!is_hyp_mode_available() || is_kernel_in_hyp_mode())
@@ -71,21 +71,7 @@ void __init kvm_hyp_reserve(void)
hyp_mem_pages += hyp_s1_pgtable_pages();
hyp_mem_pages += host_s2_pgtable_pages();
/*
* The hyp_vmemmap needs to be backed by pages, but these pages
* themselves need to be present in the vmemmap, so compute the number
* of pages needed by looking for a fixed point.
*/
nr_pages = 0;
do {
prev = nr_pages;
nr_pages = hyp_mem_pages + prev;
nr_pages = DIV_ROUND_UP(nr_pages * STRUCT_HYP_PAGE_SIZE,
PAGE_SIZE);
nr_pages += __hyp_pgtable_max_pages(nr_pages);
} while (nr_pages != prev);
hyp_mem_pages += nr_pages;
hyp_mem_pages += hyp_vmemmap_pages(STRUCT_HYP_PAGE_SIZE);
/*
* Try to allocate a PMD-aligned region to reduce TLB pressure once