2020-09-16 20:02:07

by David Brazdil

Subject: [PATCH v3 09/11] kvm: arm64: Mark hyp stack pages reserved

In preparation for unmapping hyp pages from host stage-2, allocate/free hyp
stack using new helpers which automatically mark the pages reserved.

Signed-off-by: David Brazdil <[email protected]>
---
arch/arm64/kvm/arm.c | 49 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 7af9809fa193..58d7d614519b 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1456,13 +1456,58 @@ static int init_subsystems(void)
return err;
}

+/*
+ * Alloc pages and mark them reserved so the kernel never tries to
+ * take them away from the hypervisor.
+ */
+static unsigned long alloc_hyp_pages(gfp_t flags, unsigned int order)
+{
+ struct page *page;
+ unsigned long i;
+
+ page = alloc_pages(flags, order);
+ if (!page)
+ return 0;
+
+ for (i = 0; i < (1ul << order); ++i)
+ mark_page_reserved(page + i);
+
+ return (unsigned long)page_address(page);
+}
+
+static unsigned long alloc_hyp_page(gfp_t flags)
+{
+ return alloc_hyp_pages(flags, 0);
+}
+
+/*
+ * Free pages which were previously marked reserved for the hypervisor.
+ */
+static void free_hyp_pages(unsigned long addr, unsigned int order)
+{
+ unsigned long i;
+ struct page *page;
+
+ if (!addr)
+ return;
+
+ page = virt_to_page(addr);
+ for (i = 0; i < (1ul << order); ++i)
+ free_reserved_page(page + i);
+}
+
+static void free_hyp_page(unsigned long addr)
+{
+ return free_hyp_pages(addr, 0);
+}
+
static void teardown_hyp_mode(void)
{
int cpu;

free_hyp_pgds();
for_each_possible_cpu(cpu)
- free_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
+ free_hyp_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
}

/**
@@ -1486,7 +1531,7 @@ static int init_hyp_mode(void)
for_each_possible_cpu(cpu) {
unsigned long stack_page;

- stack_page = __get_free_page(GFP_KERNEL);
+ stack_page = alloc_hyp_page(GFP_KERNEL);
if (!stack_page) {
err = -ENOMEM;
goto out_err;
--
2.28.0.618.gf4bc123cb7-goog

2020-09-18 12:05:44

by Will Deacon

Subject: Re: [PATCH v3 09/11] kvm: arm64: Mark hyp stack pages reserved

On Wed, Sep 16, 2020 at 06:34:37PM +0100, David Brazdil wrote:
> In preparation for unmapping hyp pages from host stage-2, allocate/free hyp
> stack using new helpers which automatically mark the pages reserved.

Given that this series doesn't get us that the point of having a stage-2 for
the host, I don't see why we need this part yet.

Will

2020-09-22 18:10:32

by David Brazdil

Subject: Re: [PATCH v3 09/11] kvm: arm64: Mark hyp stack pages reserved

On Fri, Sep 18, 2020 at 01:00:44PM +0100, Will Deacon wrote:
> On Wed, Sep 16, 2020 at 06:34:37PM +0100, David Brazdil wrote:
> > In preparation for unmapping hyp pages from host stage-2, allocate/free hyp
> > stack using new helpers which automatically mark the pages reserved.
>
> Given that this series doesn't get us that the point of having a stage-2 for
> the host, I don't see why we need this part yet.
>
> Will

Dropped