Re: [PATCH v3 24/32] KVM: arm64: Reserve memory for host stage 2

On Thursday 04 Mar 2021 at 19:49:53 (+0000), Will Deacon wrote:

On Tue, Mar 02, 2021 at 02:59:54PM +0000, Quentin Perret wrote:

quoted

Extend the memory pool allocated for the hypervisor to include enough
pages to map all of memory at page granularity for the host stage 2.
While at it, also reserve some memory for device mappings.

Signed-off-by: Quentin Perret <redacted>
---
 arch/arm64/kvm/hyp/include/nvhe/mm.h | 23 ++++++++++++++++++++++-
 arch/arm64/kvm/hyp/nvhe/setup.c      | 12 ++++++++++++
 arch/arm64/kvm/hyp/reserved_mem.c    |  2 ++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mm.h b/arch/arm64/kvm/hyp/include/nvhe/mm.h
index ac0f7fcffd08..411a35db949c 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mm.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mm.h

@@ -53,7 +53,7 @@ static inline unsigned long __hyp_pgtable_max_pages(unsigned long nr_pages)
 	return total;
 }
 
-static inline unsigned long hyp_s1_pgtable_pages(void)
+static inline unsigned long __hyp_pgtable_total_pages(void)
 {
 	unsigned long res = 0, i;
 

@@ -63,9 +63,30 @@ static inline unsigned long hyp_s1_pgtable_pages(void)
 		res += __hyp_pgtable_max_pages(reg->size >> PAGE_SHIFT);
 	}
 
+	return res;
+}
+
+static inline unsigned long hyp_s1_pgtable_pages(void)
+{
+	unsigned long res;
+
+	res = __hyp_pgtable_total_pages();
+
 	/* Allow 1 GiB for private mappings */
 	res += __hyp_pgtable_max_pages(SZ_1G >> PAGE_SHIFT);
 
 	return res;
 }
+
+static inline unsigned long host_s2_mem_pgtable_pages(void)
+{
+	return __hyp_pgtable_total_pages() + 16;

Is this 16 due to the possibility of a concatenated pgd?

Yes it is, to be sure we have a safe upper-bound.

If so, please add a comment to that effect.

Will do, thanks.
Quentin

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